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<!doctype birddoc system>
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<!--
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	BIRD 2.0 documentation
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This documentation can have 4 forms: sgml (this is master copy), html, ASCII
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text and dvi/postscript (generated from sgml using sgmltools). You should always
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edit master copy.
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This is a slightly modified linuxdoc dtd. Anything in <descrip> tags is
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considered definition of configuration primitives, <cf> is fragment of
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configuration within normal text, <m> is "meta" information within fragment of
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configuration - something in config which is not keyword.
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    (set-fill-column 80)
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    Copyright 1999,2000 Pavel Machek <pavel@ucw.cz>, distribute under GPL version 2 or later.
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 -->
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<book>
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<title>BIRD 2.0 User's Guide
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<author>
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Ondrej Filip <it/&lt;feela@network.cz&gt;/,
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Pavel Machek <it/&lt;pavel@ucw.cz&gt;/,
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Martin Mares <it/&lt;mj@ucw.cz&gt;/,
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Jan Matejka <it/&lt;mq@jmq.cz&gt;/,
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Ondrej Zajicek <it/&lt;santiago@crfreenet.org&gt;/
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</author>
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<abstract>
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This document contains user documentation for the BIRD Internet Routing Daemon project.
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</abstract>
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<!-- Table of contents -->
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<toc>
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<!-- Begin the document -->
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<chapt>Introduction
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<label id="intro">
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<sect>What is BIRD
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<label id="what-is-bird">
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<p>The name `BIRD' is actually an acronym standing for `BIRD Internet Routing
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Daemon'. Let's take a closer look at the meaning of the name:
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<p><em/BIRD/: Well, we think we have already explained that. It's an acronym
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standing for `BIRD Internet Routing Daemon', you remember, don't you? :-)
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<p><em/Internet Routing/: It's a program (well, a daemon, as you are going to
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discover in a moment) which works as a dynamic router in an Internet type
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network (that is, in a network running either the IPv4 or the IPv6 protocol).
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Routers are devices which forward packets between interconnected networks in
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order to allow hosts not connected directly to the same local area network to
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communicate with each other. They also communicate with the other routers in the
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Internet to discover the topology of the network which allows them to find
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optimal (in terms of some metric) rules for forwarding of packets (which are
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called routing tables) and to adapt themselves to the changing conditions such
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as outages of network links, building of new connections and so on. Most of
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these routers are costly dedicated devices running obscure firmware which is
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hard to configure and not open to any changes (on the other hand, their special
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hardware design allows them to keep up with lots of high-speed network
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interfaces, better than general-purpose computer does). Fortunately, most
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operating systems of the UNIX family allow an ordinary computer to act as a
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router and forward packets belonging to the other hosts, but only according to a
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statically configured table.
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<p>A <em/Routing Daemon/ is in UNIX terminology a non-interactive program
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running on background which does the dynamic part of Internet routing, that is
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it communicates with the other routers, calculates routing tables and sends them
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to the OS kernel which does the actual packet forwarding. There already exist
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other such routing daemons: routed (RIP only), GateD (non-free),
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<HTMLURL URL="http://www.zebra.org" name="Zebra"> and
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<HTMLURL URL="http://sourceforge.net/projects/mrt" name="MRTD">,
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but their capabilities are limited and they are relatively hard to configure
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and maintain.
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<p>BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings,
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to support all the routing technology used in the today's Internet or planned to
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be used in near future and to have a clean extensible architecture allowing new
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routing protocols to be incorporated easily. Among other features, BIRD
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supports:
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<itemize>
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	<item>both IPv4 and IPv6 protocols
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	<item>multiple routing tables
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	<item>the Border Gateway Protocol (BGPv4)
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	<item>the Routing Information Protocol (RIPv2, RIPng)
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	<item>the Open Shortest Path First protocol (OSPFv2, OSPFv3)
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	<item>the Babel Routing Protocol
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	<item>the Router Advertisements for IPv6 hosts
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	<item>a virtual protocol for exchange of routes between different
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		routing tables on a single host
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	<item>a command-line interface allowing on-line control and inspection
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		of status of the daemon
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	<item>soft reconfiguration (no need to use complex online commands to
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		change the configuration, just edit the configuration file and
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		notify BIRD to re-read it and it will smoothly switch itself to
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		the new configuration, not disturbing routing protocols unless
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		they are affected by the configuration changes)
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	<item>a powerful language for route filtering
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</itemize>
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<p>BIRD has been developed at the Faculty of Math and Physics, Charles
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University, Prague, Czech Republic as a student project. It can be freely
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distributed under the terms of the GNU General Public License.
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<p>BIRD has been designed to work on all UNIX-like systems. It has been
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developed and tested under Linux 2.0 to 2.6, and then ported to FreeBSD, NetBSD
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and OpenBSD, porting to other systems (even non-UNIX ones) should be relatively
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easy due to its highly modular architecture.
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<p>BIRD 1.x supported either IPv4 or IPv6 protocol, but had to be compiled separately
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for each one. BIRD~2 supports both of them with a possibility of further extension.
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BIRD~2 supports Linux at least 3.16, FreeBSD 10, NetBSD 7.0, and OpenBSD 5.8.
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Anyway, it will probably work well also on older systems.
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<sect>Installing BIRD
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<label id="install">
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<p>On a recent UNIX system with GNU development tools (GCC, binutils, m4, make)
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and Perl, installing BIRD should be as easy as:
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<code>
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	./configure
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	make
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	make install
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	vi /usr/local/etc/bird.conf
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	bird
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</code>
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<p>You can use <tt>./configure --help</tt> to get a list of configure
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options. The most important ones are: <tt/--with-protocols=/ to produce a slightly smaller
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BIRD executable by configuring out routing protocols you don't use, and
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<tt/--prefix=/ to install BIRD to a place different from <file>/usr/local</file>.
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<sect>Running BIRD
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<label id="argv">
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<p>You can pass several command-line options to bird:
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<descrip>
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	<tag><label id="argv-config">-c <m/config name/</tag>
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	use given configuration file instead of <it/prefix/<file>/etc/bird.conf</file>.
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	<tag><label id="argv-debug">-d</tag>
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	enable debug messages and run bird in foreground.
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	<tag><label id="argv-log-file">-D <m/filename of debug log/</tag>
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	log debugging information to given file instead of stderr.
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	<tag><label id="argv-foreground">-f</tag>
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	run bird in foreground.
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	<tag><label id="argv-group">-g <m/group/</tag>
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	use that group ID, see the next section for details.
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	<tag><label id="argv-help">-h, --help</tag>
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	display command-line options to bird.
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	<tag><label id="argv-local">-l</tag>
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	look for a configuration file and a communication socket in the current
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	working directory instead of in default system locations. However, paths
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	specified by options <cf/-c/, <cf/-s/ have higher priority.
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	<tag><label id="argv-parse">-p</tag>
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	just parse the config file and exit. Return value is zero if the config
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	file is valid, nonzero if there are some errors.
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	<tag><label id="argv-pid">-P <m/name of PID file/</tag>
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	create a PID file with given filename.
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	<tag><label id="argv-recovery">-R</tag>
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	apply graceful restart recovery after start.
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	<tag><label id="argv-socket">-s <m/name of communication socket/</tag>
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	use given filename for a socket for communications with the client,
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	default is <it/prefix/<file>/var/run/bird.ctl</file>.
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	<tag><label id="argv-user">-u <m/user/</tag>
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	drop privileges and use that user ID, see the next section for details.
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	<tag><label id="argv-version">--version</tag>
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	display bird version.
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</descrip>
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<p>BIRD writes messages about its work to log files or syslog (according to config).
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<sect>Privileges
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<label id="privileges">
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<p>BIRD, as a routing daemon, uses several privileged operations (like setting
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routing table and using raw sockets). Traditionally, BIRD is executed and runs
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with root privileges, which may be prone to security problems. The recommended
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way is to use a privilege restriction (options <cf/-u/, <cf/-g/). In that case
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BIRD is executed with root privileges, but it changes its user and group ID to
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an unprivileged ones, while using Linux capabilities to retain just required
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privileges (capabilities CAP_NET_*). Note that the control socket is created
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before the privileges are dropped, but the config file is read after that. The
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privilege restriction is not implemented in BSD port of BIRD.
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<p>An unprivileged user (as an argument to <cf/-u/ options) may be the user
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<cf/nobody/, but it is suggested to use a new dedicated user account (like
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<cf/bird/). The similar considerations apply for the group option, but there is
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one more condition -- the users in the same group can use <file/birdc/ to
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control BIRD.
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<p>Finally, there is a possibility to use external tools to run BIRD in an
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environment with restricted privileges. This may need some configuration, but it
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is generally easy -- BIRD needs just the standard library, privileges to read
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the config file and create the control socket and the CAP_NET_* capabilities.
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<chapt>Architecture
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<label id="architecture">
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<sect>Routing tables
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<label id="routing-tables">
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<p>The heart of BIRD is a routing table. BIRD has several independent routing tables;
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each of them contains routes of exactly one <m/nettype/ (see below). There are two
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default tables -- <cf/master4/ for IPv4 routes and <cf/master6/ for IPv6 routes.
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Other tables must be explicitly configured.
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<p>
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These routing tables are not kernel forwarding tables. No forwarding is done by
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BIRD. If you want to forward packets using the routes in BIRD tables, you may
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use the Kernel protocol (see below) to synchronize them with kernel FIBs.
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<p>
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Every nettype defines a (kind of) primary key on routes. Every route source can
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supply one route for every possible primary key; new route announcement replaces
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the old route from the same source, keeping other routes intact. BIRD always
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chooses the best route for each primary key among the known routes and keeps the
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others as suboptimal. When the best route is retracted, BIRD re-runs the best
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route selection algorithm to find the current best route.
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<p>
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The global best route selection algorithm is (roughly) as follows:
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<itemize>
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	<item>Preferences of the routes are compared.
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	<item>Source protocol instance preferences are compared.
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	<item>If source protocols are the same (e.g. BGP vs. BGP), the protocol's route selection algorithm is invoked.
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	<item>If source protocols are different (e.g. BGP vs. OSPF), result of the algorithm is undefined.
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</itemize>
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<p><label id="dsc-table-sorted">Usually, a routing table just chooses a selected
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route from a list of entries for one network. But if the <cf/sorted/ option is
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activated, these lists of entries are kept completely sorted (according to
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preference or some protocol-dependent metric). This is needed for some features
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of some protocols (e.g. <cf/secondary/ option of BGP protocol, which allows to
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accept not just a selected route, but the first route (in the sorted list) that
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is accepted by filters), but it is incompatible with some other features (e.g.
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<cf/deterministic med/ option of BGP protocol, which activates a way of choosing
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selected route that cannot be described using comparison and ordering). Minor
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advantage is that routes are shown sorted in <cf/show route/, minor disadvantage
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is that it is slightly more computationally expensive.
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<sect>Routes and network types
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<label id="routes">
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<p>BIRD works with several types of routes. Some of them are typical IP routes,
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others are better described as forwarding rules. We call them all routes,
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regardless of this difference.
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<p>Every route consists of several attributes (read more about them in the
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<ref id="route-attributes" name="Route attributes"> section); the common for all
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routes are:
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<itemize>
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	<item>IP address of router which told us about this route
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	<item>Source protocol instance
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	<item>Route preference
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	<item>Optional attributes defined by protocols
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</itemize>
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<p>Other attributes depend on nettypes. Some of them are part of the primary key, these are marked (PK).
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<sect1>IPv4 and IPv6 routes
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<label id="ip-routes">
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<p>The traditional routes. Configuration keywords are <cf/ipv4/ and <cf/ipv6/.
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<itemize>
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	<item>(PK) Route destination (IP prefix together with its length)
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	<item>Route next hops (see below)
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</itemize>
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<sect1>VPN IPv4 and IPv6 routes
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<label id="vpn-routes">
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<p>Routes for IPv4 and IPv6 with VPN Route Distinguisher (<rfc id="4364">).
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Configuration keywords are <cf/vpn4/ and <cf/vpn6/.
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<itemize>
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	<item>(PK) Route destination (IP prefix together with its length)
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	<item>(PK) Route distinguisher (according to <rfc id="4364">)
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	<item>Route next hops
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</itemize>
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<sect1>Route Origin Authorization for IPv4 and IPv6
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<label id="roa-routes">
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<p>These entries can be used to validate route origination of BGP routes.
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A ROA entry specifies prefixes which could be originated by an AS number.
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Their keywords are <cf/roa4/ and <cf/roa6/.
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<itemize>
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	<item>(PK) IP prefix together with its length
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	<item>(PK) Matching prefix maximal length
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	<item>(PK) AS number
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</itemize>
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<sect1>Flowspec for IPv4 and IPv6
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<label id="flow-routes">
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<p>Flowspec rules are a form of firewall and traffic flow control rules
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distributed mostly via BGP. These rules may help the operators stop various
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network attacks in the beginning before eating up the whole bandwidth.
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Configuration keywords are <cf/flow4/ and <cf/flow6/.
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<itemize>
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	<item>(PK) IP prefix together with its length
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	<item>(PK) Flow definition data
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	<item>Flow action (encoded internally as BGP communities according to <rfc id="5575">)
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</itemize>
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<sect1>MPLS switching rules
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<label id="mpls-routes">
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<p>This nettype is currently a stub before implementing more support of <rfc id="3031">.
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BIRD currently does not support any label distribution protocol nor any label assignment method.
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Only the Kernel, Pipe and Static protocols can use MPLS tables.
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Configuration keyword is <cf/mpls/.
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<itemize>
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	<item>(PK) MPLS label
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	<item>Route next hops
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</itemize>
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<sect1>Route next hops
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<label id="route-next-hop">
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<p>This is not a nettype. The route next hop is a complex attribute common for many
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nettypes as you can see before. Every next hop has its assigned device
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(either assumed from its IP address or set explicitly). It may have also
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an IP address and an MPLS stack (one or both independently).
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Maximal MPLS stack depth is set (in compile time) to 8 labels.
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<p>Every route (when eligible to have a next hop) can have more than one next hop.
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In that case, every next hop has also its weight.
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<sect>Protocols and channels
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<label id="protocols-concept">
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<p>BIRD protocol is an abstract class of producers and consumers of the routes.
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Each protocol may run in multiple instances and bind on one side to route
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tables via channels, on the other side to specified listen sockets (BGP),
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interfaces (Babel, OSPF, RIP), APIs (Kernel, Direct), or nothing (Static, Pipe).
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<p>There are also two protocols that do not have any channels -- BFD and Device.
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Both of them are kind of service for other protocols.
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<p>Each protocol is connected to a routing table through a channel. Some protocols
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support only one channel (OSPF, RIP), some protocols support more channels (BGP, Direct).
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Each channel has two filters which can accept, reject and modify the routes.
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An <it/export/ filter is applied to routes passed from the routing table to the protocol,
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an <it/import/ filter is applied to routes in the opposite direction.
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<sect>Graceful restart
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<label id="graceful-restart">
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<p>When BIRD is started after restart or crash, it repopulates routing tables in
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an uncoordinated manner, like after clean start. This may be impractical in some
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cases, because if the forwarding plane (i.e. kernel routing tables) remains
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intact, then its synchronization with BIRD would temporarily disrupt packet
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forwarding until protocols converge. Graceful restart is a mechanism that could
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help with this issue. Generally, it works by starting protocols and letting them
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repopulate routing tables while deferring route propagation until protocols
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acknowledge their convergence. Note that graceful restart behavior have to be
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configured for all relevant protocols and requires protocol-specific support
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(currently implemented for Kernel and BGP protocols), it is activated for
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particular boot by option <cf/-R/.
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<chapt>Configuration
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<label id="config">
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<sect>Introduction
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<label id="config-intro">
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<p>BIRD is configured using a text configuration file. Upon startup, BIRD reads
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<it/prefix/<file>/etc/bird.conf</file> (unless the <tt/-c/ command line option
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is given). Configuration may be changed at user's request: if you modify the
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config file and then signal BIRD with <tt/SIGHUP/, it will adjust to the new
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config. Then there's the client which allows you to talk with BIRD in an
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extensive way.
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<p>In the config, everything on a line after <cf/#/ or inside <cf>/* */</cf> is
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a comment, whitespace characters are treated as a single space. If there's a
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variable number of options, they are grouped using the <cf/{ }/ brackets. Each
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option is terminated by a <cf/;/. Configuration is case sensitive. There are two
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ways how to name symbols (like protocol names, filter names, constants etc.).
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You can either use a simple string starting with a letter followed by any
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combination of letters and numbers (e.g. <cf/R123/, <cf/myfilter/, <cf/bgp5/) or
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you can enclose the name into apostrophes (<cf/'/) and than you can use any
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combination of numbers, letters. hyphens, dots and colons (e.g.
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<cf/'1:strange-name'/, <cf/'-NAME-'/, <cf/'cool::name'/).
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<p>Here is an example of a simple config file. It enables synchronization of
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routing tables with OS kernel, learns network interfaces and runs RIP on all
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network interfaces found.
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<code>
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protocol kernel {
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	ipv4 {
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		export all;	# Default is export none
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	};
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	persist;		# Don't remove routes on BIRD shutdown
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}
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protocol device {
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}
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protocol rip {
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	ipv4 {
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		import all;
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		export all;
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	};
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	interface "*";
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}
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</code>
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<sect>Global options
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<label id="global-opts">
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<p><descrip>
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	<tag><label id="opt-include">include "<m/filename/";</tag>
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	This statement causes inclusion of a new file. The <m/filename/ could
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	also be a wildcard, in that case matching files are included in
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	alphabetic order. The maximal depth is 8. Note that this statement can
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	be used anywhere in the config file, even inside other options, but
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	always on the beginning of line. In the following example, the first
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	semicolon belongs to the <cf/include/, the second to <cf/ipv6 table/.
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	If the <file/tablename.conf/ contains exactly one token (the name of the
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	table), this construction is correct:
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<code>
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ipv6 table
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include "tablename.conf";;
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</code>
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	<tag><label id="opt-log">log "<m/filename/"|syslog [name <m/name/]|stderr all|{ <m/list of classes/ }</tag>
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	Set logging of messages having the given class (either <cf/all/ or
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	<cf/{ error|trace [, <m/.../] }/ etc.) into selected destination (a file specified
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	as a filename string, syslog with optional name argument, or the stderr
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	output). Classes are:
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	<cf/info/, <cf/warning/, <cf/error/ and <cf/fatal/ for messages about local problems,
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	<cf/debug/ for debugging messages,
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	<cf/trace/ when you want to know what happens in the network,
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	<cf/remote/ for messages about misbehavior of remote machines,
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	<cf/auth/ about authentication failures,
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	<cf/bug/ for internal BIRD bugs.
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	You may specify more than one <cf/log/ line to establish logging to
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	multiple destinations. Default: log everything to the system log.
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	<tag><label id="opt-debug-protocols">debug protocols all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
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	Set global defaults of protocol debugging options. See <cf/debug/ in the
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	following section. Default: off.
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	<tag><label id="opt-debug-commands">debug commands <m/number/</tag>
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	Control logging of client connections (0 for no logging, 1 for logging
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	of connects and disconnects, 2 and higher for logging of all client
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	commands). Default: 0.
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	<tag><label id="opt-debug-latency">debug latency <m/switch/</tag>
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	Activate tracking of elapsed time for internal events. Recent events
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	could be examined using <cf/dump events/ command. Default: off.
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	<tag><label id="opt-debug-latency-limit">debug latency limit <m/time/</tag>
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	If <cf/debug latency/ is enabled, this option allows to specify a limit
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	for elapsed time. Events exceeding the limit are logged. Default: 1 s.
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	<tag><label id="opt-watchdog-warn">watchdog warning <m/time/</tag>
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	Set time limit for I/O loop cycle. If one iteration took more time to
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	complete, a warning is logged. Default: 5 s.
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	<tag><label id="opt-watchdog-timeout">watchdog timeout <m/time/</tag>
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	Set time limit for I/O loop cycle. If the limit is breached, BIRD is
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	killed by abort signal. The timeout has effective granularity of
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	seconds, zero means disabled. Default: disabled (0).
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	<tag><label id="opt-mrtdump">mrtdump "<m/filename/"</tag>
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	Set MRTdump file name. This option must be specified to allow MRTdump
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	feature. Default: no dump file.
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	<tag><label id="opt-mrtdump-protocols">mrtdump protocols all|off|{ states|messages [, <m/.../] }</tag>
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	Set global defaults of MRTdump options. See <cf/mrtdump/ in the
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	following section. Default: off.
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	<tag><label id="opt-filter">filter <m/name local variables/{ <m/commands/ }</tag>
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	Define a filter. You can learn more about filters in the following
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	chapter.
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	<tag><label id="opt-function">function <m/name/ (<m/parameters/) <m/local variables/ { <m/commands/ }</tag>
513
	Define a function. You can learn more about functions in the following chapter.
514

    
515
	<tag><label id="opt-protocol">protocol rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
516
	Define a protocol instance called <cf><m/name/</cf> (or with a name like
517
	"rip5" generated automatically if you don't specify any
518
	<cf><m/name/</cf>). You can learn more about configuring protocols in
519
	their own chapters. When <cf>from <m/name2/</cf> expression is used,
520
	initial protocol options are taken from protocol or template
521
	<cf><m/name2/</cf> You can run more than one instance of most protocols
522
	(like RIP or BGP). By default, no instances are configured.
523

    
524
	<tag><label id="opt-template">template rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
525
	Define a protocol template instance called <m/name/ (or with a name like
526
	"bgp1" generated automatically if you don't specify any	<m/name/).
527
	Protocol templates can be used to group common options when many
528
	similarly configured protocol instances are to be defined. Protocol
529
	instances (and other templates) can use templates by using <cf/from/
530
	expression and the name of the template. At the moment templates (and
531
	<cf/from/ expression) are not implemented for OSPF protocol.
532

    
533
	<tag><label id="opt-define">define <m/constant/ = <m/expression/</tag>
534
	Define a constant. You can use it later in every place you could use a
535
	value of the same type. Besides, there are some predefined numeric
536
	constants based on /etc/iproute2/rt_* files. A list of defined constants
537
	can be seen (together with other symbols) using 'show symbols' command.
538

    
539
	<tag><label id="opt-router-id">router id <m/IPv4 address/</tag>
540
	Set BIRD's router ID. It's a world-wide unique identification of your
541
	router, usually one of router's IPv4 addresses. Default: the lowest
542
	IPv4 address of a non-loopback interface.
543

    
544
	<tag><label id="opt-router-id-from">router id from [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../]</tag>
545
	Set BIRD's router ID based on an IPv4 address of an interface specified by
546
	an interface pattern.
547
	See <ref id="proto-iface" name="interface"> section for detailed
548
	description of interface patterns with extended clauses.
549

    
550
	<tag><label id="opt-graceful-restart">graceful restart wait <m/number/</tag>
551
	During graceful restart recovery, BIRD waits for convergence of routing
552
	protocols. This option allows to specify a timeout for the recovery to
553
	prevent waiting indefinitely if some protocols cannot converge. Default:
554
	240 seconds.
555

    
556
	<tag><label id="opt-timeformat">timeformat route|protocol|base|log "<m/format1/" [<m/limit/ "<m/format2/"]</tag>
557
	This option allows to specify a format of date/time used by BIRD. The
558
	first argument specifies for which purpose such format is used.
559
	<cf/route/ is a format used in 'show route' command output,
560
	<cf/protocol/ is used in 'show protocols' command output, <cf/base/ is
561
	used for other commands and <cf/log/ is used in a log file.
562

    
563
	"<m/format1/" is a format string using <it/strftime(3)/ notation (see
564
	<it/man strftime/ for details). It is extended to support sub-second
565
	time part with variable precision (up to microseconds) using "%f"
566
	conversion code (e.g., "%T.%3f" is hh:mm:ss.sss time). <m/limit/ and
567
	"<m/format2/" allow to specify the second format string for times in
568
	past deeper than <m/limit/ seconds.
569

    
570
	There are several shorthands: <cf/iso long/ is a ISO 8601 date/time
571
	format (YYYY-MM-DD hh:mm:ss) that can be also specified using <cf/"%F
572
	%T"/. Similarly, <cf/iso long ms/ and <cf/iso long us/ are ISO 8601
573
	date/time formats with millisecond or microsecond precision.
574
	<cf/iso short/ is a variant of ISO 8601 that uses just the time format
575
	(hh:mm:ss) for near times (up to 20 hours in the past) and the date
576
	format (YYYY-MM-DD) for far times. This is a shorthand for <cf/"%T"
577
	72000 "%F"/. And there are also <cf/iso short ms/ and <cf/iso short us/
578
	high-precision variants of that.
579

    
580
	By default, BIRD uses the <cf/iso short ms/ format for <cf/route/ and
581
	<cf/protocol/ times, and the <cf/iso long ms/ format for <cf/base/ and
582
	<cf/log/ times.
583

    
584
	<tag><label id="opt-table"><m/nettype/ table <m/name/ [sorted]</tag>
585
	Create a new routing table. The default routing tables <cf/master4/ and
586
	<cf/master6/ are created implicitly, other routing tables have to be
587
	added by this command.  Option <cf/sorted/ can be used to enable sorting
588
	of routes, see <ref id="dsc-table-sorted" name="sorted table">
589
	description for details.
590

    
591
	<tag><label id="opt-eval">eval <m/expr/</tag>
592
	Evaluates given filter expression. It is used by the developers for testing of filters.
593
</descrip>
594

    
595

    
596
<sect>Protocol options
597
<label id="protocol-opts">
598

    
599
<p>For each protocol instance, you can configure a bunch of options. Some of
600
them (those described in this section) are generic, some are specific to the
601
protocol (see sections talking about the protocols).
602

    
603
<p>Several options use a <m/switch/ argument. It can be either <cf/on/,
604
<cf/yes/ or a numeric expression with a non-zero value for the option to be
605
enabled or <cf/off/, <cf/no/ or a numeric expression evaluating to zero to
606
disable it. An empty <m/switch/ is equivalent to <cf/on/ ("silence means
607
agreement").
608

    
609
<descrip>
610
	<tag><label id="proto-disabled">disabled <m/switch/</tag>
611
	Disables the protocol. You can change the disable/enable status from the
612
	command line interface without needing to touch the configuration.
613
	Disabled protocols are not activated. Default: protocol is enabled.
614

    
615
	<tag><label id="proto-debug">debug all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
616
	Set protocol debugging options. If asked, each protocol is capable of
617
	writing trace messages about its work to the log (with category
618
	<cf/trace/). You can either request printing of <cf/all/ trace messages
619
	or only of the types selected: <cf/states/ for protocol state changes
620
	(protocol going up, down, starting, stopping etc.), <cf/routes/ for
621
	routes exchanged with the routing table, <cf/filters/ for details on
622
	route filtering, <cf/interfaces/ for interface change events sent to the
623
	protocol, <cf/events/ for events internal to the protocol and <cf/packets/
624
	for packets sent and received by the protocol. Default: off.
625

    
626
	<tag><label id="proto-mrtdump">mrtdump all|off|{ states|messages [, <m/.../] }</tag>
627
	Set protocol MRTdump flags. MRTdump is a standard binary format for
628
	logging information from routing protocols and daemons. These flags
629
	control what kind of information is logged from the protocol to the
630
	MRTdump file (which must be specified by global <cf/mrtdump/ option, see
631
	the previous section). Although these flags are similar to flags of
632
	<cf/debug/ option, their meaning is different and protocol-specific. For
633
	BGP protocol, <cf/states/ logs BGP state changes and <cf/messages/ logs
634
	received BGP messages. Other protocols does not support MRTdump yet.
635

    
636
	<tag><label id="proto-router-id">router id <m/IPv4 address/</tag>
637
	This option can be used to override global router id for a given
638
	protocol. Default: uses global router id.
639

    
640
	<tag><label id="proto-description">description "<m/text/"</tag>
641
	This is an optional description of the protocol. It is displayed as a
642
	part of the output of 'show route all' command.
643

    
644
	<tag><label id="proto-vrf">vrf "<m/text/"</tag>
645
	Associate the protocol with specific VRF. The protocol will be
646
	restricted to interfaces assigned to the VRF and will use sockets bound
647
	to the VRF. Appropriate VRF interface must exist on OS level. For kernel
648
	protocol, an appropriate table still must be explicitly selected by
649
	<cf/table/ option. Note that the VRF support in BIRD and Linux kernel
650
	(4.11) is still in development and is currently problematic outside of
651
	multihop BGP.
652

    
653
	<tag><label id="proto-channel"><m/channel name/ [{<m/channel config/}]</tag>
654
	Every channel must be explicitly stated. See the protocol-specific
655
	configuration for the list of supported channel names. See the
656
	<ref id="channel-opts" name="channel configuration section"> for channel
657
	definition.
658
</descrip>
659

    
660
<p>There are several options that give sense only with certain protocols:
661

    
662
<descrip>
663
	<tag><label id="proto-iface">interface [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../] [ { <m/option/; [<m/.../] } ]</tag>
664
	Specifies a set of interfaces on which the protocol is activated with
665
	given interface-specific options. A set of interfaces specified by one
666
	interface option is described using an interface pattern. The interface
667
	pattern consists of a sequence of clauses (separated by commas), each
668
	clause is a mask specified as a shell-like pattern. Interfaces are
669
	matched by their name.
670

    
671
	An interface matches the pattern if it matches any of its clauses. If
672
	the clause begins with <cf/-/, matching interfaces are excluded. Patterns
673
	are processed left-to-right, thus <cf/interface "eth0", -"eth*", "*";/
674
	means eth0 and all non-ethernets.
675

    
676
	Some protocols (namely OSPFv2 and Direct) support extended clauses that
677
	may contain a mask, a prefix, or both of them. An interface matches such
678
	clause if its name matches the mask (if specified) and its address
679
	matches the prefix (if specified). Extended clauses are used when the
680
	protocol handles multiple addresses on an interface independently.
681

    
682
	An interface option can be used more times with different interface-specific
683
	options, in that case for given interface the first matching interface
684
	option is used.
685

    
686
	This option is allowed in Babel, BFD, Device, Direct, OSPF, RAdv and RIP
687
	protocols. In OSPF protocol it is used in the <cf/area/ subsection.
688

    
689
	Default: none.
690

    
691
	Examples:
692

    
693
	<cf>interface "*" { type broadcast; };</cf> - start the protocol on all
694
	interfaces with <cf>type broadcast</cf> option.
695

    
696
	<cf>interface "eth1", "eth4", "eth5" { type ptp; };</cf> - start the
697
	protocol on enumerated interfaces with <cf>type ptp</cf> option.
698

    
699
	<cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
700
	on all interfaces that have address from 192.168.0.0/16, but not from
701
	192.168.1.0/24.
702

    
703
	<cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
704
	on all interfaces that have address from 192.168.0.0/16, but not from
705
	192.168.1.0/24.
706

    
707
	<cf>interface "eth*" 192.168.1.0/24;</cf> - start the protocol on all
708
	ethernet interfaces that have address from 192.168.1.0/24.
709

    
710
	<tag><label id="proto-tx-class">tx class|dscp <m/num/</tag>
711
	This option specifies the value of ToS/DS/Class field in IP headers of
712
	the outgoing protocol packets. This may affect how the protocol packets
713
	are processed by the network relative to the other network traffic. With
714
	<cf/class/ keyword, the value (0-255) is used for the whole ToS/Class
715
	octet (but two bits reserved for ECN are ignored). With	<cf/dscp/
716
	keyword, the value (0-63) is used just for the DS field in the octet.
717
	Default value is 0xc0 (DSCP 0x30 - CS6).
718

    
719
	<tag><label id="proto-tx-priority">tx priority <m/num/</tag>
720
	This option specifies the local packet priority. This may affect how the
721
	protocol packets are processed in the local TX queues. This option is
722
	Linux specific. Default value is 7 (highest priority, privileged traffic).
723

    
724
	<tag><label id="proto-pass">password "<m/password/" [ { <m>password options</m> } ]</tag>
725
	Specifies a password that can be used by the protocol as a shared secret
726
	key. Password option can be used more times to specify more passwords.
727
	If more passwords are specified, it is a protocol-dependent decision
728
	which one is really used. Specifying passwords does not mean that
729
	authentication is enabled, authentication can be enabled by separate,
730
	protocol-dependent <cf/authentication/ option.
731

    
732
	This option is allowed in BFD, OSPF and RIP protocols. BGP has also
733
	<cf/password/ option, but it is slightly different and described
734
	separately.
735
	Default: none.
736
</descrip>
737

    
738
<p>Password option can contain section with some (not necessary all) password sub-options:
739

    
740
<descrip>
741
	<tag><label id="proto-pass-id">id <M>num</M></tag>
742
	ID of the password, (1-255). If it is not used, BIRD will choose ID based
743
	on an order of the password item in the interface. For example, second
744
	password item in one interface will have default ID 2. ID is used by
745
	some routing protocols to identify which password was used to
746
	authenticate protocol packets.
747

    
748
	<tag><label id="proto-pass-gen-from">generate from "<m/time/"</tag>
749
	The start time of the usage of the password for packet signing.
750
	The format of <cf><m/time/</cf> is <tt>dd-mm-yyyy HH:MM:SS</tt>.
751

    
752
	<tag><label id="proto-pass-gen-to">generate to "<m/time/"</tag>
753
	The last time of the usage of the password for packet signing.
754

    
755
	<tag><label id="proto-pass-accept-from">accept from "<m/time/"</tag>
756
	The start time of the usage of the password for packet verification.
757

    
758
	<tag><label id="proto-pass-accept-to">accept to "<m/time/"</tag>
759
	The last time of the usage of the password for packet verification.
760

    
761
	<tag><label id="proto-pass-from">from "<m/time/"</tag>
762
	Shorthand for setting both <cf/generate from/ and <cf/accept from/.
763

    
764
	<tag><label id="proto-pass-to">to "<m/time/"</tag>
765
	Shorthand for setting both <cf/generate to/ and <cf/accept to/.
766

    
767
	<tag><label id="proto-pass-algorithm">algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 )</tag>
768
	The message authentication algorithm for the password when cryptographic
769
	authentication is enabled. The default value depends on the protocol.
770
	For RIP and OSPFv2 it is Keyed-MD5 (for compatibility), for OSPFv3
771
	protocol it is HMAC-SHA-256.
772

    
773
</descrip>
774

    
775

    
776
<sect>Channel options
777
<label id="channel-opts">
778

    
779
<p>Every channel belongs to a protocol and is configured inside its block. The
780
minimal channel config is empty, then it uses default values. The name of the
781
channel implies its nettype. Channel definitions can be inherited from protocol
782
templates. Multiple definitions of the same channel are forbidden, but channels
783
inherited from templates can be updated by new definitions.
784

    
785
<descrip>
786
	<tag><label id="proto-table">table <m/name/</tag>
787
	Specify a table to which the channel is connected. Default: the first
788
	table of given nettype.
789

    
790
	<tag><label id="proto-preference">preference <m/expr/</tag>
791
	Sets the preference of routes generated by the protocol and imported
792
	through this channel. Default: protocol dependent.
793

    
794
	<tag><label id="proto-import">import all | none | filter <m/name/ | filter { <m/filter commands/ } | where <m/boolean filter expression/</tag>
795
	Specify a filter to be used for filtering routes coming from the
796
	protocol to the routing table. <cf/all/ is for keeping all routes,
797
	<cf/none/ is for dropping all routes. Default: <cf/all/ (except for
798
	EBGP).
799

    
800
	<tag><label id="proto-export">export <m/filter/</tag>
801
	This is similar to the <cf>import</cf> keyword, except that it works in
802
	the direction from the routing table to the protocol. Default: <cf/none/
803
	(except for EBGP).
804

    
805
	<tag><label id="proto-import-keep-filtered">import keep filtered <m/switch/</tag>
806
	Usually, if an import filter rejects a route, the route is forgotten.
807
	When this option is active, these routes are kept in the routing table,
808
	but they are hidden and not propagated to other protocols. But it is
809
	possible to show them using <cf/show route filtered/. Note that this
810
	option does not work for the pipe protocol. Default: off.
811

    
812
	<tag><label id="proto-import-limit">import limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
813
	Specify an import route limit (a maximum number of routes imported from
814
	the protocol) and optionally the action to be taken when the limit is
815
	hit. Warn action just prints warning log message. Block action discards
816
	new routes coming from the protocol. Restart and disable actions shut
817
	the protocol down like appropriate commands. Disable is the default
818
	action if an action is not explicitly specified. Note that limits are
819
	reset during protocol reconfigure, reload or restart. Default: <cf/off/.
820

    
821
	<tag><label id="proto-receive-limit">receive limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
822
	Specify an receive route limit (a maximum number of routes received from
823
	the protocol and remembered). It works almost identically to <cf>import
824
	limit</cf> option, the only difference is that if <cf/import keep
825
	filtered/ option is active, filtered routes are counted towards the
826
	limit and blocked routes are forgotten, as the main purpose of the
827
	receive limit is to protect routing tables from overflow. Import limit,
828
	on the contrary, counts accepted routes only and routes blocked by the
829
	limit are handled like filtered routes. Default: <cf/off/.
830

    
831
	<tag><label id="proto-export-limit">export limit [ <m/number/ | off ] [action warn | block | restart | disable]</tag>
832
	Specify an export route limit, works similarly to the <cf>import
833
	limit</cf> option, but for the routes exported to the protocol. This
834
	option is experimental, there are some problems in details of its
835
	behavior -- the number of exported routes can temporarily exceed the
836
	limit without triggering it during protocol reload, exported routes
837
	counter ignores route blocking and block action also blocks route
838
	updates of already accepted routes -- and these details will probably
839
	change in the future. Default: <cf/off/.
840
</descrip>
841

    
842
<p>This is a trivial example of RIP configured for IPv6 on all interfaces:
843
<code>
844
protocol rip ng {
845
	ipv6;
846
	interface "*";
847
}
848
</code>
849

    
850
<p>This is a non-trivial example.
851
<code>
852
protocol rip ng {
853
	ipv6 {
854
		table mytable6;
855
		import filter { ... };
856
		export filter { ... };
857
		import limit 50;
858
	};
859
	interface "*";
860
}
861
</code>
862

    
863
<p>And this is even more complicated example using templates.
864
<code>
865
template bgp {
866
	local 198.51.100.14 as 65000;
867

    
868
	ipv4 {
869
		table mytable4;
870
		import filter { ... };
871
		export none;
872
	};
873
	ipv6 {
874
		table mytable6;
875
		import filter { ... };
876
		export none;
877
	};
878
}
879

    
880
protocol bgp from  {
881
	neighbor 198.51.100.130 as 64496;
882

    
883
	# IPv4 channel is inherited as-is, while IPv6
884
	# channel is adjusted by export filter option
885
	ipv6 {
886
		export filter { ... };
887
	};
888
}
889
</code>
890

    
891

    
892
<chapt>Remote control
893
<label id="remote-control">
894

    
895
<p>You can use the command-line client <file>birdc</file> to talk with a running
896
BIRD. Communication is done using a <file/bird.ctl/ UNIX domain socket (unless
897
changed with the <tt/-s/ option given to both the server and the client). The
898
commands can perform simple actions such as enabling/disabling of protocols,
899
telling BIRD to show various information, telling it to show routing table
900
filtered by filter, or asking BIRD to reconfigure. Press <tt/?/ at any time to
901
get online help. Option <tt/-r/ can be used to enable a restricted mode of BIRD
902
client, which allows just read-only commands (<cf/show .../). Option <tt/-v/ can
903
be passed to the client, to make it dump numeric return codes along with the
904
messages. You do not necessarily need to use <file/birdc/ to talk to BIRD, your
905
own applications could do that, too -- the format of communication between BIRD
906
and <file/birdc/ is stable (see the programmer's documentation).
907

    
908
<p>There is also lightweight variant of BIRD client called <file/birdcl/, which
909
does not support command line editing and history and has minimal dependencies.
910
This is useful for running BIRD in resource constrained environments, where
911
Readline library (required for regular BIRD client) is not available.
912

    
913
<p>Many commands have the <m/name/ of the protocol instance as an argument.
914
This argument can be omitted if there exists only a single instance.
915

    
916
<p>Here is a brief list of supported functions:
917

    
918
<descrip>
919
	<tag><label id="cli-show-status">show status</tag>
920
	Show router status, that is BIRD version, uptime and time from last
921
	reconfiguration.
922

    
923
	<tag><label id="cli-show-interfaces">show interfaces [summary]</tag>
924
	Show the list of interfaces. For each interface, print its type, state,
925
	MTU and addresses assigned.
926

    
927
	<tag><label id="cli-show-protocols">show protocols [all]</tag>
928
	Show list of protocol instances along with tables they are connected to
929
	and protocol status, possibly giving verbose information, if <cf/all/ is
930
	specified.
931

    
932
	<!-- TODO: Move these protocol-specific remote control commands to the protocol sections -->
933
	<tag><label id="cli-show-ospf-iface">show ospf interface [<m/name/] ["<m/interface/"]</tag>
934
	Show detailed information about OSPF interfaces.
935

    
936
	<tag><label id="cli-show-ospf-neighbors">show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
937
	Show a list of OSPF neighbors and a state of adjacency to them.
938

    
939
	<tag><label id="cli-show-ospf-state">show ospf state [all] [<m/name/]</tag>
940
	Show detailed information about OSPF areas based on a content of the
941
	link-state database. It shows network topology, stub networks,
942
	aggregated networks and routers from other areas and external routes.
943
	The command shows information about reachable network nodes, use option
944
	<cf/all/ to show information about all network nodes in the link-state
945
	database.
946

    
947
	<tag><label id="cli-show-ospf-topology">show ospf topology [all] [<m/name/]</tag>
948
	Show a topology of OSPF areas based on a content of the link-state
949
	database. It is just a stripped-down version of 'show ospf state'.
950

    
951
	<tag><label id="cli-show-ospf-lsadb">show ospf lsadb [global | area <m/id/ | link] [type <m/num/] [lsid <m/id/] [self | router <m/id/] [<m/name/] </tag>
952
	Show contents of an OSPF LSA database. Options could be used to filter
953
	entries.
954

    
955
	<tag><label id="cli-show-rip-interfaces">show rip interfaces [<m/name/] ["<m/interface/"]</tag>
956
	Show detailed information about RIP interfaces.
957

    
958
	<tag><label id="cli-show-rip-neighbors">show rip neighbors [<m/name/] ["<m/interface/"]</tag>
959
	Show a list of RIP neighbors and associated state.
960

    
961
	<tag><label id="cli-show-static">show static [<m/name/]</tag>
962
	Show detailed information about static routes.
963

    
964
	<tag><label id="cli-show-bfd-sessions">show bfd sessions [<m/name/]</tag>
965
	Show information about BFD sessions.
966

    
967
	<tag><label id="cli-show-symbols">show symbols [table|filter|function|protocol|template|roa|<m/symbol/]</tag>
968
	Show the list of symbols defined in the configuration (names of
969
	protocols, routing tables etc.).
970

    
971
	<tag><label id="cli-show-route">show route [[for] <m/prefix/|<m/IP/] [table (<m/t/ | all)] [filter <m/f/|where <m/c/] [(export|preexport|noexport) <m/p/] [protocol <m/p/] [(stats|count)] [<m/options/]</tag>
972
	Show contents of specified routing tables, that is routes, their metrics
973
	and (in case the <cf/all/ switch is given) all their attributes.
974

    
975
	<p>You can specify a <m/prefix/ if you want to print routes for a
976
	specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
977
	the entry which will be used for forwarding of packets to the given
978
	destination. By default, all routes for each network are printed with
979
	the selected one at the top, unless <cf/primary/ is given in which case
980
	only the selected route is shown.
981

    
982
	<p>The <cf/show route/ command can process one or multiple routing
983
	tables. The set of selected tables is determined on three levels: First,
984
	tables can be explicitly selected by <cf/table/ switch, which could be
985
	used multiple times, all tables are specified by <cf/table all/. Second,
986
	tables can be implicitly selected by channels or protocols that are
987
	arguments of several other switches (e.g., <cf/export/, <cf/protocol/).
988
	Last, the set of default tables is used: <cf/master4/, <cf/master6/ and
989
	each first table of any other network type.
990

    
991
	<p>You can also ask for printing only routes processed and accepted by
992
	a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
993
	</cf> or matching a given condition (<cf>where <m/condition/</cf>).
994

    
995
	The <cf/export/, <cf/preexport/ and <cf/noexport/ switches ask for
996
	printing of routes that are exported to the specified protocol or
997
	channel. With <cf/preexport/, the export filter of the channel is
998
	skipped. With <cf/noexport/, routes rejected by the export filter are
999
	printed instead. Note that routes not exported for other reasons
1000
	(e.g. secondary routes or routes imported from that protocol) are not
1001
	printed even with <cf/noexport/. These switches also imply that
1002
	associated routing tables are selected instead of default ones.
1003

    
1004
	<p>You can also select just routes added by a specific protocol.
1005
	<cf>protocol <m/p/</cf>. This switch also implies that associated
1006
	routing tables are selected instead of default ones.
1007

    
1008
	<p>If BIRD is configured to keep filtered routes (see <cf/import keep
1009
	filtered/ option), you can show them instead of routes by using
1010
	<cf/filtered/ switch.
1011

    
1012
	<p>The <cf/stats/ switch requests showing of route statistics (the
1013
	number of networks, number of routes before and after filtering). If
1014
	you use <cf/count/ instead, only the statistics will be printed.
1015

    
1016
	<tag><label id="cli-configure">configure [soft] ["<m/config file/"] [timeout [<m/num/]]</tag>
1017
	Reload configuration from a given file. BIRD will smoothly switch itself
1018
	to the new configuration, protocols are reconfigured if possible,
1019
	restarted otherwise. Changes in filters usually lead to restart of
1020
	affected protocols.
1021

    
1022
	If <cf/soft/ option is used, changes in filters does not cause BIRD to
1023
	restart affected protocols, therefore already accepted routes (according
1024
	to old filters) would be still propagated, but new routes would be
1025
	processed according to the new filters.
1026

    
1027
	If <cf/timeout/ option is used, config timer is activated. The new
1028
	configuration could be either confirmed using <cf/configure confirm/
1029
	command, or it will be reverted to the old one when the config timer
1030
	expires. This is useful for cases when reconfiguration breaks current
1031
	routing and a router becomes inaccessible for an administrator. The
1032
	config timeout expiration is equivalent to <cf/configure undo/
1033
	command. The timeout duration could be specified, default is 300 s.
1034

    
1035
	<tag><label id="cli-configure-confirm">configure confirm</tag>
1036
	Deactivate the config undo timer and therefore confirm the current
1037
	configuration.
1038

    
1039
	<tag><label id="cli-configure-undo">configure undo</tag>
1040
	Undo the last configuration change and smoothly switch back to the
1041
	previous (stored) configuration. If the last configuration change was
1042
	soft, the undo change is also soft. There is only one level of undo, but
1043
	in some specific cases when several reconfiguration requests are given
1044
	immediately in a row and the intermediate ones are skipped then the undo
1045
	also skips them back.
1046

    
1047
	<tag><label id="cli-configure-check">configure check ["<m/config file/"]</tag>
1048
	Read and parse given config file, but do not use it. useful for checking
1049
	syntactic and some semantic validity of an config file.
1050

    
1051
	<tag><label id="cli-enable-disable-restart">enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
1052
	Enable, disable or restart a given protocol instance, instances matching
1053
	the <cf><m/pattern/</cf> or <cf/all/ instances.
1054

    
1055
	<tag><label id="cli-reload">reload [in|out] <m/name/|"<m/pattern/"|all</tag>
1056
	Reload a given protocol instance, that means re-import routes from the
1057
	protocol instance and re-export preferred routes to the instance. If
1058
	<cf/in/ or <cf/out/ options are used, the command is restricted to one
1059
	direction (re-import or re-export).
1060

    
1061
	This command is useful if appropriate filters have changed but the
1062
	protocol instance was not restarted (or reloaded), therefore it still
1063
	propagates the old set of routes. For example when <cf/configure soft/
1064
	command was used to change filters.
1065

    
1066
	Re-export always succeeds, but re-import is protocol-dependent and might
1067
	fail (for example, if BGP neighbor does not support route-refresh
1068
	extension). In that case, re-export is also skipped. Note that for the
1069
	pipe protocol, both directions are always reloaded together (<cf/in/ or
1070
	<cf/out/ options are ignored in that case).
1071

    
1072
	<tag><label id="cli-down">down</tag>
1073
	Shut BIRD down.
1074

    
1075
	<tag><label id="cli-debug">debug <m/protocol/|<m/pattern/|all all|off|{ states|routes|filters|events|packets [, <m/.../] }</tag>
1076
	Control protocol debugging.
1077

    
1078
	<tag><label id="cli-dump">dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
1079
	Dump contents of internal data structures to the debugging output.
1080

    
1081
	<tag><label id="cli-echo">echo all|off|{ <m/list of log classes/ } [ <m/buffer-size/ ]</tag>
1082
	Control echoing of log messages to the command-line output.
1083
	See <ref id="opt-log" name="log option"> for a list of log classes.
1084

    
1085
	<tag><label id="cli-eval">eval <m/expr/</tag>
1086
	Evaluate given expression.
1087
</descrip>
1088

    
1089

    
1090
<chapt>Filters
1091
<label id="filters">
1092

    
1093
<sect>Introduction
1094
<label id="filters-intro">
1095

    
1096
<p>BIRD contains a simple programming language. (No, it can't yet read mail :-).
1097
There are two objects in this language: filters and functions. Filters are
1098
interpreted by BIRD core when a route is being passed between protocols and
1099
routing tables. The filter language contains control structures such as if's and
1100
switches, but it allows no loops. An example of a filter using many features can
1101
be found in <file>filter/test.conf</file>.
1102

    
1103
<p>Filter gets the route, looks at its attributes and modifies some of them if
1104
it wishes. At the end, it decides whether to pass the changed route through
1105
(using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks like
1106
this:
1107

    
1108
<code>
1109
filter not_too_far
1110
int var;
1111
{
1112
	if defined( rip_metric ) then
1113
		var = rip_metric;
1114
	else {
1115
		var = 1;
1116
		rip_metric = 1;
1117
	}
1118
	if rip_metric &gt; 10 then
1119
		reject "RIP metric is too big";
1120
	else
1121
		accept "ok";
1122
}
1123
</code>
1124

    
1125
<p>As you can see, a filter has a header, a list of local variables, and a body.
1126
The header consists of the <cf/filter/ keyword followed by a (unique) name of
1127
filter. The list of local variables consists of <cf><M>type name</M>;</cf>
1128
pairs where each pair defines one local variable. The body consists of <cf>
1129
{ <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You
1130
can group several statements to a single compound statement by using braces
1131
(<cf>{ <M>statements</M> }</cf>) which is useful if you want to make a bigger
1132
block of code conditional.
1133

    
1134
<p>BIRD supports functions, so that you don't have to repeat the same blocks of
1135
code over and over. Functions can have zero or more parameters and they can have
1136
local variables. Recursion is not allowed. Function definitions look like this:
1137

    
1138
<code>
1139
function name ()
1140
int local_variable;
1141
{
1142
	local_variable = 5;
1143
}
1144

    
1145
function with_parameters (int parameter)
1146
{
1147
	print parameter;
1148
}
1149
</code>
1150

    
1151
<p>Unlike in C, variables are declared after the <cf/function/ line, but before
1152
the first <cf/{/. You can't declare variables in nested blocks. Functions are
1153
called like in C: <cf>name(); with_parameters(5);</cf>. Function may return
1154
values using the <cf>return <m/[expr]/</cf> command. Returning a value exits
1155
from current function (this is similar to C).
1156

    
1157
<p>Filters are declared in a way similar to functions except they can't have
1158
explicit parameters. They get a route table entry as an implicit parameter, it
1159
is also passed automatically to any functions called. The filter must terminate
1160
with either <cf/accept/ or <cf/reject/ statement. If there's a runtime error in
1161
filter, the route is rejected.
1162

    
1163
<p>A nice trick to debug filters is to use <cf>show route filter <m/name/</cf>
1164
from the command line client. An example session might look like:
1165

    
1166
<code>
1167
pavel@bug:~/bird$ ./birdc -s bird.ctl
1168
BIRD 0.0.0 ready.
1169
bird> show route
1170
10.0.0.0/8         dev eth0 [direct1 23:21] (240)
1171
195.113.30.2/32    dev tunl1 [direct1 23:21] (240)
1172
127.0.0.0/8        dev lo [direct1 23:21] (240)
1173
bird> show route ?
1174
show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
1175
bird> show route filter { if 127.0.0.5 &tilde; net then accept; }
1176
127.0.0.0/8        dev lo [direct1 23:21] (240)
1177
bird>
1178
</code>
1179

    
1180

    
1181
<sect>Data types
1182
<label id="data-types">
1183

    
1184
<p>Each variable and each value has certain type. Booleans, integers and enums
1185
are incompatible with each other (that is to prevent you from shooting in the
1186
foot).
1187

    
1188
<descrip>
1189
	<tag><label id="type-bool">bool</tag>
1190
	This is a boolean type, it can have only two values, <cf/true/ and
1191
	<cf/false/. Boolean is the only type you can use in <cf/if/ statements.
1192

    
1193
	<tag><label id="type-int">int</tag>
1194
	This is a general integer type. It is an unsigned 32bit type; i.e., you
1195
	can expect it to store values from 0 to 4294967295. Overflows are not
1196
	checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
1197

    
1198
	<tag><label id="type-pair">pair</tag>
1199
	This is a pair of two short integers. Each component can have values
1200
	from 0 to 65535. Literals of this type are written as <cf/(1234,5678)/.
1201
	The same syntax can also be used to construct a pair from two arbitrary
1202
	integer expressions (for example <cf/(1+2,a)/).
1203

    
1204
	<tag><label id="type-quad">quad</tag>
1205
	This is a dotted quad of numbers used to represent router IDs (and
1206
	others). Each component can have a value from 0 to 255. Literals of
1207
	this type are written like IPv4 addresses.
1208

    
1209
	<tag><label id="type-string">string</tag>
1210
	This is a string of characters. There are no ways to modify strings in
1211
	filters. You can pass them between functions, assign them to variables
1212
	of type <cf/string/, print such variables, use standard string
1213
	comparison operations (e.g. <cf/=, !=, &lt;, &gt;, &lt;=, &gt;=/), but
1214
	you can't concatenate two strings. String literals are written as
1215
	<cf/"This is a string constant"/. Additionally matching (<cf/&tilde;,
1216
	!&tilde;/) operators could be used to match a string value against
1217
	a shell pattern (represented also as a string).
1218

    
1219
	<tag><label id="type-ip">ip</tag>
1220
	This type can hold a single IP address. The IPv4 addresses are stored as
1221
	IPv4-Mapped IPv6 addresses so one data type for both of them is used.
1222
	Whether the address is IPv4 or not may be checked by <cf>.is_ip4</cf>
1223
	which returns <cf/bool/. IP addresses are written in the standard
1224
	notation (<cf/10.20.30.40/ or <cf/fec0:3:4::1/). You can apply special
1225
	operator <cf>.mask(<M>num</M>)</cf> on values of type ip. It masks out
1226
	all but first <cf><M>num</M></cf> bits from the IP address. So
1227
	<cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
1228

    
1229
	<tag><label id="type-prefix">prefix</tag>
1230
	This type can hold a network prefix consisting of IP address, prefix
1231
	length and several other values. This is the key in route tables.
1232

    
1233
	Prefixes may be of several types, which can be determined by the special
1234
	operator <cf/.type/. The type may be:
1235

    
1236
	<cf/NET_IP4/ and <cf/NET_IP6/ prefixes hold an IP prefix. The literals
1237
	are written as <cf><m/ipaddress//<m/pxlen/</cf>,
1238
	or <cf><m>ipaddress</m>/<m>netmask</m></cf>. There are two special
1239
	operators on these: <cf/.ip/ which extracts the IP address from the
1240
	pair, and <cf/.len/, which separates prefix length from the pair.
1241
	So <cf>1.2.0.0/16.len = 16</cf> is true.
1242

    
1243
	<cf/NET_VPN4/ and <cf/NET_VPN6/ prefixes hold an IP prefix with VPN
1244
	Route Distinguisher (<rfc id="4364">). They support the same special
1245
	operators as IP prefixes, and also <cf/.rd/ which extracts the Route
1246
	Distinguisher. Their literals are written
1247
	as <cf><m/vpnrd/ <m/ipprefix/</cf>
1248

    
1249
	<cf/NET_ROA4/ and <cf/NET_ROA6/ prefixes hold an IP prefix range
1250
	together with an ASN. They support the same special operators as IP
1251
	prefixes, and also <cf/.maxlen/ which extracts maximal prefix length,
1252
	and <cf/.asn/ which extracts the ASN.
1253

    
1254
	<cf/NET_FLOW4/ and <cf/NET_FLOW6/ hold an IP prefix together with a
1255
	flowspec rule. Filters currently don't support flowspec parsing.
1256

    
1257
	<cf/NET_MPLS/ holds a single MPLS label and its handling is currently
1258
	not implemented.
1259

    
1260
	<tag><label id="type-vpnrd">vpnrd</tag>
1261
	This is a route distinguisher according to <rfc id="4364">. There are
1262
	three kinds of RD's: <cf><m/asn/:<m/32bit int/</cf>, <cf><m/asn4/:<m/16bit int/</cf>
1263
	and <cf><m/IPv4 address/:<m/32bit int/</cf>
1264

    
1265
	<tag><label id="type-ec">ec</tag>
1266
	This is a specialized type used to represent BGP extended community
1267
	values. It is essentially a 64bit value, literals of this type are
1268
	usually written as <cf>(<m/kind/, <m/key/, <m/value/)</cf>, where
1269
	<cf/kind/ is a kind of extended community (e.g. <cf/rt/ / <cf/ro/ for a
1270
	route target / route origin communities), the format and possible values
1271
	of <cf/key/ and <cf/value/ are usually integers, but it depends on the
1272
	used kind. Similarly to pairs, ECs can be constructed using expressions
1273
	for <cf/key/ and <cf/value/ parts, (e.g. <cf/(ro, myas, 3*10)/, where
1274
	<cf/myas/ is an integer variable).
1275

    
1276
	<tag><label id="type-lc">lc</tag>
1277
	This is a specialized type used to represent BGP large community
1278
	values. It is essentially a triplet of 32bit values, where the first
1279
	value is reserved for the AS number of the issuer, while meaning of
1280
	remaining parts is defined by the issuer. Literals of this type are
1281
	written as <cf/(123, 456, 789)/, with any integer values. Similarly to
1282
	pairs, LCs can be constructed using expressions for its parts, (e.g.
1283
	<cf/(myas, 10+20, 3*10)/, where <cf/myas/ is an integer variable).
1284

    
1285
	<tag><label id="type-set">int|pair|quad|ip|prefix|ec|lc|enum set</tag>
1286
	Filters recognize four types of sets. Sets are similar to strings: you
1287
	can pass them around but you can't modify them. Literals of type <cf>int
1288
	set</cf> look like <cf> [ 1, 2, 5..7 ]</cf>. As you can see, both simple
1289
	values and ranges are permitted in sets.
1290

    
1291
	For pair sets, expressions like <cf/(123,*)/ can be used to denote
1292
	ranges (in that case <cf/(123,0)..(123,65535)/). You can also use
1293
	<cf/(123,5..100)/ for range <cf/(123,5)..(123,100)/. You can also use
1294
	<cf/*/ and <cf/a..b/ expressions in the first part of a pair, note that
1295
	such expressions are translated to a set of intervals, which may be
1296
	memory intensive. E.g. <cf/(*,4..20)/ is translated to <cf/(0,4..20),
1297
	(1,4..20), (2,4..20), ... (65535, 4..20)/.
1298

    
1299
	EC sets use similar expressions like pair sets, e.g. <cf/(rt, 123,
1300
	10..20)/ or <cf/(ro, 123, *)/. Expressions requiring the translation
1301
	(like <cf/(rt, *, 3)/) are not allowed (as they usually have 4B range
1302
	for ASNs).
1303

    
1304
	Also LC sets use similar expressions like pair sets. You can use ranges
1305
	and wildcards, but if one field uses that, more specific (later) fields
1306
	must be wildcards. E.g., <cf/(10, 20..30, *)/ or <cf/(10, 20, 30..40)/
1307
	is valid, while <cf/(10, *, 20..30)/ or <cf/(10, 20..30, 40)/ is not
1308
	valid.
1309

    
1310
	You can also use expressions for int, pair, EC and LC set values.
1311
	However, it must be possible to evaluate these expressions before daemon
1312
	boots. So you can use only constants inside them. E.g.
1313

    
1314
	<code>
1315
	 define one=1;
1316
	 define myas=64500;
1317
	 int set odds;
1318
	 pair set ps;
1319
	 ec set es;
1320

    
1321
	 odds = [ one, 2+1, 6-one, 2*2*2-1, 9, 11 ];
1322
	 ps = [ (1,one+one), (3,4)..(4,8), (5,*), (6,3..6), (7..9,*) ];
1323
	 es = [ (rt, myas, 3*10), (rt, myas+one, 0..16*16*16-1), (ro, myas+2, *) ];
1324
	</code>
1325

    
1326
	Sets of prefixes are special: their literals does not allow ranges, but
1327
	allows prefix patterns that are written
1328
	as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
1329
	Prefix <cf><m>ip1</m>/<m>len1</m></cf> matches prefix
1330
	pattern <cf><m>ip2</m>/<m>len2</m>{<m>l</m>,<m>h</m>}</cf> if the
1331
	first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are
1332
	identical and <cf>len1 &lt;= ip1 &lt;= len2</cf>. A valid prefix pattern
1333
	has to satisfy <cf>low &lt;= high</cf>, but <cf/pxlen/ is not
1334
	constrained by <cf/low/ or <cf/high/. Obviously, a prefix matches a
1335
	prefix set literal if it matches any prefix pattern in the prefix set
1336
	literal.
1337

    
1338
	There are also two shorthands for prefix patterns: <cf><m/address//<m/len/+</cf>
1339
	is a shorthand for <cf><m/address//<m/len/{<m/len/,<m/maxlen/}</cf>
1340
	(where <cf><m/maxlen/</cf> is 32 for IPv4 and 128 for IPv6), that means
1341
	network prefix <cf><m/address//<m/len/</cf> and all its	subnets.
1342
	<cf><m/address//<m/len/-</cf> is a shorthand for
1343
	<cf><m/address//<m/len/{0,<m/len/}</cf>, that means network prefix
1344
	<cf><m/address//<m/len/</cf> and all its supernets (network prefixes
1345
	that contain it).
1346

    
1347
	For example, <cf>[ 1.0.0.0/8, 2.0.0.0/8+, 3.0.0.0/8-, 4.0.0.0/8{16,24}
1348
	]</cf> matches prefix <cf>1.0.0.0/8</cf>, all subprefixes of
1349
	<cf>2.0.0.0/8</cf>, all superprefixes of <cf>3.0.0.0/8</cf> and prefixes
1350
	<cf/4.X.X.X/ whose prefix length is 16 to 24. <cf>[ 0.0.0.0/0{20,24} ]</cf>
1351
	matches all prefixes (regardless of IP address) whose prefix length is
1352
	20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP
1353
	address <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 &tilde; [ 1.0.0.0/8{15,17} ]</cf>
1354
	is true, but <cf>1.0.0.0/16 &tilde; [ 1.0.0.0/8- ]</cf> is false.
1355

    
1356
	Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
1357
	in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as
1358
	<cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
1359
	<cf>192.168.0.0/16{24,32}</cf>.
1360

    
1361
	It is possible to mix IPv4 and IPv6 prefixes/addresses in a prefix/ip set
1362
	but its behavior may change between versions without any warning; don't do
1363
	it unless you are more than sure what you are doing. (Really, don't do it.)
1364

    
1365
	<tag><label id="type-enum">enum</tag>
1366
	Enumeration types are fixed sets of possibilities. You can't define your
1367
	own variables of such type, but some route attributes are of enumeration
1368
	type. Enumeration types are incompatible with each other.
1369

    
1370
	<tag><label id="type-bgppath">bgppath</tag>
1371
	BGP path is a list of autonomous system numbers. You can't write
1372
	literals of this type. There are several special operators on bgppaths:
1373

    
1374
	<cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
1375

    
1376
	<cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
1377

    
1378
	<cf><m/P/.last_nonaggregated</cf> returns the last ASN in the non-aggregated part of the path <m/P/.
1379

    
1380
	Both <cf/first/ and <cf/last/ return zero if there is no appropriate
1381
	ASN, for example if the path contains an AS set element as the first (or
1382
	the last) part. If the path ends with an AS set, <cf/last_nonaggregated/
1383
	may be used to get last ASN before any AS set.
1384

    
1385
	<cf><m/P/.len</cf> returns the length of path <m/P/.
1386

    
1387
	<cf><m/P/.empty</cf> makes the path <m/P/ empty.
1388

    
1389
	<cf>prepend(<m/P/,<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and
1390
	returns the result.
1391

    
1392
	<cf>delete(<m/P/,<m/A/)</cf> deletes all instances of ASN <m/A/ from
1393
	from path <m/P/ and returns the result. <m/A/ may also be an integer
1394
	set, in that case the operator deletes all ASNs from path <m/P/ that are
1395
	also members of set <m/A/.
1396

    
1397
	<cf>filter(<m/P/,<m/A/)</cf> deletes all ASNs from path <m/P/ that are
1398
	not members of integer set <m/A/. I.e., <cf/filter/ do the same as
1399
	<cf/delete/ with inverted set <m/A/.
1400

    
1401
	Statement <cf><m/P/ = prepend(<m/P/, <m/A/);</cf> can be shortened to
1402
	<cf><m/P/.prepend(<m/A/);</cf> if <m/P/ is appropriate route attribute
1403
	(for example <cf/bgp_path/). Similarly for <cf/delete/ and <cf/filter/.
1404

    
1405
	<tag><label id="type-bgpmask">bgpmask</tag>
1406
	BGP masks are patterns used for BGP path matching (using <cf>path
1407
	&tilde; [= 2 3 5 * =]</cf> syntax). The masks resemble wildcard patterns
1408
	as used by UNIX shells. Autonomous system numbers match themselves,
1409
	<cf/*/ matches any (even empty) sequence of arbitrary AS numbers and
1410
	<cf/?/ matches one arbitrary AS number. For example, if <cf>bgp_path</cf>
1411
 	is 4 3 2 1, then: <tt>bgp_path &tilde; [= * 4 3 * =]</tt> is true,
1412
	but <tt>bgp_path &tilde; [= * 4 5 * =]</tt> is false. BGP mask
1413
	expressions can also contain integer expressions enclosed in parenthesis
1414
	and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>. You can
1415
        also use ranges, for example <tt>[= * 3..5 2 100..200 * =]</tt>.
1416

    
1417
	<tag><label id="type-clist">clist</tag>
1418
	Clist is similar to a set, except that unlike other sets, it can be
1419
	modified. The type is used for community list (a set of pairs) and for
1420
	cluster list (a set of quads). There exist no literals of this type.
1421
	There are three special operators on clists:
1422

    
1423
	<cf><m/C/.len</cf> returns the length of clist <m/C/.
1424

    
1425
	<cf><m/C/.empty</cf> makes the list <m/C/ empty.
1426

    
1427
	<cf>add(<m/C/,<m/P/)</cf> adds pair (or quad) <m/P/ to clist <m/C/ and
1428
	returns the result. If item <m/P/ is already in clist <m/C/, it does
1429
	nothing. <m/P/ may also be a clist, in that case all its members are
1430
	added; i.e., it works as clist union.
1431

    
1432
	<cf>delete(<m/C/,<m/P/)</cf> deletes pair (or quad) <m/P/ from clist
1433
	<m/C/ and returns the result. If clist <m/C/ does not contain item
1434
	<m/P/, it does nothing. <m/P/ may also be a pair (or quad) set, in that
1435
	case the operator deletes all items from clist <m/C/ that are also
1436
	members of set <m/P/. Moreover, <m/P/ may also be a clist, which works
1437
	analogously; i.e., it works as clist difference.
1438

    
1439
	<cf>filter(<m/C/,<m/P/)</cf> deletes all items from clist <m/C/ that are
1440
	not members of pair (or quad) set <m/P/. I.e., <cf/filter/ do the same
1441
	as <cf/delete/ with inverted set <m/P/. <m/P/ may also be a clist, which
1442
	works analogously; i.e., it works as clist intersection.
1443

    
1444
	Statement <cf><m/C/ = add(<m/C/, <m/P/);</cf> can be shortened to
1445
	<cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route attribute (for
1446
	example <cf/bgp_community/). Similarly for <cf/delete/ and <cf/filter/.
1447

    
1448
	<tag><label id="type-eclist">eclist</tag>
1449
	Eclist is a data type used for BGP extended community lists. Eclists
1450
	are very similar to clists, but they are sets of ECs instead of pairs.
1451
	The same operations (like <cf/add/, <cf/delete/ or <cf/&tilde;/ and
1452
	<cf/!&tilde;/ membership operators) can be used to modify or test
1453
	eclists, with ECs instead of pairs as arguments.
1454

    
1455
	<tag><label id="type-lclist">lclist/</tag>
1456
	Lclist is a data type used for BGP large community lists. Like eclists,
1457
	lclists are very similar to clists, but they are sets of LCs instead of
1458
	pairs. The same operations (like <cf/add/, <cf/delete/ or <cf/&tilde;/
1459
	and <cf/!&tilde;/ membership operators) can be used to modify or test
1460
	lclists, with LCs instead of pairs as arguments.
1461
</descrip>
1462

    
1463
<sect>Operators
1464
<label id="operators">
1465

    
1466
<p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>,
1467
parentheses <cf/(a*(b+c))/, comparison <cf/(a=b, a!=b, a&lt;b, a&gt;=b)/.
1468
Logical operations include unary not (<cf/!/), and (<cf/&amp;&amp;/), and or
1469
(<cf/&verbar;&verbar;/). Special operators include (<cf/&tilde;/,
1470
<cf/!&tilde;/) for "is (not) element of a set" operation - it can be used on
1471
element and set of elements of the same type (returning true if element is
1472
contained in the given set), or on two strings (returning true if first string
1473
matches a shell-like pattern stored in second string) or on IP and prefix
1474
(returning true if IP is within the range defined by that prefix), or on prefix
1475
and prefix (returning true if first prefix is more specific than second one) or
1476
on bgppath and bgpmask (returning true if the path matches the mask) or on
1477
number and bgppath (returning true if the number is in the path) or on bgppath
1478
and int (number) set (returning true if any ASN from the path is in the set) or
1479
on pair/quad and clist (returning true if the pair/quad is element of the
1480
clist) or on clist and pair/quad set (returning true if there is an element of
1481
the clist that is also a member of the pair/quad set).
1482

    
1483
<p>There is one operator related to ROA infrastructure - <cf/roa_check()/. It
1484
examines a ROA table and does <rfc id="6483"> route origin validation for a
1485
given network prefix. The basic usage is <cf>roa_check(<m/table/)</cf>, which
1486
checks current route (which should be from BGP to have AS_PATH argument) in the
1487
specified ROA table and returns ROA_UNKNOWN if there is no relevant ROA,
1488
ROA_VALID if there is a matching ROA, or ROA_INVALID if there are some relevant
1489
ROAs but none of them match. There is also an extended variant
1490
<cf>roa_check(<m/table/, <m/prefix/, <m/asn/)</cf>, which allows to specify a
1491
prefix and an ASN as arguments.
1492

    
1493

    
1494
<sect>Control structures
1495
<label id="control-structures">
1496

    
1497
<p>Filters support two control structures: conditions and case switches.
1498

    
1499
<p>Syntax of a condition is: <cf>if <M>boolean expression</M> then <m/commandT/;
1500
else <m/commandF/;</cf> and you can use <cf>{ <m/command1/; <m/command2/;
1501
<M>...</M> }</cf> instead of either command. The <cf>else</cf> clause may be
1502
omitted. If the <cf><m>boolean expression</m></cf> is true, <m/commandT/ is
1503
executed, otherwise <m/commandF/ is executed.
1504

    
1505
<p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case
1506
<m/expr/ { else: | <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [
1507
... ] }</cf>. The expression after <cf>case</cf> can be of any type which can be
1508
on the left side of the &tilde; operator and anything that could be a member of
1509
a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/
1510
grouping. If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements
1511
between it and next <cf/:/ statement are executed. If <cf><m/expr/</cf> matches
1512
neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
1513

    
1514
<p>Here is example that uses <cf/if/ and <cf/case/ structures:
1515

    
1516
<code>
1517
case arg1 {
1518
	2: print "two"; print "I can do more commands without {}";
1519
	3 .. 5: print "three to five";
1520
	else: print "something else";
1521
}
1522

    
1523
if 1234 = i then printn "."; else {
1524
  print "not 1234";
1525
  print "You need {} around multiple commands";
1526
}
1527
</code>
1528

    
1529

    
1530
<sect>Route attributes
1531
<label id="route-attributes">
1532

    
1533
<p>A filter is implicitly passed a route, and it can access its attributes just
1534
like it accesses variables. Attempts to access undefined attribute result in a
1535
runtime error; you can check if an attribute is defined by using the
1536
<cf>defined( <m>attribute</m> )</cf> operator. One notable exception to this
1537
rule are attributes of bgppath and *clist types, where undefined value is
1538
regarded as empty bgppath/*clist for most purposes.
1539

    
1540
<descrip>
1541
	<tag><label id="rta-net"><m/prefix/ net</tag>
1542
	The network prefix or anything else the route is talking about. The
1543
	primary key of the routing table. Read-only. (See the <ref id="routes"
1544
	name="chapter about routes">.)
1545

    
1546
	<tag><label id="rta-scope"><m/enum/ scope</tag>
1547
	The scope of the route. Possible values: <cf/SCOPE_HOST/ for routes
1548
	local to this host, <cf/SCOPE_LINK/ for those specific for a physical
1549
	link, <cf/SCOPE_SITE/ and <cf/SCOPE_ORGANIZATION/ for private routes and
1550
	<cf/SCOPE_UNIVERSE/ for globally visible routes. This attribute is not
1551
	interpreted by BIRD and can be used to mark routes in filters. The
1552
	default value for new routes is <cf/SCOPE_UNIVERSE/.
1553

    
1554
	<tag><label id="rta-preference"><m/int/ preference</tag>
1555
	Preference of the route. Valid values are 0-65535. (See the chapter
1556
	about routing tables.)
1557

    
1558
	<tag><label id="rta-from"><m/ip/ from</tag>
1559
	The router which the route has originated from.
1560

    
1561
	<tag><label id="rta-gw"><m/ip/ gw</tag>
1562
	Next hop packets routed using this route should be forwarded to.
1563

    
1564
	<tag><label id="rta-proto"><m/string/ proto</tag>
1565
	The name of the protocol which the route has been imported from.
1566
	Read-only.
1567

    
1568
	<tag><label id="rta-source"><m/enum/ source</tag>
1569
	what protocol has told me about this route. Possible values:
1570
	<cf/RTS_DUMMY/, <cf/RTS_STATIC/, <cf/RTS_INHERIT/, <cf/RTS_DEVICE/,
1571
	<cf/RTS_STATIC_DEVICE/, <cf/RTS_REDIRECT/, <cf/RTS_RIP/, <cf/RTS_OSPF/,
1572
	<cf/RTS_OSPF_IA/, <cf/RTS_OSPF_EXT1/, <cf/RTS_OSPF_EXT2/, <cf/RTS_BGP/,
1573
	<cf/RTS_PIPE/, <cf/RTS_BABEL/.
1574

    
1575
	<tag><label id="rta-dest"><m/enum/ dest</tag>
1576
	Type of destination the packets should be sent to
1577
	(<cf/RTD_ROUTER/ for forwarding to a neighboring router,
1578
	<cf/RTD_DEVICE/ for routing to a directly-connected network,
1579
	<cf/RTD_MULTIPATH/ for multipath destinations,
1580
	<cf/RTD_BLACKHOLE/ for packets to be silently discarded,
1581
	<cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that should be
1582
	returned with ICMP host unreachable / ICMP administratively prohibited
1583
	messages). Can be changed, but only to <cf/RTD_BLACKHOLE/,
1584
	<cf/RTD_UNREACHABLE/ or <cf/RTD_PROHIBIT/.
1585

    
1586
	<tag><label id="rta-ifname"><m/string/ ifname</tag>
1587
	Name of the outgoing interface. Sink routes (like blackhole, unreachable
1588
	or prohibit) and multipath routes have no interface associated with
1589
	them, so <cf/ifname/ returns an empty string for such routes. Read-only.
1590

    
1591
	<tag><label id="rta-ifindex"><m/int/ ifindex</tag>
1592
	Index of the outgoing interface. System wide index of the interface. May
1593
	be used for interface matching, however indexes might change on interface
1594
	creation/removal. Zero is returned for routes with undefined outgoing
1595
	interfaces. Read-only.
1596

    
1597
	<tag><label id="rta-igp-metric"><m/int/ igp_metric</tag>
1598
	The optional attribute that can be used to specify a distance to the
1599
	network for routes that do not have a native protocol metric attribute
1600
	(like <cf/ospf_metric1/ for OSPF routes). It is used mainly by BGP to
1601
	compare internal distances to boundary routers (see below). It is also
1602
	used when the route is exported to OSPF as a default value for OSPF type
1603
	1 metric.
1604
</descrip>
1605

    
1606
<p>There also exist protocol-specific attributes which are described in the
1607
corresponding protocol sections.
1608

    
1609

    
1610
<sect>Other statements
1611
<label id="other-statements">
1612

    
1613
<p>The following statements are available:
1614

    
1615
<descrip>
1616
	<tag><label id="assignment"><m/variable/ = <m/expr/</tag>
1617
	Set variable to a given value.
1618

    
1619
	<tag><label id="filter-accept-reject">accept|reject [ <m/expr/ ]</tag>
1620
	Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
1621

    
1622
	<tag><label id="return">return <m/expr/</tag>
1623
	Return <cf><m>expr</m></cf> from the current function, the function ends
1624
	at this point.
1625

    
1626
	<tag><label id="print">print|printn <m/expr/ [<m/, expr.../]</tag>
1627
	Prints given expressions; useful mainly while debugging filters. The
1628
	<cf/printn/ variant does not terminate the line.
1629

    
1630
	<tag><label id="quitbird">quitbird</tag>
1631
	Terminates BIRD. Useful when debugging the filter interpreter.
1632
</descrip>
1633

    
1634

    
1635
<chapt>Protocols
1636
<label id="protocols">
1637

    
1638
<sect>Babel
1639
<label id="babel">
1640

    
1641
<sect1>Introduction
1642
<label id="babel-intro">
1643

    
1644
<p>The Babel protocol
1645
(<rfc id="6126">) is a loop-avoiding distance-vector routing protocol that is
1646
robust and efficient both in ordinary wired networks and in wireless mesh
1647
networks. Babel is conceptually very simple in its operation and "just works"
1648
in its default configuration, though some configuration is possible and in some
1649
cases desirable.
1650

    
1651
<p>The Babel protocol is dual stack; i.e., it can carry both IPv4 and IPv6
1652
routes over the same IPv6 transport. For sending and receiving Babel packets,
1653
only a link-local IPv6 address is needed.
1654

    
1655
<p>BIRD does not implement any Babel extensions, but will coexist with
1656
implementations using extensions (and will just ignore extension messages).
1657

    
1658
<sect1>Configuration
1659
<label id="babel-config">
1660

    
1661
<p>Babel supports no global configuration options apart from those common to all
1662
other protocols, but supports the following per-interface configuration options:
1663

    
1664
<code>
1665
protocol babel [<name>] {
1666
	ipv4 { <channel config> };
1667
	ipv6 { <channel config> };
1668
	interface <interface pattern> {
1669
		type <wired|wireless>;
1670
		rxcost <number>;
1671
		limit <number>;
1672
		hello interval <time>;
1673
		update interval <time>;
1674
		port <number>;
1675
		tx class|dscp <number>;
1676
		tx priority <number>;
1677
		rx buffer <number>;
1678
		tx length <number>;
1679
		check link <switch>;
1680
		next hop ipv4 <address>;
1681
		next hop ipv6 <address>;
1682
	};
1683
}
1684
</code>
1685

    
1686
<descrip>
1687
      <tag><label id="babel-channel">ipv4|ipv6 <m/channel config/</tag>
1688
      The supported channels are IPv4 and IPv6.
1689

    
1690
      <tag><label id="babel-type">type wired|wireless </tag>
1691
      This option specifies the interface type: Wired or wireless. On wired
1692
      interfaces a neighbor is considered unreachable after a small number of
1693
      Hello packets are lost, as described by <cf/limit/ option. On wireless
1694
      interfaces the ETX link quality estimation technique is used to compute
1695
      the metrics of routes discovered over this interface. This technique will
1696
      gradually degrade the metric of routes when packets are lost rather than
1697
      the more binary up/down mechanism of wired type links. Default:
1698
      <cf/wired/.
1699

    
1700
      <tag><label id="babel-rxcost">rxcost <m/num/</tag>
1701
      This option specifies the nominal RX cost of the interface. The effective
1702
      neighbor costs for route metrics will be computed from this value with a
1703
      mechanism determined by the interface <cf/type/. Note that in contrast to
1704
      other routing protocols like RIP or OSPF, the <cf/rxcost/ specifies the
1705
      cost of RX instead of TX, so it affects primarily neighbors' route
1706
      selection and not local route selection. Default: 96 for wired interfaces,
1707
      256 for wireless.
1708

    
1709
      <tag><label id="babel-limit">limit <m/num/</tag>
1710
      BIRD keeps track of received Hello messages from each neighbor to
1711
      establish neighbor reachability. For wired type interfaces, this option
1712
      specifies how many of last 16 hellos have to be correctly received in
1713
      order to neighbor is assumed to be up. The option is ignored on wireless
1714
      type interfaces, where gradual cost degradation is used instead of sharp
1715
      limit. Default: 12.
1716

    
1717
      <tag><label id="babel-hello">hello interval <m/time/ s|ms</tag>
1718
      Interval at which periodic Hello messages are sent on this interface,
1719
      with time units. Default: 4 seconds.
1720

    
1721
      <tag><label id="babel-update">update interval <m/time/ s|ms</tag>
1722
      Interval at which periodic (full) updates are sent, with time
1723
      units. Default: 4 times the hello interval.
1724

    
1725
      <tag><label id="babel-port">port <m/number/</tag>
1726
      This option selects an UDP port to operate on. The default is to operate
1727
      on port 6696 as specified in the Babel RFC.
1728

    
1729
      <tag><label id="babel-tx-class">tx class|dscp|priority <m/number/</tag>
1730
      These options specify the ToS/DiffServ/Traffic class/Priority of the
1731
      outgoing Babel packets. See <ref id="proto-tx-class" name="tx class"> common
1732
      option for detailed description.
1733

    
1734
      <tag><label id="babel-rx-buffer">rx buffer <m/number/</tag>
1735
      This option specifies the size of buffers used for packet processing.
1736
      The buffer size should be bigger than maximal size of received packets.
1737
      The default value is the interface MTU, and the value will be clamped to a
1738
      minimum of 512 bytes + IP packet overhead.
1739

    
1740
      <tag><label id="babel-tx-length">tx length <m/number/</tag>
1741
      This option specifies the maximum length of generated Babel packets. To
1742
      avoid IP fragmentation, it should not exceed the interface MTU value.
1743
      The default value is the interface MTU value, and the value will be
1744
      clamped to a minimum of 512 bytes + IP packet overhead.
1745

    
1746
      <tag><label id="babel-check-link">check link <m/switch/</tag>
1747
      If set, the hardware link state (as reported by OS) is taken into
1748
      consideration. When the link disappears (e.g. an ethernet cable is
1749
      unplugged), neighbors are immediately considered unreachable and all
1750
      routes received from them are withdrawn. It is possible that some
1751
      hardware drivers or platforms do not implement this feature. Default:
1752
      yes.
1753

    
1754
      <tag><label id="babel-next-hop-ipv4">next hop ipv4 <m/address/</tag>
1755
      Set the next hop address advertised for IPv4 routes advertised on this
1756
      interface. Default: the preferred IPv4 address of the interface.
1757

    
1758
      <tag><label id="babel-next-hop-ipv6">next hop ipv6 <m/address/</tag>
1759
      Set the next hop address advertised for IPv6 routes advertised on this
1760
      interface. If not set, the same link-local address that is used as the
1761
      source for Babel packets will be used. In normal operation, it should not
1762
      be necessary to set this option.
1763
</descrip>
1764

    
1765
<sect1>Attributes
1766
<label id="babel-attr">
1767

    
1768
<p>Babel defines just one attribute: the internal babel metric of the route. It
1769
is exposed as the <cf/babel_metric/ attribute and has range from 1 to infinity
1770
(65535).
1771

    
1772
<sect1>Example
1773
<label id="babel-exam">
1774

    
1775
<p><code>
1776
protocol babel {
1777
	interface "eth*" {
1778
		type wired;
1779
	};
1780
	interface "wlan0", "wlan1" {
1781
		type wireless;
1782
		hello interval 1;
1783
		rxcost 512;
1784
	};
1785
	interface "tap0";
1786

    
1787
	# This matches the default of babeld: redistribute all addresses
1788
	# configured on local interfaces, plus re-distribute all routes received
1789
	# from other babel peers.
1790

    
1791
	ipv4 {
1792
		export where (source = RTS_DEVICE) || (source = RTS_BABEL);
1793
	};
1794
	ipv6 {
1795
		export where (source = RTS_DEVICE) || (source = RTS_BABEL);
1796
	};
1797
}
1798
</code>
1799

    
1800
<sect1>Known issues
1801
<label id="babel-issues">
1802

    
1803
<p>When retracting a route, Babel generates an unreachable route for a little
1804
while (according to RFC). The interaction of this behavior with other protocols
1805
is not well tested and strange things may happen.
1806

    
1807

    
1808
<sect>BFD
1809
<label id="bfd">
1810

    
1811
<sect1>Introduction
1812
<label id="bfd-intro">
1813

    
1814
<p>Bidirectional Forwarding Detection (BFD) is not a routing protocol itself, it
1815
is an independent tool providing liveness and failure detection. Routing
1816
protocols like OSPF and BGP use integrated periodic "hello" messages to monitor
1817
liveness of neighbors, but detection times of these mechanisms are high (e.g. 40
1818
seconds by default in OSPF, could be set down to several seconds). BFD offers
1819
universal, fast and low-overhead mechanism for failure detection, which could be
1820
attached to any routing protocol in an advisory role.
1821

    
1822
<p>BFD consists of mostly independent BFD sessions. Each session monitors an
1823
unicast bidirectional path between two BFD-enabled routers. This is done by
1824
periodically sending control packets in both directions. BFD does not handle
1825
neighbor discovery, BFD sessions are created on demand by request of other
1826
protocols (like OSPF or BGP), which supply appropriate information like IP
1827
addresses and associated interfaces. When a session changes its state, these
1828
protocols are notified and act accordingly (e.g. break an OSPF adjacency when
1829
the BFD session went down).
1830

    
1831
<p>BIRD implements basic BFD behavior as defined in <rfc id="5880"> (some
1832
advanced features like the echo mode or authentication are not implemented), IP
1833
transport for BFD as defined in <rfc id="5881"> and <rfc id="5883"> and
1834
interaction with client protocols as defined in <rfc id="5882">.
1835
We currently support at most one protocol instance.
1836

    
1837
<p>BFD packets are sent with a dynamic source port number. Linux systems use by
1838
default a bit different dynamic port range than the IANA approved one
1839
(49152-65535). If you experience problems with compatibility, please adjust
1840
<cf>/proc/sys/net/ipv4/ip_local_port_range</cf>
1841

    
1842
<sect1>Configuration
1843
<label id="bfd-config">
1844

    
1845
<p>BFD configuration consists mainly of multiple definitions of interfaces.
1846
Most BFD config options are session specific. When a new session is requested
1847
and dynamically created, it is configured from one of these definitions. For
1848
sessions to directly connected neighbors, <cf/interface/ definitions are chosen
1849
based on the interface associated with the session, while <cf/multihop/
1850
definition is used for multihop sessions. If no definition is relevant, the
1851
session is just created with the default configuration. Therefore, an empty BFD
1852
configuration is often sufficient.
1853

    
1854
<p>Note that to use BFD for other protocols like OSPF or BGP, these protocols
1855
also have to be configured to request BFD sessions, usually by <cf/bfd/ option.
1856

    
1857
<p>Some of BFD session options require <m/time/ value, which has to be specified
1858
with the appropriate unit: <m/num/ <cf/s/|<cf/ms/|<cf/us/. Although microseconds
1859
are allowed as units, practical minimum values are usually in order of tens of
1860
milliseconds.
1861

    
1862
<code>
1863
protocol bfd [&lt;name&gt;] {
1864
	interface &lt;interface pattern&gt; {
1865
		interval &lt;time&gt;;
1866
		min rx interval &lt;time&gt;;
1867
		min tx interval &lt;time&gt;;
1868
		idle tx interval &lt;time&gt;;
1869
		multiplier &lt;num&gt;;
1870
		passive &lt;switch&gt;;
1871
		authentication none;
1872
		authentication simple;
1873
		authentication [meticulous] keyed md5|sha1;
1874
		password "&lt;text&gt;";
1875
		password "&lt;text&gt;" {
1876
			id &lt;num&gt;;
1877
			generate from "&lt;date&gt;";
1878
			generate to "&lt;date&gt;";
1879
			accept from "&lt;date&gt;";
1880
			accept to "&lt;date&gt;";
1881
			from "&lt;date&gt;";
1882
			to "&lt;date&gt;";
1883
		};
1884
	};
1885
	multihop {
1886
		interval &lt;time&gt;;
1887
		min rx interval &lt;time&gt;;
1888
		min tx interval &lt;time&gt;;
1889
		idle tx interval &lt;time&gt;;
1890
		multiplier &lt;num&gt;;
1891
		passive &lt;switch&gt;;
1892
	};
1893
	neighbor &lt;ip&gt; [dev "&lt;interface&gt;"] [local &lt;ip&gt;] [multihop &lt;switch&gt;];
1894
}
1895
</code>
1896

    
1897
<descrip>
1898
	<tag><label id="bfd-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
1899
	Interface definitions allow to specify options for sessions associated
1900
	with such interfaces and also may contain interface specific options.
1901
	See <ref id="proto-iface" name="interface"> common option for a detailed
1902
	description of interface patterns. Note that contrary to the behavior of
1903
	<cf/interface/ definitions of other protocols, BFD protocol would accept
1904
	sessions (in default configuration) even on interfaces not covered by
1905
	such definitions.
1906

    
1907
	<tag><label id="bfd-multihop">multihop { <m/options/ }</tag>
1908
	Multihop definitions allow to specify options for multihop BFD sessions,
1909
	in the same manner as <cf/interface/ definitions are used for directly
1910
	connected sessions. Currently only one such definition (for all multihop
1911
	sessions) could be used.
1912

    
1913
	<tag><label id="bfd-neighbor">neighbor <m/ip/ [dev "<m/interface/"] [local <m/ip/] [multihop <m/switch/]</tag>
1914
	BFD sessions are usually created on demand as requested by other
1915
	protocols (like OSPF or BGP). This option allows to explicitly add
1916
	a BFD session to the specified neighbor regardless of such requests.
1917

    
1918
	The session is identified by the IP address of the neighbor, with
1919
	optional specification of used interface and local IP. By default
1920
	the neighbor must be directly connected, unless the session is
1921
	configured as multihop. Note that local IP must be specified for
1922
	multihop sessions.
1923
</descrip>
1924

    
1925
<p>Session specific options (part of <cf/interface/ and <cf/multihop/ definitions):
1926

    
1927
<descrip>
1928
	<tag><label id="bfd-interval">interval <m/time/</tag>
1929
	BFD ensures availability of the forwarding path associated with the
1930
	session by periodically sending BFD control packets in both
1931
	directions. The rate of such packets is controlled by two options,
1932
	<cf/min rx interval/ and <cf/min tx interval/ (see below). This option
1933
	is just a shorthand to set both of these options together.
1934

    
1935
	<tag><label id="bfd-min-rx-interval">min rx interval <m/time/</tag>
1936
	This option specifies the minimum RX interval, which is announced to the
1937
	neighbor and used there to limit the neighbor's rate of generated BFD
1938
	control packets. Default: 10 ms.
1939

    
1940
	<tag><label id="bfd-min-tx-interval">min tx interval <m/time/</tag>
1941
	This option specifies the desired TX interval, which controls the rate
1942
	of generated BFD control packets (together with <cf/min rx interval/
1943
	announced by the neighbor). Note that this value is used only if the BFD
1944
	session is up, otherwise the value of <cf/idle tx interval/ is used
1945
	instead. Default: 100 ms.
1946

    
1947
	<tag><label id="bfd-idle-tx-interval">idle tx interval <m/time/</tag>
1948
	In order to limit unnecessary traffic in cases where a neighbor is not
1949
	available or not running BFD, the rate of generated BFD control packets
1950
	is lower when the BFD session is not up. This option specifies the
1951
	desired TX interval in such cases instead of <cf/min tx interval/.
1952
	Default: 1 s.
1953

    
1954
	<tag><label id="bfd-multiplier">multiplier <m/num/</tag>
1955
	Failure detection time for BFD sessions is based on established rate of
1956
	BFD control packets (<cf>min rx/tx interval</cf>) multiplied by this
1957
	multiplier, which is essentially (ignoring jitter) a number of missed
1958
	packets after which the session is declared down. Note that rates and
1959
	multipliers could be different in each direction of a BFD session.
1960
	Default: 5.
1961

    
1962
	<tag><label id="bfd-passive">passive <m/switch/</tag>
1963
	Generally, both BFD session endpoints try to establish the session by
1964
	sending control packets to the other side. This option allows to enable
1965
	passive mode, which means that the router does not send BFD packets
1966
	until it has received one from the other side. Default: disabled.
1967

    
1968
	<tag>authentication none</tag>
1969
	No passwords are sent in BFD packets. This is the default value.
1970

    
1971
	<tag>authentication simple</tag>
1972
	Every packet carries 16 bytes of password. Received packets lacking this
1973
	password are ignored. This authentication mechanism is very weak.
1974

    
1975
	<tag>authentication [meticulous] keyed md5|sha1</tag>
1976
	An authentication code is appended to each packet. The cryptographic
1977
	algorithm is keyed MD5 or keyed SHA-1. Note that the algorithm is common
1978
	for all keys (on one interface), in contrast to OSPF or RIP, where it
1979
	is a per-key option. Passwords (keys) are not sent open via network.
1980

    
1981
	The <cf/meticulous/ variant means that cryptographic sequence numbers
1982
	are increased for each sent packet, while in the basic variant they are
1983
	increased about once per second. Generally, the <cf/meticulous/ variant
1984
	offers better resistance to replay attacks but may require more
1985
	computation.
1986

    
1987
	<tag>password "<M>text</M>"</tag>
1988
	Specifies a password used for authentication. See <ref id="proto-pass"
1989
	name="password"> common option for detailed description. Note that
1990
	password option <cf/algorithm/ is not available in BFD protocol. The
1991
	algorithm is selected by <cf/authentication/ option for all passwords.
1992

    
1993
</descrip>
1994

    
1995
<sect1>Example
1996
<label id="bfd-exam">
1997

    
1998
<p><code>
1999
protocol bfd {
2000
	interface "eth*" {
2001
		min rx interval 20 ms;
2002
		min tx interval 50 ms;
2003
		idle tx interval 300 ms;
2004
	};
2005
	interface "gre*" {
2006
		interval 200 ms;
2007
		multiplier 10;
2008
		passive;
2009
	};
2010
	multihop {
2011
		interval 200 ms;
2012
		multiplier 10;
2013
	};
2014

    
2015
	neighbor 192.168.1.10;
2016
	neighbor 192.168.2.2 dev "eth2";
2017
	neighbor 192.168.10.1 local 192.168.1.1 multihop;
2018
}
2019
</code>
2020

    
2021

    
2022
<sect>BGP
2023
<label id="bgp">
2024

    
2025
<p>The Border Gateway Protocol is the routing protocol used for backbone level
2026
routing in the today's Internet. Contrary to other protocols, its convergence
2027
does not rely on all routers following the same rules for route selection,
2028
making it possible to implement any routing policy at any router in the network,
2029
the only restriction being that if a router advertises a route, it must accept
2030
and forward packets according to it.
2031

    
2032
<p>BGP works in terms of autonomous systems (often abbreviated as AS). Each AS
2033
is a part of the network with common management and common routing policy. It is
2034
identified by a unique 16-bit number (ASN). Routers within each AS usually
2035
exchange AS-internal routing information with each other using an interior
2036
gateway protocol (IGP, such as OSPF or RIP). Boundary routers at the border of
2037
the AS communicate global (inter-AS) network reachability information with their
2038
neighbors in the neighboring AS'es via exterior BGP (eBGP) and redistribute
2039
received information to other routers in the AS via interior BGP (iBGP).
2040

    
2041
<p>Each BGP router sends to its neighbors updates of the parts of its routing
2042
table it wishes to export along with complete path information (a list of AS'es
2043
the packet will travel through if it uses the particular route) in order to
2044
avoid routing loops.
2045

    
2046
<sect1>Supported standards
2047
<label id="bgp-standards">
2048

    
2049
<p>
2050
<itemize>
2051
<item> <rfc id="4271"> - Border Gateway Protocol 4 (BGP)
2052
<item> <rfc id="1997"> - BGP Communities Attribute
2053
<item> <rfc id="2385"> - Protection of BGP Sessions via TCP MD5 Signature
2054
<item> <rfc id="2545"> - Use of BGP Multiprotocol Extensions for IPv6
2055
<item> <rfc id="2918"> - Route Refresh Capability
2056
<item> <rfc id="3107"> - Carrying Label Information in BGP
2057
<item> <rfc id="4360"> - BGP Extended Communities Attribute
2058
<item> <rfc id="4364"> - BGP/MPLS IPv4 Virtual Private Networks
2059
<item> <rfc id="4456"> - BGP Route Reflection
2060
<item> <rfc id="4486"> - Subcodes for BGP Cease Notification Message
2061
<item> <rfc id="4659"> - BGP/MPLS IPv6 Virtual Private Networks
2062
<item> <rfc id="4724"> - Graceful Restart Mechanism for BGP
2063
<item> <rfc id="4760"> - Multiprotocol extensions for BGP
2064
<item> <rfc id="4798"> - Connecting IPv6 Islands over IPv4 MPLS
2065
<item> <rfc id="5065"> - AS confederations for BGP
2066
<item> <rfc id="5082"> - Generalized TTL Security Mechanism
2067
<item> <rfc id="5492"> - Capabilities Advertisement with BGP
2068
<item> <rfc id="5549"> - Advertising IPv4 NLRI with an IPv6 Next Hop
2069
<item> <rfc id="5575"> - Dissemination of Flow Specification Rules
2070
<item> <rfc id="5668"> - 4-Octet AS Specific BGP Extended Community
2071
<item> <rfc id="6286"> - AS-Wide Unique BGP Identifier
2072
<item> <rfc id="6608"> - Subcodes for BGP Finite State Machine Error
2073
<item> <rfc id="6793"> - BGP Support for 4-Octet AS Numbers
2074
<item> <rfc id="7313"> - Enhanced Route Refresh Capability for BGP
2075
<item> <rfc id="7606"> - Revised Error Handling for BGP UPDATE Messages
2076
<item> <rfc id="7911"> - Advertisement of Multiple Paths in BGP
2077
<item> <rfc id="7947"> - Internet Exchange BGP Route Server
2078
<item> <rfc id="8092"> - BGP Large Communities Attribute
2079
<item> <rfc id="8203"> - BGP Administrative Shutdown Communication
2080
<item> <rfc id="8212"> - Default EBGP Route Propagation Behavior without Policies
2081
</itemize>
2082

    
2083
<sect1>Route selection rules
2084
<label id="bgp-route-select-rules">
2085

    
2086
<p>BGP doesn't have any simple metric, so the rules for selection of an optimal
2087
route among multiple BGP routes with the same preference are a bit more complex
2088
and they are implemented according to the following algorithm. It starts the
2089
first rule, if there are more "best" routes, then it uses the second rule to
2090
choose among them and so on.
2091

    
2092
<itemize>
2093
	<item>Prefer route with the highest Local Preference attribute.
2094
	<item>Prefer route with the shortest AS path.
2095
	<item>Prefer IGP origin over EGP and EGP origin over incomplete.
2096
	<item>Prefer the lowest value of the Multiple Exit Discriminator.
2097
	<item>Prefer routes received via eBGP over ones received via iBGP.
2098
	<item>Prefer routes with lower internal distance to a boundary router.
2099
	<item>Prefer the route with the lowest value of router ID of the
2100
	advertising router.
2101
</itemize>
2102

    
2103
<sect1>IGP routing table
2104
<label id="bgp-igp-routing-table">
2105

    
2106
<p>BGP is mainly concerned with global network reachability and with routes to
2107
other autonomous systems. When such routes are redistributed to routers in the
2108
AS via BGP, they contain IP addresses of a boundary routers (in route attribute
2109
NEXT_HOP). BGP depends on existing IGP routing table with AS-internal routes to
2110
determine immediate next hops for routes and to know their internal distances to
2111
boundary routers for the purpose of BGP route selection. In BIRD, there is
2112
usually one routing table used for both IGP routes and BGP routes.
2113

    
2114
<sect1>Protocol configuration
2115
<label id="bgp-proto-config">
2116

    
2117
<p>Each instance of the BGP corresponds to one neighboring router. This allows
2118
to set routing policy and all the other parameters differently for each neighbor
2119
using the following configuration parameters:
2120

    
2121
<descrip>
2122
	<tag><label id="bgp-local">local [<m/ip/] as <m/number/</tag>
2123
	Define which AS we are part of. (Note that contrary to other IP routers,
2124
	BIRD is able to act as a router located in multiple AS'es simultaneously,
2125
	but in such cases you need to tweak the BGP paths manually in the filters
2126
	to get consistent behavior.) Optional <cf/ip/ argument specifies a source
2127
	address, equivalent to the <cf/source address/ option (see below). This
2128
	parameter is mandatory.
2129

    
2130
	<tag><label id="bgp-neighbor">neighbor [<m/ip/] [port <m/number/] [as <m/number/]</tag>
2131
	Define neighboring router this instance will be talking to and what AS
2132
	it is located in. In case the neighbor is in the same AS as we are, we
2133
	automatically switch to iBGP. Optionally, the remote port may also be
2134
	specified. The parameter may be used multiple times with different
2135
	sub-options (e.g., both <cf/neighbor 10.0.0.1 as 65000;/ and
2136
	<cf/neighbor 10.0.0.1; neighbor as 65000;/ are valid). This parameter is
2137
	mandatory.
2138

    
2139
	<tag><label id="bgp-iface">interface <m/string/</tag>
2140
	Define interface we should use for link-local BGP IPv6 sessions.
2141
	Interface can also be specified as a part of <cf/neighbor address/
2142
	(e.g., <cf/neighbor fe80::1234%eth0 as 65000;/). The option may also be
2143
	used for non link-local sessions when it is necessary to explicitly
2144
	specify an interface, but only for direct (not multihop) sessions.
2145

    
2146
	<tag><label id="bgp-direct">direct</tag>
2147
	Specify that the neighbor is directly connected. The IP address of the
2148
	neighbor must be from a directly reachable IP range (i.e. associated
2149
	with one of your router's interfaces), otherwise the BGP session
2150
	wouldn't start but it would wait for such interface to appear. The
2151
	alternative is the <cf/multihop/ option. Default: enabled for eBGP.
2152

    
2153
	<tag><label id="bgp-multihop">multihop [<m/number/]</tag>
2154
	Configure multihop BGP session to a neighbor that isn't directly
2155
	connected. Accurately, this option should be used if the configured
2156
	neighbor IP address does not match with any local network subnets. Such
2157
	IP address have to be reachable through system routing table. The
2158
	alternative is the <cf/direct/ option. For multihop BGP it is
2159
	recommended to explicitly configure the source address to have it
2160
	stable. Optional <cf/number/ argument can be used to specify the number
2161
	of hops (used for TTL). Note that the number of networks (edges) in a
2162
	path is counted; i.e., if two BGP speakers are separated by one router,
2163
	the number of hops is 2. Default: enabled for iBGP.
2164

    
2165
	<tag><label id="bgp-source-address">source address <m/ip/</tag>
2166
	Define local address we should use for next hop calculation and as a
2167
	source address for the BGP session. Default: the address of the local
2168
	end of the interface our neighbor is connected to.
2169

    
2170
	<tag><label id="bgp-strict-bind">strict bind <m/switch/</tag>
2171
	Specify whether BGP listening socket should be bound to a specific local
2172
	address (the same as the <cf/source address/) and associated interface,
2173
	or to all addresses. Binding to a specific address could be useful in
2174
	cases like running multiple BIRD instances on a machine, each using its
2175
	IP address. Note that listening sockets bound to a specific address and
2176
	to all addresses collide, therefore either all BGP protocols (of the
2177
	same address family and using the same local port) should have set
2178
	<cf/strict bind/, or none of them. Default: disabled.
2179

    
2180
	<tag><label id="bgp-check-link">check link <M>switch</M></tag>
2181
	BGP could use hardware link state into consideration.  If enabled,
2182
	BIRD tracks the link state of the associated interface and when link
2183
	disappears (e.g. an ethernet cable is unplugged), the BGP session is
2184
	immediately shut down. Note that this option cannot be used with
2185
	multihop BGP. Default: enabled for direct BGP, disabled otherwise.
2186

    
2187
	<tag><label id="bgp-bfd">bfd <M>switch</M></tag>
2188
	BGP could use BFD protocol as an advisory mechanism for neighbor
2189
	liveness and failure detection. If enabled, BIRD setups a BFD session
2190
	for the BGP neighbor and tracks its liveness by it. This has an
2191
	advantage of an order of magnitude lower detection times in case of
2192
	failure. Note that BFD protocol also has to be configured, see
2193
	<ref id="bfd" name="BFD"> section for details. Default: disabled.
2194

    
2195
	<tag><label id="bgp-ttl-security">ttl security <m/switch/</tag>
2196
	Use GTSM (<rfc id="5082"> - the generalized TTL security mechanism). GTSM
2197
	protects against spoofed packets by ignoring received packets with a
2198
	smaller than expected TTL. To work properly, GTSM have to be enabled on
2199
	both sides of a BGP session. If both <cf/ttl security/ and
2200
	<cf/multihop/ options are enabled, <cf/multihop/ option should specify
2201
	proper hop value to compute expected TTL. Kernel support required:
2202
	Linux: 2.6.34+ (IPv4), 2.6.35+ (IPv6), BSD: since long ago, IPv4 only.
2203
	Note that full (ICMP protection, for example) <rfc id="5082"> support is
2204
	provided by Linux only. Default: disabled.
2205

    
2206
	<tag><label id="bgp-password">password <m/string/</tag>
2207
	Use this password for MD5 authentication of BGP sessions (<rfc id="2385">). When
2208
	used on BSD systems, see also <cf/setkey/ option below. Default: no
2209
	authentication.
2210

    
2211
	<tag><label id="bgp-setkey">setkey <m/switch/</tag>
2212
	On BSD systems, keys for TCP MD5 authentication are stored in the global
2213
	SA/SP database, which can be accessed by external utilities (e.g.
2214
	setkey(8)). BIRD configures security associations in the SA/SP database
2215
	automatically based on <cf/password/ options (see above), this option
2216
	allows to disable automatic updates by BIRD when manual configuration by
2217
	external utilities is preferred. Note that automatic SA/SP database
2218
	updates are currently implemented only for FreeBSD. Passwords have to be
2219
	set manually by an external utility on NetBSD and OpenBSD. Default:
2220
	enabled (ignored on non-FreeBSD).
2221

    
2222
	<tag><label id="bgp-passive">passive <m/switch/</tag>
2223
	Standard BGP behavior is both initiating outgoing connections and
2224
	accepting incoming connections. In passive mode, outgoing connections
2225
	are not initiated. Default: off.
2226

    
2227
	<tag><label id="bgp-confederation">confederation <m/number/</tag>
2228
	BGP confederations (<rfc id="5065">) are collections of autonomous
2229
	systems that act as one entity to external systems, represented by one
2230
	confederation identifier (instead of AS numbers). This option allows to
2231
	enable BGP confederation behavior and to specify the local confederation
2232
	identifier. When BGP confederations are used, all BGP speakers that are
2233
	members of the BGP confederation should have the same confederation
2234
	identifier configured. Default: 0 (no confederation).
2235

    
2236
	<tag><label id="bgp-confederation-member">confederation member <m/switch/</tag>
2237
	When BGP confederations are used, this option allows to specify whether
2238
	the BGP neighbor is a member of the same confederation as the local BGP
2239
	speaker. The option is unnecessary (and ignored) for IBGP sessions, as
2240
	the same AS number implies the same confederation. Default: no.
2241

    
2242
	<tag><label id="bgp-rr-client">rr client</tag>
2243
	Be a route reflector and treat the neighbor as a route reflection
2244
	client. Default: disabled.
2245

    
2246
	<tag><label id="bgp-rr-cluster-id">rr cluster id <m/IPv4 address/</tag>
2247
	Route reflectors use cluster id to avoid route reflection loops. When
2248
	there is one route reflector in a cluster it usually uses its router id
2249
	as a cluster id, but when there are more route reflectors in a cluster,
2250
	these need to be configured (using this option) to use a common cluster
2251
	id. Clients in a cluster need not know their cluster id and this option
2252
	is not allowed for them. Default: the same as router id.
2253

    
2254
	<tag><label id="bgp-rs-client">rs client</tag>
2255
	Be a route server and treat the neighbor as a route server client.
2256
	A route server is used as a replacement for full mesh EBGP routing in
2257
	Internet exchange points in a similar way to route reflectors used in
2258
	IBGP routing. BIRD does not implement obsoleted <rfc id="1863">, but
2259
	uses ad-hoc implementation, which behaves like plain EBGP but reduces
2260
	modifications to advertised route attributes to be transparent (for
2261
	example does not prepend its AS number to AS PATH attribute and
2262
	keeps MED attribute). Default: disabled.
2263

    
2264
	<tag><label id="bgp-allow-local-pref">allow bgp_local_pref <m/switch/</tag>
2265
	A standard BGP implementation do not send the Local Preference attribute
2266
	to eBGP neighbors and ignore this attribute if received from eBGP
2267
	neighbors, as per <rfc id="4271">.  When this option is enabled on an
2268
	eBGP session, this attribute will be sent to and accepted from the peer,
2269
	which is useful for example if you have a setup like in <rfc id="7938">.
2270
	The option does not affect iBGP sessions. Default: off.
2271

    
2272
	<tag><label id="bgp-allow-local-as">allow local as [<m/number/]</tag>
2273
	BGP prevents routing loops by rejecting received routes with the local
2274
	AS number in the AS path. This option allows to loose or disable the
2275
	check. Optional <cf/number/ argument can be used to specify the maximum
2276
	number of local ASNs in the AS path that is allowed for received
2277
	routes. When the option is used without the argument, the check is
2278
	completely disabled and you should ensure loop-free behavior by some
2279
	other means. Default: 0 (no local AS number allowed).
2280

    
2281
	<tag><label id="bgp-enable-route-refresh">enable route refresh <m/switch/</tag>
2282
	After the initial route exchange, BGP protocol uses incremental updates
2283
	to keep BGP speakers synchronized. Sometimes (e.g., if BGP speaker
2284
	changes its import filter, or if there is suspicion of inconsistency) it
2285
	is necessary to do a new complete route exchange. BGP protocol extension
2286
	Route Refresh (<rfc id="2918">) allows BGP speaker to request
2287
	re-advertisement of all routes from its neighbor. BGP protocol
2288
	extension Enhanced Route Refresh (<rfc id="7313">) specifies explicit
2289
	begin and end for such exchanges, therefore the receiver can remove
2290
	stale routes that were not advertised during the exchange. This option
2291
	specifies whether BIRD advertises these capabilities and supports
2292
	related procedures. Note that even when disabled, BIRD can send route
2293
	refresh requests.  Default: on.
2294

    
2295
	<tag><label id="bgp-graceful-restart">graceful restart <m/switch/|aware</tag>
2296
	When a BGP speaker restarts or crashes, neighbors will discard all
2297
	received paths from the speaker, which disrupts packet forwarding even
2298
	when the forwarding plane of the speaker remains intact. <rfc id="4724">
2299
	specifies an optional graceful restart mechanism to alleviate this
2300
	issue. This option controls the mechanism. It has three states:
2301
	Disabled, when no support is provided. Aware, when the graceful restart
2302
	support is announced and the support for restarting neighbors is
2303
	provided, but no local graceful restart is allowed (i.e. receiving-only
2304
	role). Enabled, when the full graceful restart support is provided
2305
	(i.e. both restarting and receiving role). Restarting role could be also
2306
	configured per-channel. Note that proper support for local graceful
2307
	restart requires also configuration of other protocols. Default: aware.
2308

    
2309
	<tag><label id="bgp-graceful-restart-time">graceful restart time <m/number/</tag>
2310
	The restart time is announced in the BGP graceful restart capability
2311
	and specifies how long the neighbor would wait for the BGP session to
2312
	re-establish after a restart before deleting stale routes. Default:
2313
	120 seconds.
2314

    
2315
	<tag><label id="bgp-interpret-communities">interpret communities <m/switch/</tag>
2316
	<rfc id="1997"> demands that BGP speaker should process well-known
2317
	communities like no-export (65535, 65281) or no-advertise (65535,
2318
	65282). For example, received route carrying a no-adverise community
2319
	should not be advertised to any of its neighbors. If this option is
2320
	enabled (which is by default), BIRD has such behavior automatically (it
2321
	is evaluated when a route is exported to the BGP protocol just before
2322
	the export filter).  Otherwise, this integrated processing of
2323
	well-known communities is disabled. In that case, similar behavior can
2324
	be implemented in the export filter.  Default: on.
2325

    
2326
	<tag><label id="bgp-enable-as4">enable as4 <m/switch/</tag>
2327
	BGP protocol was designed to use 2B AS numbers and was extended later to
2328
	allow 4B AS number. BIRD supports 4B AS extension, but by disabling this
2329
	option it can be persuaded not to advertise it and to maintain old-style
2330
	sessions with its neighbors. This might be useful for circumventing bugs
2331
	in neighbor's implementation of 4B AS extension. Even when disabled
2332
	(off), BIRD behaves internally as AS4-aware BGP router. Default: on.
2333

    
2334
	<tag><label id="bgp-enable-extended-messages">enable extended messages <m/switch/</tag>
2335
	The BGP protocol uses maximum message length of 4096 bytes. This option
2336
	provides an extension to allow extended messages with length up
2337
	to 65535 bytes. Default: off.
2338

    
2339
	<tag><label id="bgp-capabilities">capabilities <m/switch/</tag>
2340
	Use capability advertisement to advertise optional capabilities. This is
2341
	standard behavior for newer BGP implementations, but there might be some
2342
	older BGP implementations that reject such connection attempts. When
2343
	disabled (off), features that request it (4B AS support) are also
2344
	disabled. Default: on, with automatic fallback to off when received
2345
	capability-related error.
2346

    
2347
	<tag><label id="bgp-advertise-ipv4">advertise ipv4 <m/switch/</tag>
2348
	Advertise IPv4 multiprotocol capability. This is not a correct behavior
2349
	according to the strict interpretation of <rfc id="4760">, but it is
2350
	widespread and required by some BGP implementations (Cisco and Quagga).
2351
	This option is relevant to IPv4 mode with enabled capability
2352
	advertisement only. Default: on.
2353

    
2354
	<tag><label id="bgp-disable-after-error">disable after error <m/switch/</tag>
2355
	When an error is encountered (either locally or by the other side),
2356
	disable the instance automatically and wait for an administrator to fix
2357
	the problem manually. Default: off.
2358

    
2359
	<tag><label id="bgp-hold-time">hold time <m/number/</tag>
2360
	Time in seconds to wait for a Keepalive message from the other side
2361
	before considering the connection stale. Default: depends on agreement
2362
	with the neighboring router, we prefer 240 seconds if the other side is
2363
	willing to accept it.
2364

    
2365
	<tag><label id="bgp-startup-hold-time">startup hold time <m/number/</tag>
2366
	Value of the hold timer used before the routers have a chance to exchange
2367
	open messages and agree on the real value. Default: 240	seconds.
2368

    
2369
	<tag><label id="bgp-keepalive-time">keepalive time <m/number/</tag>
2370
	Delay in seconds between sending of two consecutive Keepalive messages.
2371
	Default: One third of the hold time.
2372

    
2373
	<tag><label id="bgp-connect-delay-time">connect delay time <m/number/</tag>
2374
	Delay in seconds between protocol startup and the first attempt to
2375
	connect. Default: 5 seconds.
2376

    
2377
	<tag><label id="bgp-connect-retry-time">connect retry time <m/number/</tag>
2378
	Time in seconds to wait before retrying a failed attempt to connect.
2379
	Default: 120 seconds.
2380

    
2381
	<tag><label id="bgp-error-wait-time">error wait time <m/number/,<m/number/</tag>
2382
	Minimum and maximum delay in seconds between a protocol failure (either
2383
	local or reported by the peer) and automatic restart. Doesn't apply
2384
	when <cf/disable after error/ is configured. If consecutive errors
2385
	happen, the delay is increased exponentially until it reaches the
2386
	maximum. Default: 60, 300.
2387

    
2388
	<tag><label id="bgp-error-forget-time">error forget time <m/number/</tag>
2389
	Maximum time in seconds between two protocol failures to treat them as a
2390
	error sequence which makes <cf/error wait time/ increase exponentially.
2391
	Default: 300 seconds.
2392

    
2393
	<tag><label id="bgp-path-metric">path metric <m/switch/</tag>
2394
	Enable comparison of path lengths when deciding which BGP route is the
2395
	best one. Default: on.
2396

    
2397
	<tag><label id="bgp-med-metric">med metric <m/switch/</tag>
2398
	Enable comparison of MED attributes (during best route selection) even
2399
	between routes received from different ASes. This may be useful if all
2400
	MED attributes contain some consistent metric, perhaps enforced in
2401
	import filters of AS boundary routers. If this option is disabled, MED
2402
	attributes are compared only if routes are received from the same AS
2403
	(which is the standard behavior). Default: off.
2404

    
2405
	<tag><label id="bgp-deterministic-med">deterministic med <m/switch/</tag>
2406
	BGP route selection algorithm is often viewed as a comparison between
2407
	individual routes (e.g. if a new route appears and is better than the
2408
	current best one, it is chosen as the new best one). But the proper
2409
	route selection, as specified by <rfc id="4271">, cannot be fully
2410
	implemented in that way. The problem is mainly in handling the MED
2411
	attribute. BIRD, by default, uses an simplification based on individual
2412
	route comparison, which in some cases may lead to temporally dependent
2413
	behavior (i.e. the selection is dependent on the order in which routes
2414
	appeared). This option enables a different (and slower) algorithm
2415
	implementing proper <rfc id="4271"> route selection, which is
2416
	deterministic. Alternative way how to get deterministic behavior is to
2417
	use <cf/med metric/ option. This option is incompatible with <ref
2418
	id="dsc-table-sorted" name="sorted tables">.  Default: off.
2419

    
2420
	<tag><label id="bgp-igp-metric">igp metric <m/switch/</tag>
2421
	Enable comparison of internal distances to boundary routers during best
2422
	route selection. Default: on.
2423

    
2424
	<tag><label id="bgp-prefer-older">prefer older <m/switch/</tag>
2425
	Standard route selection algorithm breaks ties by comparing router IDs.
2426
	This changes the behavior to prefer older routes (when both are external
2427
	and from different peer). For details, see <rfc id="5004">. Default: off.
2428

    
2429
	<tag><label id="bgp-default-med">default bgp_med <m/number/</tag>
2430
	Value of the Multiple Exit Discriminator to be used during route
2431
	selection when the MED attribute is missing. Default: 0.
2432

    
2433
	<tag><label id="bgp-default-local-pref">default bgp_local_pref <m/number/</tag>
2434
	A default value for the Local Preference attribute. It is used when
2435
	a new Local Preference attribute is attached to a route by the BGP
2436
	protocol itself (for example, if a route is received through eBGP and
2437
	therefore does not have such attribute). Default: 100 (0 in pre-1.2.0
2438
	versions of BIRD).
2439
</descrip>
2440

    
2441
<sect1>Channel configuration
2442
<label id="bgp-channel-config">
2443

    
2444
<p>BGP supports several AFIs and SAFIs over one connection. Every AFI/SAFI
2445
announced to the peer corresponds to one channel. The table of supported AFI/SAFIs
2446
together with their appropriate channels follows.
2447

    
2448
<table loc="h">
2449
<tabular ca="l|l|l|r|r">
2450
  <bf/Channel name/   | <bf/Table nettype/ | <bf/IGP table allowed/  | <bf/AFI/ | <bf/SAFI/
2451
@<hline>
2452
  <cf/ipv4/	      | <cf/ipv4/          | <cf/ipv4/ and <cf/ipv6/ | 1        | 1
2453
@ <cf/ipv6/           | <cf/ipv6/          | <cf/ipv4/ and <cf/ipv6/ | 2        | 1
2454
@ <cf/ipv4 multicast/ | <cf/ipv4/          | <cf/ipv4/ and <cf/ipv6/ | 1        | 2
2455
@ <cf/ipv6 multicast/ | <cf/ipv6/          | <cf/ipv4/ and <cf/ipv6/ | 2        | 2
2456
@ <cf/ipv4 mpls/      | <cf/ipv4/          | <cf/ipv4/ and <cf/ipv6/ | 1        | 4
2457
@ <cf/ipv6 mpls/      | <cf/ipv6/          | <cf/ipv4/ and <cf/ipv6/ | 2        | 4
2458
@ <cf/vpn4 mpls/      | <cf/vpn4/          | <cf/ipv4/ and <cf/ipv6/ | 1        | 128
2459
@ <cf/vpn6 mpls/      | <cf/vpn6/          | <cf/ipv4/ and <cf/ipv6/ | 2        | 128
2460
@ <cf/vpn4 multicast/ | <cf/vpn4/          | <cf/ipv4/ and <cf/ipv6/ | 1        | 129
2461
@ <cf/vpn6 multicast/ | <cf/vpn6/          | <cf/ipv4/ and <cf/ipv6/ | 2        | 129
2462
@ <cf/flow4/	      | <cf/flow4/         | ---                     | 1        | 133
2463
@ <cf/flow6/          | <cf/flow6/         | ---                     | 2        | 133
2464
</tabular>
2465
</table>
2466

    
2467
<p>Due to <rfc id="8212">, external BGP protocol requires explicit configuration
2468
of import and export policies (in contrast to other protocols, where default
2469
policies of <cf/import all/ and <cf/export none/ are used in absence of explicit
2470
configuration). Note that blanket policies like <cf/all/ or <cf/none/ can still
2471
be used in explicit configuration.
2472

    
2473
<p>BGP channels have additional config options (together with the common ones):
2474

    
2475
<descrip>
2476
	<tag><label id="bgp-next-hop-keep">next hop keep</tag>
2477
	Forward the received Next Hop attribute even in situations where the
2478
	local address should be used instead, like when the route is sent to an
2479
	interface with a different subnet. Default: disabled.
2480

    
2481
	<tag><label id="bgp-next-hop-self">next hop self</tag>
2482
	Avoid calculation of the Next Hop attribute and always advertise our own
2483
	source address as a next hop. This needs to be used only occasionally to
2484
	circumvent misconfigurations of other routers. Default: disabled.
2485

    
2486
	<tag><label id="bgp-next-hop-address">next hop address <m/ip/</tag>
2487
	Avoid calculation of the Next Hop attribute and always advertise this address
2488
	as a next hop.
2489

    
2490
	<tag><label id="bgp-missing-lladdr">missing lladdr self|drop|ignore</tag>
2491
	Next Hop attribute in BGP-IPv6 sometimes contains just the global IPv6
2492
	address, but sometimes it has to contain both global and link-local IPv6
2493
	addresses. This option specifies what to do if BIRD have to send both
2494
	addresses but does not know link-local address. This situation might
2495
	happen when routes from other protocols are exported to BGP, or when
2496
	improper updates are received from BGP peers. <cf/self/ means that BIRD
2497
	advertises its own local address instead. <cf/drop/ means that BIRD
2498
	skips that prefixes and logs error. <cf/ignore/ means that BIRD ignores
2499
	the problem and sends just the global address (and therefore forms
2500
	improper BGP update). Default: <cf/self/, unless BIRD is configured as a
2501
	route server (option <cf/rs client/), in that case default is <cf/ignore/,
2502
	because route servers usually do not forward packets themselves.
2503

    
2504
	<tag><label id="bgp-gateway">gateway direct|recursive</tag>
2505
	For received routes, their <cf/gw/ (immediate next hop) attribute is
2506
	computed from received <cf/bgp_next_hop/ attribute. This option
2507
	specifies how it is computed. Direct mode means that the IP address from
2508
	<cf/bgp_next_hop/ is used if it is directly reachable, otherwise the
2509
	neighbor IP address is used. Recursive mode means that the gateway is
2510
	computed by an IGP routing table lookup for the IP address from
2511
	<cf/bgp_next_hop/. Note that there is just one level of indirection in
2512
	recursive mode - the route obtained by the lookup must not be recursive
2513
	itself, to prevent mutually recursive routes.
2514

    
2515
	Recursive mode is the behavior specified by the BGP
2516
	standard. Direct mode is simpler, does not require any routes in a
2517
	routing table, and was used in older versions of BIRD, but does not
2518
	handle well nontrivial iBGP setups and multihop. Recursive mode is
2519
	incompatible with <ref id="dsc-table-sorted" name="sorted tables">. Default:
2520
	<cf/direct/ for direct sessions, <cf/recursive/ for multihop sessions.
2521

    
2522
	<tag><label id="bgp-igp-table">igp table <m/name/</tag>
2523
	Specifies a table that is used as an IGP routing table. The type of this
2524
	table must be as allowed in the table above. This option is allowed once
2525
	for every allowed table type. Default: the same as the main table
2526
	the channel is connected to (if eligible).
2527

    
2528
	<tag><label id="bgp-secondary">secondary <m/switch/</tag>
2529
	Usually, if an export filter rejects a selected route, no other route is
2530
	propagated for that network. This option allows to try the next route in
2531
	order until one that is accepted is found or all routes for that network
2532
	are rejected. This can be used for route servers that need to propagate
2533
	different tables to each client but do not want to have these tables
2534
	explicitly (to conserve memory). This option requires that the connected
2535
	routing table is <ref id="dsc-table-sorted" name="sorted">. Default: off.
2536

    
2537
	<tag><label id="bgp-add-paths">add paths <m/switch/|rx|tx</tag>
2538
	Standard BGP can propagate only one path (route) per destination network
2539
	(usually the selected one). This option controls the add-path protocol
2540
	extension, which allows to advertise any number of paths to a
2541
	destination. Note that to be active, add-path has to be enabled on both
2542
	sides of the BGP session, but it could be enabled separately for RX and
2543
	TX direction. When active, all available routes accepted by the export
2544
	filter are advertised to the neighbor. Default: off.
2545

    
2546
	<tag><label id="bgp-graceful-restart-c">graceful restart <m/switch/</tag>
2547
	Although BGP graceful restart is configured mainly by protocol-wide
2548
	<ref id="bgp-graceful-restart" name="options">, it is possible to
2549
	configure restarting role per AFI/SAFI pair by this channel option.
2550
	The option is ignored if graceful restart is disabled by protocol-wide
2551
	option. Default: off in aware mode, on in full mode.
2552
</descrip>
2553

    
2554
<sect1>Attributes
2555
<label id="bgp-attr">
2556

    
2557
<p>BGP defines several route attributes. Some of them (those marked with
2558
`<tt/I/' in the table below) are available on internal BGP connections only,
2559
some of them (marked with `<tt/O/') are optional.
2560

    
2561
<descrip>
2562
	<tag><label id="rta-bgp-path">bgppath bgp_path/</tag>
2563
	Sequence of AS numbers describing the AS path the packet will travel
2564
	through when forwarded according to the particular route. In case of
2565
	internal BGP it doesn't contain the number of the local AS.
2566

    
2567
	<tag><label id="rta-bgp-local-pref">int bgp_local_pref/ [I]</tag>
2568
	Local preference value used for selection among multiple BGP routes (see
2569
	the selection rules above). It's used as an additional metric which is
2570
	propagated through the whole local AS.
2571

    
2572
	<tag><label id="rta-bgp-med">int bgp_med/ [O]</tag>
2573
	The Multiple Exit Discriminator of the route is an optional attribute
2574
	which is used on external (inter-AS) links to convey to an adjacent AS
2575
	the optimal entry point into the local AS. The received attribute is
2576
	also propagated over internal BGP links. The attribute value is zeroed
2577
	when a route is exported to an external BGP instance to ensure that the
2578
	attribute received from a neighboring AS is not propagated to other
2579
	neighboring ASes. A new value might be set in the export filter of an
2580
	external BGP instance. See <rfc id="4451"> for further discussion of
2581
	BGP MED attribute.
2582

    
2583
	<tag><label id="rta-bgp-origin">enum bgp_origin/</tag>
2584
	Origin of the route: either <cf/ORIGIN_IGP/ if the route has originated
2585
	in an interior routing protocol or <cf/ORIGIN_EGP/ if it's been imported
2586
	from the <tt>EGP</tt> protocol (nowadays it seems to be obsolete) or
2587
	<cf/ORIGIN_INCOMPLETE/ if the origin is unknown.
2588

    
2589
	<tag><label id="rta-bgp-next-hop">ip bgp_next_hop/</tag>
2590
	Next hop to be used for forwarding of packets to this destination. On
2591
	internal BGP connections, it's an address of the originating router if
2592
	it's inside the local AS or a boundary router the packet will leave the
2593
	AS through if it's an exterior route, so each BGP speaker within the AS
2594
	has a chance to use the shortest interior path possible to this point.
2595

    
2596
	<tag><label id="rta-bgp-atomic-aggr">void bgp_atomic_aggr/ [O]</tag>
2597
	This is an optional attribute which carries no value, but the sole
2598
	presence of which indicates that the route has been aggregated from
2599
	multiple routes by some router on the path from the originator.
2600

    
2601
<!-- we don't handle aggregators right since they are of a very obscure type
2602
	<tag>bgp_aggregator</tag>
2603
-->
2604
	<tag><label id="rta-bgp-community">clist bgp_community/ [O]</tag>
2605
	List of community values associated with the route. Each such value is a
2606
	pair (represented as a <cf/pair/ data type inside the filters) of 16-bit
2607
	integers, the first of them containing the number of the AS which
2608
	defines the community and the second one being a per-AS identifier.
2609
	There are lots of uses of the community mechanism, but generally they
2610
	are used to carry policy information like "don't export to USA peers".
2611
	As each AS can define its own routing policy, it also has a complete
2612
	freedom about which community attributes it defines and what will their
2613
	semantics be.
2614

    
2615
	<tag><label id="rta-bgp-ext-community">eclist bgp_ext_community/ [O]</tag>
2616
	List of extended community values associated with the route. Extended
2617
	communities have similar usage as plain communities, but they have an
2618
	extended range (to allow 4B ASNs) and a nontrivial structure with a type
2619
	field. Individual community values are represented using an <cf/ec/ data
2620
	type inside the filters.
2621

    
2622
	<tag><label id="rta-bgp-large-community">lclist <cf/bgp_large_community/ [O]</tag>
2623
	List of large community values associated with the route. Large BGP
2624
	communities is another variant of communities, but contrary to extended
2625
	communities they behave very much the same way as regular communities,
2626
	just larger -- they are uniform untyped triplets of 32bit numbers.
2627
	Individual community values are represented using an <cf/lc/ data type
2628
	inside the filters.
2629

    
2630
	<tag><label id="rta-bgp-originator-id">quad bgp_originator_id/ [I, O]</tag>
2631
	This attribute is created by the route reflector when reflecting the
2632
	route and contains the router ID of the originator of the route in the
2633
	local AS.
2634

    
2635
	<tag><label id="rta-bgp-cluster-list">clist bgp_cluster_list/ [I, O]</tag>
2636
	This attribute contains a list of cluster IDs of route reflectors. Each
2637
	route reflector prepends its cluster ID when reflecting the route.
2638
</descrip>
2639

    
2640
<sect1>Example
2641
<label id="bgp-exam">
2642

    
2643
<p><code>
2644
protocol bgp {
2645
	local 198.51.100.14 as 65000;	     # Use a private AS number
2646
	neighbor 198.51.100.130 as 64496;    # Our neighbor ...
2647
	multihop;			     # ... which is connected indirectly
2648
	ipv4 {
2649
		export filter {			     # We use non-trivial export rules
2650
			if source = RTS_STATIC then { # Export only static routes
2651
				# Assign our community
2652
				bgp_community.add((65000,64501));
2653
				# Artificially increase path length
2654
				# by advertising local AS number twice
2655
				if bgp_path ~ [= 65000 =] then
2656
					bgp_path.prepend(65000);
2657
				accept;
2658
			}
2659
			reject;
2660
		};
2661
		import all;
2662
		next hop self; # advertise this router as next hop
2663
		igp table myigptable4; # IGP table for routes with IPv4 nexthops
2664
		igp table myigptable6; # IGP table for routes with IPv6 nexthops
2665
	};
2666
	ipv6 {
2667
		export filter mylargefilter; # We use a named filter
2668
		import all;
2669
		missing lladdr self;
2670
		igp table myigptable4; # IGP table for routes with IPv4 nexthops
2671
		igp table myigptable6; # IGP table for routes with IPv6 nexthops
2672
	};
2673
	ipv4 multicast {
2674
		import all;
2675
		export filter someotherfilter;
2676
		table mymulticasttable4; # Another IPv4 table, dedicated for multicast
2677
		igp table myigptable4;
2678
	};
2679
}
2680
</code>
2681

    
2682

    
2683
<sect>Device
2684
<label id="device">
2685

    
2686
<p>The Device protocol is not a real routing protocol. It doesn't generate any
2687
routes and it only serves as a module for getting information about network
2688
interfaces from the kernel. This protocol supports no channel.
2689

    
2690
<p>Except for very unusual circumstances, you probably should include this
2691
protocol in the configuration since almost all other protocols require network
2692
interfaces to be defined for them to work with.
2693

    
2694
<sect1>Configuration
2695
<label id="device-config">
2696

    
2697
<p><descrip>
2698
	<tag><label id="device-scan-time">scan time <m/number/</tag>
2699
	Time in seconds between two scans of the network interface list. On
2700
	systems where we are notified about interface status changes
2701
	asynchronously (such as newer versions of Linux), we need to scan the
2702
	list only in order to avoid confusion by lost notification messages,
2703
	so the default time is set to a large value.
2704

    
2705
	<tag><label id="device-iface">interface <m/pattern/ [, <m/.../]</tag>
2706

    
2707
	By default, the Device protocol handles all interfaces without any
2708
	configuration. Interface definitions allow to specify optional
2709
	parameters for specific interfaces. See <ref id="proto-iface"
2710
	name="interface"> common option for detailed description. Currently only
2711
	one interface option is available:
2712

    
2713
	<tag><label id="device-preferred">preferred <m/ip/</tag>
2714
	If a network interface has more than one IP address, BIRD chooses one of
2715
	them as a preferred one. Preferred IP address is used as source address
2716
	for packets or announced next hop by routing protocols. Precisely, BIRD
2717
	chooses one preferred IPv4 address, one preferred IPv6 address and one
2718
	preferred link-local IPv6 address. By default, BIRD chooses the first
2719
	found IP address as the preferred one.
2720

    
2721
	This option allows to specify which IP address should be preferred. May
2722
	be used multiple times for different address classes (IPv4, IPv6, IPv6
2723
	link-local). In all cases, an address marked by operating system as
2724
	secondary cannot be chosen as the primary one.
2725
</descrip>
2726

    
2727
<p>As the Device protocol doesn't generate any routes, it cannot have
2728
any attributes. Example configuration looks like this:
2729

    
2730
<p><code>
2731
protocol device {
2732
	scan time 10;		# Scan the interfaces often
2733
	interface "eth0" {
2734
		preferred 192.168.1.1;
2735
		preferred 2001:db8:1:10::1;
2736
	};
2737
}
2738
</code>
2739

    
2740

    
2741
<sect>Direct
2742
<label id="direct">
2743

    
2744
<p>The Direct protocol is a simple generator of device routes for all the
2745
directly connected networks according to the list of interfaces provided by the
2746
kernel via the Device protocol. The Direct protocol supports both IPv4 and IPv6
2747
channels.
2748

    
2749
<p>The question is whether it is a good idea to have such device routes in BIRD
2750
routing table. OS kernel usually handles device routes for directly connected
2751
networks by itself so we don't need (and don't want) to export these routes to
2752
the kernel protocol. OSPF protocol creates device routes for its interfaces
2753
itself and BGP protocol is usually used for exporting aggregate routes. Although
2754
there are some use cases that use the direct protocol (like abusing eBGP as an
2755
IGP routing protocol), in most cases it is not needed to have these device
2756
routes in BIRD routing table and to use the direct protocol.
2757

    
2758
<p>There is one notable case when you definitely want to use the direct protocol
2759
-- running BIRD on BSD systems. Having high priority device routes for directly
2760
connected networks from the direct protocol protects kernel device routes from
2761
being overwritten or removed by IGP routes during some transient network
2762
conditions, because a lower priority IGP route for the same network is not
2763
exported to the kernel routing table. This is an issue on BSD systems only, as
2764
on Linux systems BIRD cannot change non-BIRD route in the kernel routing table.
2765

    
2766
<p>There are just few configuration options for the Direct protocol:
2767

    
2768
<p><descrip>
2769
	<tag><label id="direct-iface">interface <m/pattern/ [, <m/.../]</tag>
2770
	By default, the Direct protocol will generate device routes for all the
2771
	interfaces available. If you want to restrict it to some subset of
2772
	interfaces or addresses (e.g. if you're using multiple routing tables
2773
	for policy routing and some of the policy domains don't contain all
2774
	interfaces), just use this clause. See <ref id="proto-iface" name="interface">
2775
	common option for detailed description. The Direct protocol uses
2776
	extended interface clauses.
2777

    
2778
	<tag><label id="direct-check-link">check link <m/switch/</tag>
2779
	If enabled, a hardware link state (reported by OS) is taken into
2780
	consideration. Routes for directly connected networks are generated only
2781
	if link up is reported and they are withdrawn when link disappears
2782
	(e.g., an ethernet cable is unplugged). Default value is no.
2783
</descrip>
2784

    
2785
<p>Direct device routes don't contain any specific attributes.
2786

    
2787
<p>Example config might look like this:
2788

    
2789
<p><code>
2790
protocol direct {
2791
	ipv4;
2792
	ipv6;
2793
	interface "-arc*", "*";		# Exclude the ARCnets
2794
}
2795
</code>
2796

    
2797

    
2798
<sect>Kernel
2799
<label id="krt">
2800

    
2801
<p>The Kernel protocol is not a real routing protocol. Instead of communicating
2802
with other routers in the network, it performs synchronization of BIRD's routing
2803
tables with the OS kernel. Basically, it sends all routing table updates to the
2804
kernel and from time to time it scans the kernel tables to see whether some
2805
routes have disappeared (for example due to unnoticed up/down transition of an
2806
interface) or whether an `alien' route has been added by someone else (depending
2807
on the <cf/learn/ switch, such routes are either ignored or accepted to our
2808
table).
2809

    
2810
<p>Unfortunately, there is one thing that makes the routing table synchronization
2811
a bit more complicated. In the kernel routing table there are also device routes
2812
for directly connected networks. These routes are usually managed by OS itself
2813
(as a part of IP address configuration) and we don't want to touch that. They
2814
are completely ignored during the scan of the kernel tables and also the export
2815
of device routes from BIRD tables to kernel routing tables is restricted to
2816
prevent accidental interference. This restriction can be disabled using
2817
<cf/device routes/ switch.
2818

    
2819
<p>If your OS supports only a single routing table, you can configure only one
2820
instance of the Kernel protocol. If it supports multiple tables (in order to
2821
allow policy routing; such an OS is for example Linux), you can run as many
2822
instances as you want, but each of them must be connected to a different BIRD
2823
routing table and to a different kernel table.
2824

    
2825
<p>Because the kernel protocol is partially integrated with the connected
2826
routing table, there are two limitations - it is not possible to connect more
2827
kernel protocols to the same routing table and changing route destination
2828
(gateway) in an export filter of a kernel protocol does not work. Both
2829
limitations can be overcome using another routing table and the pipe protocol.
2830

    
2831
<p>The Kernel protocol supports both IPv4 and IPv6 channels; only one of them
2832
can be configured in each protocol instance.
2833

    
2834
<sect1>Configuration
2835
<label id="krt-config">
2836

    
2837
<p><descrip>
2838
	<tag><label id="krt-persist">persist <m/switch/</tag>
2839
	Tell BIRD to leave all its routes in the routing tables when it exits
2840
	(instead of cleaning them up).
2841

    
2842
	<tag><label id="krt-scan-time">scan time <m/number/</tag>
2843
	Time in seconds between two consecutive scans of the kernel routing
2844
	table.
2845

    
2846
	<tag><label id="krt-learn">learn <m/switch/</tag>
2847
	Enable learning of routes added to the kernel routing tables by other
2848
	routing daemons or by the system administrator. This is possible only on
2849
	systems which support identification of route authorship.
2850

    
2851
	<tag><label id="krt-kernel-table">kernel table <m/number/</tag>
2852
	Select which kernel table should this particular instance of the Kernel
2853
	protocol work with. Available only on systems supporting multiple
2854
	routing tables.
2855

    
2856
	<tag><label id="krt-metric">metric <m/number/</tag> (Linux)
2857
	Use specified value as a kernel metric (priority) for all routes sent to
2858
	the kernel. When multiple routes for the same network are in the kernel
2859
	routing table, the Linux kernel chooses one with lower metric. Also,
2860
	routes with different metrics do not clash with each other, therefore
2861
	using dedicated metric value is a reliable way to avoid overwriting
2862
	routes from other sources (e.g. kernel device routes). Metric 0 has a
2863
	special meaning of undefined metric, in which either OS default is used,
2864
	or per-route metric can be set using <cf/krt_metric/ attribute. Default:
2865
	32.
2866

    
2867
	<tag><label id="krt-graceful-restart">graceful restart <m/switch/</tag>
2868
	Participate in graceful restart recovery. If this option is enabled and
2869
	a graceful restart recovery is active, the Kernel protocol will defer
2870
	synchronization of routing tables until the end of the recovery. Note
2871
	that import of kernel routes to BIRD is not affected.
2872

    
2873
	<tag><label id="krt-merge-paths">merge paths <M>switch</M> [limit <M>number</M>]</tag>
2874
	Usually, only best routes are exported to the kernel protocol. With path
2875
	merging enabled, both best routes and equivalent non-best routes are
2876
	merged during export to generate one ECMP (equal-cost multipath) route
2877
	for each network. This is useful e.g. for BGP multipath. Note that best
2878
	routes are still pivotal for route export (responsible for most
2879
	properties of resulting ECMP routes), while exported non-best routes are
2880
	responsible just for additional multipath next hops. This option also
2881
	allows to specify a limit on maximal number of nexthops in one route. By
2882
	default, multipath merging is disabled. If enabled, default value of the
2883
	limit is 16.
2884
</descrip>
2885

    
2886
<sect1>Attributes
2887
<label id="krt-attr">
2888

    
2889
<p>The Kernel protocol defines several attributes. These attributes are
2890
translated to appropriate system (and OS-specific) route attributes. We support
2891
these attributes:
2892

    
2893
<descrip>
2894
	<tag><label id="rta-krt-source">int krt_source/</tag>
2895
	The original source of the imported kernel route. The value is
2896
	system-dependent. On Linux, it is a value of the protocol field of the
2897
	route. See /etc/iproute2/rt_protos for common values. On BSD, it is
2898
	based on STATIC and PROTOx flags. The attribute is read-only.
2899

    
2900
	<tag><label id="rta-krt-metric">int krt_metric/</tag> (Linux)
2901
	The kernel metric of the route. When multiple same routes are in a
2902
	kernel routing table, the Linux kernel chooses one with lower metric.
2903
	Note that preferred way to set kernel metric is to use protocol option
2904
	<cf/metric/, unless per-route metric values are needed.
2905

    
2906
	<tag><label id="rta-krt-prefsrc">ip krt_prefsrc/</tag> (Linux)
2907
	The preferred source address. Used in source address selection for
2908
	outgoing packets. Has to be one of the IP addresses of the router.
2909

    
2910
	<tag><label id="rta-krt-realm">int krt_realm/</tag> (Linux)
2911
	The realm of the route. Can be used for traffic classification.
2912

    
2913
	<tag><label id="rta-krt-scope">int krt_scope/</tag> (Linux IPv4)
2914
	The scope of the route. Valid values are 0-254, although Linux kernel
2915
	may reject some values depending on route type and nexthop. It is
2916
	supposed to represent `indirectness' of the route, where nexthops of
2917
	routes are resolved through routes with a higher scope, but in current
2918
	kernels anything below <it/link/ (253) is treated as <it/global/ (0).
2919
	When not present, global scope is implied for all routes except device
2920
	routes, where link scope is used by default.
2921
</descrip>
2922

    
2923
<p>In Linux, there is also a plenty of obscure route attributes mostly focused
2924
on tuning TCP performance of local connections. BIRD supports most of these
2925
attributes, see Linux or iproute2 documentation for their meaning. Attributes
2926
<cf/krt_lock_*/ and <cf/krt_feature_*/ have type bool, others have type int.
2927
Supported attributes are:
2928

    
2929
<cf/krt_mtu/, <cf/krt_lock_mtu/, <cf/krt_window/, <cf/krt_lock_window/,
2930
<cf/krt_rtt/, <cf/krt_lock_rtt/, <cf/krt_rttvar/, <cf/krt_lock_rttvar/,
2931
<cf/krt_sstresh/, <cf/krt_lock_sstresh/, <cf/krt_cwnd/, <cf/krt_lock_cwnd/,
2932
<cf/krt_advmss/, <cf/krt_lock_advmss/, <cf/krt_reordering/, <cf/krt_lock_reordering/,
2933
<cf/krt_hoplimit/, <cf/krt_lock_hoplimit/, <cf/krt_rto_min/, <cf/krt_lock_rto_min/,
2934
<cf/krt_initcwnd/, <cf/krt_initrwnd/, <cf/krt_quickack/,
2935
<cf/krt_feature_ecn/, <cf/krt_feature_allfrag/
2936

    
2937
<sect1>Example
2938
<label id="krt-exam">
2939

    
2940
<p>A simple configuration can look this way:
2941

    
2942
<p><code>
2943
protocol kernel {
2944
	export all;
2945
}
2946
</code>
2947

    
2948
<p>Or for a system with two routing tables:
2949

    
2950
<p><code>
2951
protocol kernel {		# Primary routing table
2952
	learn;			# Learn alien routes from the kernel
2953
	persist;		# Don't remove routes on bird shutdown
2954
	scan time 10;		# Scan kernel routing table every 10 seconds
2955
	ipv4 {
2956
		import all;
2957
		export all;
2958
	};
2959
}
2960

    
2961
protocol kernel {		# Secondary routing table
2962
	kernel table 100;
2963
	ipv4 {
2964
		table auxtable;
2965
		export all;
2966
	};
2967
}
2968
</code>
2969

    
2970

    
2971
<sect>OSPF
2972
<label id="ospf">
2973

    
2974
<sect1>Introduction
2975
<label id="ospf-intro">
2976

    
2977
<p>Open Shortest Path First (OSPF) is a quite complex interior gateway
2978
protocol. The current IPv4 version (OSPFv2) is defined in <rfc id="2328"> and
2979
the current IPv6 version (OSPFv3) is defined in <rfc id="5340"> It's a link
2980
state (a.k.a. shortest path first) protocol -- each router maintains a database
2981
describing the autonomous system's topology. Each participating router has an
2982
identical copy of the database and all routers run the same algorithm
2983
calculating a shortest path tree with themselves as a root. OSPF chooses the
2984
least cost path as the best path.
2985

    
2986
<p>In OSPF, the autonomous system can be split to several areas in order to
2987
reduce the amount of resources consumed for exchanging the routing information
2988
and to protect the other areas from incorrect routing data. Topology of the area
2989
is hidden to the rest of the autonomous system.
2990

    
2991
<p>Another very important feature of OSPF is that it can keep routing information
2992
from other protocols (like Static or BGP) in its link state database as external
2993
routes. Each external route can be tagged by the advertising router, making it
2994
possible to pass additional information between routers on the boundary of the
2995
autonomous system.
2996

    
2997
<p>OSPF quickly detects topological changes in the autonomous system (such as
2998
router interface failures) and calculates new loop-free routes after a short
2999
period of convergence. Only a minimal amount of routing traffic is involved.
3000

    
3001
<p>Each router participating in OSPF routing periodically sends Hello messages
3002
to all its interfaces. This allows neighbors to be discovered dynamically. Then
3003
the neighbors exchange theirs parts of the link state database and keep it
3004
identical by flooding updates. The flooding process is reliable and ensures that
3005
each router detects all changes.
3006

    
3007
<sect1>Configuration
3008
<label id="ospf-config">
3009

    
3010
<p>First, the desired OSPF version can be specified by using <cf/ospf v2/ or
3011
<cf/ospf v3/ as a protocol type. By default, OSPFv2 is used. In the main part of
3012
configuration, there can be multiple definitions of OSPF areas, each with a
3013
different id. These definitions includes many other switches and multiple
3014
definitions of interfaces. Definition of interface may contain many switches and
3015
constant definitions and list of neighbors on nonbroadcast networks.
3016

    
3017
<p>OSPFv2 needs one IPv4 channel. OSPFv3 needs either one IPv6 channel, or one
3018
IPv4 channel (<rfc id="5838">). Therefore, it is possible to use OSPFv3 for both
3019
IPv4 and Pv6 routing, but it is necessary to have two protocol instances anyway.
3020
If no channel is configured, appropriate channel is defined with default
3021
parameters.
3022

    
3023
<code>
3024
protocol ospf [v2|v3] &lt;name&gt; {
3025
	rfc1583compat &lt;switch&gt;;
3026
	rfc5838 &lt;switch&gt;;
3027
	instance id &lt;num&gt;;
3028
	stub router &lt;switch&gt;;
3029
	tick &lt;num&gt;;
3030
	ecmp &lt;switch&gt; [limit &lt;num&gt;];
3031
	merge external &lt;switch&gt;;
3032
	area &lt;id&gt; {
3033
		stub;
3034
		nssa;
3035
		summary &lt;switch&gt;;
3036
		default nssa &lt;switch&gt;;
3037
		default cost &lt;num&gt;;
3038
		default cost2 &lt;num&gt;;
3039
		translator &lt;switch&gt;;
3040
		translator stability &lt;num&gt;;
3041

    
3042
                networks {
3043
			&lt;prefix&gt;;
3044
			&lt;prefix&gt; hidden;
3045
		}
3046
                external {
3047
			&lt;prefix&gt;;
3048
			&lt;prefix&gt; hidden;
3049
			&lt;prefix&gt; tag &lt;num&gt;;
3050
		}
3051
		stubnet &lt;prefix&gt;;
3052
		stubnet &lt;prefix&gt; {
3053
			hidden &lt;switch&gt;;
3054
			summary &lt;switch&gt;;
3055
			cost &lt;num&gt;;
3056
		}
3057
		interface &lt;interface pattern&gt; [instance &lt;num&gt;] {
3058
			cost &lt;num&gt;;
3059
			stub &lt;switch&gt;;
3060
			hello &lt;num&gt;;
3061
			poll &lt;num&gt;;
3062
			retransmit &lt;num&gt;;
3063
			priority &lt;num&gt;;
3064
			wait &lt;num&gt;;
3065
			dead count &lt;num&gt;;
3066
			dead &lt;num&gt;;
3067
			secondary &lt;switch&gt;;
3068
			rx buffer [normal|large|&lt;num&gt;];
3069
			tx length &lt;num&gt;;
3070
			type [broadcast|bcast|pointopoint|ptp|
3071
				nonbroadcast|nbma|pointomultipoint|ptmp];
3072
			link lsa suppression &lt;switch&gt;;
3073
			strict nonbroadcast &lt;switch&gt;;
3074
			real broadcast &lt;switch&gt;;
3075
			ptp netmask &lt;switch&gt;;
3076
			check link &lt;switch&gt;;
3077
			bfd &lt;switch&gt;;
3078
			ecmp weight &lt;num&gt;;
3079
			ttl security [&lt;switch&gt;; | tx only]
3080
			tx class|dscp &lt;num&gt;;
3081
			tx priority &lt;num&gt;;
3082
			authentication none|simple|cryptographic;
3083
			password "&lt;text&gt;";
3084
			password "&lt;text&gt;" {
3085
				id &lt;num&gt;;
3086
				generate from "&lt;date&gt;";
3087
				generate to "&lt;date&gt;";
3088
				accept from "&lt;date&gt;";
3089
				accept to "&lt;date&gt;";
3090
				from "&lt;date&gt;";
3091
				to "&lt;date&gt;";
3092
				algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
3093
			};
3094
			neighbors {
3095
				&lt;ip&gt;;
3096
				&lt;ip&gt; eligible;
3097
			};
3098
		};
3099
		virtual link &lt;id&gt; [instance &lt;num&gt;] {
3100
			hello &lt;num&gt;;
3101
			retransmit &lt;num&gt;;
3102
			wait &lt;num&gt;;
3103
			dead count &lt;num&gt;;
3104
			dead &lt;num&gt;;
3105
			authentication none|simple|cryptographic;
3106
			password "&lt;text&gt;";
3107
			password "&lt;text&gt;" {
3108
				id &lt;num&gt;;
3109
				generate from "&lt;date&gt;";
3110
				generate to "&lt;date&gt;";
3111
				accept from "&lt;date&gt;";
3112
				accept to "&lt;date&gt;";
3113
				from "&lt;date&gt;";
3114
				to "&lt;date&gt;";
3115
				algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
3116
			};
3117
		};
3118
	};
3119
}
3120
</code>
3121

    
3122
<descrip>
3123
	<tag><label id="ospf-rfc1583compat">rfc1583compat <M>switch</M></tag>
3124
	This option controls compatibility of routing table calculation with
3125
	<rfc id="1583">. Default value is no.
3126

    
3127
	<tag><label id="ospf-rfc5838">rfc5838 <m/switch/</tag>
3128
	Basic OSPFv3 is limited to IPv6 unicast routing. The <rfc id="5838">
3129
	extension defines support for more address families (IPv4, IPv6, both
3130
	unicast and multicast). The extension is enabled by default, but can be
3131
	disabled if necessary, as it restricts the range of available instance
3132
	IDs. Default value is yes.
3133

    
3134
	<tag><label id="ospf-instance-id">instance id <m/num/</tag>
3135
	When multiple OSPF protocol instances are active on the same links, they
3136
	should use different instance IDs to distinguish their packets. Although
3137
	it could be done on per-interface basis, it is often preferred to set
3138
	one instance ID to whole OSPF domain/topology (e.g., when multiple
3139
	instances are used to represent separate logical topologies on the same
3140
	physical network). This option specifies the instance ID for all
3141
	interfaces of the OSPF instance, but can be overridden by
3142
	<cf/interface/ option. Default value is 0 unless OSPFv3-AF extended
3143
	address families are used, see <rfc id="5838"> for that case.
3144

    
3145
	<tag><label id="ospf-stub-router">stub router <M>switch</M></tag>
3146
	This option configures the router to be a stub router, i.e., a router
3147
	that participates in the OSPF topology but does not allow transit
3148
	traffic. In OSPFv2, this is implemented by advertising maximum metric
3149
	for outgoing links. In OSPFv3, the stub router behavior is announced by
3150
	clearing the R-bit in the router LSA. See <rfc id="6987"> for details.
3151
	Default value is no.
3152

    
3153
	<tag><label id="ospf-tick">tick <M>num</M></tag>
3154
	The routing table calculation and clean-up of areas' databases is not
3155
	performed when a single link state change arrives. To lower the CPU
3156
	utilization, it's processed later at periodical intervals of <m/num/
3157
	seconds. The default value is 1.
3158

    
3159
	<tag><label id="ospf-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
3160
	This option specifies whether OSPF is allowed to generate ECMP
3161
	(equal-cost multipath) routes. Such routes are used when there are
3162
	several directions to the destination, each with the same (computed)
3163
	cost. This option also allows to specify a limit on maximum number of
3164
	nexthops in one route. By default, ECMP is enabled if supported by
3165
	Kernel. Default value of the limit is 16.
3166

    
3167
	<tag><label id="ospf-merge-external">merge external <M>switch</M></tag>
3168
	This option specifies whether OSPF should merge external routes from
3169
	different routers/LSAs for the same destination. When enabled together
3170
	with <cf/ecmp/, equal-cost external routes will be combined to multipath
3171
	routes in the same way as regular routes. When disabled, external routes
3172
	from different LSAs are treated as separate even if they represents the
3173
	same destination. Default value is no.
3174

    
3175
	<tag><label id="ospf-area">area <M>id</M></tag>
3176
	This defines an OSPF area with given area ID (an integer or an IPv4
3177
	address, similarly to a router ID). The most important area is the
3178
	backbone (ID 0) to which every other area must be connected.
3179

    
3180
	<tag><label id="ospf-stub">stub</tag>
3181
	This option configures the area to be a stub area. External routes are
3182
	not flooded into stub areas. Also summary LSAs can be limited in stub
3183
	areas (see option <cf/summary/). By default, the area is not a stub
3184
	area.
3185

    
3186
	<tag><label id="ospf-nssa">nssa</tag>
3187
	This option configures the area to be a NSSA (Not-So-Stubby Area). NSSA
3188
	is a variant of a stub area which allows a limited way of external route
3189
	propagation. Global external routes are not propagated into a NSSA, but
3190
	an external route can be imported into NSSA as a (area-wide) NSSA-LSA
3191
	(and possibly translated and/or aggregated on area boundary). By
3192
	default, the area is not NSSA.
3193

    
3194
	<tag><label id="ospf-summary">summary <M>switch</M></tag>
3195
	This option controls propagation of summary LSAs into stub or NSSA
3196
	areas. If enabled, summary LSAs are propagated as usual, otherwise just
3197
	the default summary route (0.0.0.0/0) is propagated (this is sometimes
3198
	called totally stubby area). If a stub area has more area boundary
3199
	routers, propagating summary LSAs could lead to more efficient routing
3200
	at the cost of larger link state database. Default value is no.
3201

    
3202
	<tag><label id="ospf-default-nssa">default nssa <M>switch</M></tag>
3203
	When <cf/summary/ option is enabled, default summary route is no longer
3204
	propagated to the NSSA. In that case, this option allows to originate
3205
	default route as NSSA-LSA to the NSSA. Default value is no.
3206

    
3207
	<tag><label id="ospf-default-cost">default cost <M>num</M></tag>
3208
	This option controls the cost of a default route propagated to stub and
3209
	NSSA areas. Default value is 1000.
3210

    
3211
	<tag><label id="ospf-default-cost2">default cost2 <M>num</M></tag>
3212
	When a default route is originated as NSSA-LSA, its cost can use either
3213
	type 1 or type 2 metric. This option allows to specify the cost of a
3214
	default route in type 2 metric. By default, type 1 metric (option
3215
	<cf/default cost/) is used.
3216

    
3217
	<tag><label id="ospf-translator">translator <M>switch</M></tag>
3218
	This option controls translation of NSSA-LSAs into external LSAs. By
3219
	default, one translator per NSSA is automatically elected from area
3220
	boundary routers. If enabled, this area boundary router would
3221
	unconditionally translate all NSSA-LSAs regardless of translator
3222
	election. Default value is no.
3223

    
3224
	<tag><label id="ospf-translator-stability">translator stability <M>num</M></tag>
3225
	This option controls the translator stability interval (in seconds).
3226
	When the new translator is elected, the old one keeps translating until
3227
	the interval is over. Default value is 40.
3228

    
3229
	<tag><label id="ospf-networks">networks { <m/set/ }</tag>
3230
	Definition of area IP ranges. This is used in summary LSA origination.
3231
	Hidden networks are not propagated into other areas.
3232

    
3233
	<tag><label id="ospf-external">external { <m/set/ }</tag>
3234
	Definition of external area IP ranges for NSSAs. This is used for
3235
	NSSA-LSA translation. Hidden networks are not translated into external
3236
	LSAs. Networks can have configured route tag.
3237

    
3238
	<tag><label id="ospf-stubnet">stubnet <m/prefix/ { <m/options/ }</tag>
3239
	Stub networks are networks that are not transit networks between OSPF
3240
	routers. They are also propagated through an OSPF area as a part of a
3241
	link state database. By default, BIRD generates a stub network record
3242
	for each primary network address on each OSPF interface that does not
3243
	have any OSPF neighbors, and also for each non-primary network address
3244
	on each OSPF interface. This option allows to alter a set of stub
3245
	networks propagated by this router.
3246

    
3247
	Each instance of this option adds a stub network with given network
3248
	prefix to the set of propagated stub network, unless option <cf/hidden/
3249
	is used. It also suppresses default stub networks for given network
3250
	prefix. When option <cf/summary/ is used, also default stub networks
3251
	that are subnetworks of given stub network are suppressed. This might be
3252
	used, for example, to aggregate generated stub networks.
3253

    
3254
	<tag><label id="ospf-iface">interface <M>pattern</M> [instance <m/num/]</tag>
3255
	Defines that the specified interfaces belong to the area being defined.
3256
	See <ref id="proto-iface" name="interface"> common option for detailed
3257
	description. In OSPFv2, extended interface clauses are used, because
3258
	each network prefix is handled as a separate virtual interface.
3259

    
3260
	You can specify alternative instance ID for the interface definition,
3261
	therefore it is possible to have several instances of that interface
3262
	with different options or even in different areas. For OSPFv2, instance
3263
	ID support is an extension (<rfc id="6549">) and is supposed to be set
3264
	per-protocol. For OSPFv3, it is an integral feature.
3265

    
3266
	<tag><label id="ospf-virtual-link">virtual link <M>id</M> [instance <m/num/]</tag>
3267
	Virtual link to router with the router id. Virtual link acts as a
3268
	point-to-point interface belonging to backbone. The actual area is used
3269
	as a transport area. This item cannot be in the backbone. Like with
3270
	<cf/interface/ option, you could also use several virtual links to one
3271
	destination with different instance IDs.
3272

    
3273
	<tag><label id="ospf-cost">cost <M>num</M></tag>
3274
	Specifies output cost (metric) of an interface. Default value is 10.
3275

    
3276
	<tag><label id="ospf-stub-iface">stub <M>switch</M></tag>
3277
	If set to interface it does not listen to any packet and does not send
3278
	any hello. Default value is no.
3279

    
3280
	<tag><label id="ospf-hello">hello <M>num</M></tag>
3281
	Specifies interval in seconds between sending of Hello messages. Beware,
3282
	all routers on the same network need to have the same hello interval.
3283
	Default value is 10.
3284

    
3285
	<tag><label id="ospf-poll">poll <M>num</M></tag>
3286
	Specifies interval in seconds between sending of Hello messages for some
3287
	neighbors on NBMA network. Default value is 20.
3288

    
3289
	<tag><label id="ospf-retransmit">retransmit <M>num</M></tag>
3290
	Specifies interval in seconds between retransmissions of unacknowledged
3291
	updates. Default value is 5.
3292

    
3293
	<tag><label id="ospf-priority">priority <M>num</M></tag>
3294
	On every multiple access network (e.g., the Ethernet) Designated Router
3295
	and Backup Designated router are elected. These routers have some special
3296
	functions in the flooding process. Higher priority increases preferences
3297
	in this election. Routers with priority 0 are not eligible. Default
3298
	value is 1.
3299

    
3300
	<tag><label id="ospf-wait">wait <M>num</M></tag>
3301
	After start, router waits for the specified number of seconds between
3302
	starting election and building adjacency. Default value is 4*<m/hello/.
3303

    
3304
	<tag><label id="ospf-dead-count">dead count <M>num</M></tag>
3305
	When the router does not receive any messages from a neighbor in
3306
	<m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
3307

    
3308
	<tag><label id="ospf-dead">dead <M>num</M></tag>
3309
	When the router does not receive any messages from a neighbor in
3310
	<m/dead/ seconds, it will consider the neighbor down. If both directives
3311
	<cf/dead count/ and <cf/dead/ are used, <cf/dead/ has precedence.
3312

    
3313
	<tag><label id="ospf-secondary">secondary <M>switch</M></tag>
3314
	On BSD systems, older versions of BIRD supported OSPFv2 only for the
3315
	primary IP address of an interface, other IP ranges on the interface
3316
	were handled as stub networks. Since v1.4.1, regular operation on
3317
	secondary IP addresses is supported, but disabled by default for
3318
	compatibility. This option allows to enable it. The option is a
3319
	transitional measure, will be removed in the next major release as the
3320
	behavior will be changed. On Linux systems, the option is irrelevant, as
3321
	operation on non-primary addresses is already the regular behavior.
3322

    
3323
	<tag><label id="ospf-rx-buffer">rx buffer <M>num</M></tag>
3324
	This option allows to specify the size of buffers used for packet
3325
	processing. The buffer size should be bigger than maximal size of any
3326
	packets. By default, buffers are dynamically resized as needed, but a
3327
	fixed value could be specified. Value <cf/large/ means maximal allowed
3328
	packet size - 65535.
3329

    
3330
	<tag><label id="ospf-tx-length">tx length <M>num</M></tag>
3331
	Transmitted OSPF messages that contain large amount of information are
3332
	segmented to separate OSPF packets to avoid IP fragmentation. This
3333
	option specifies the soft ceiling for the length of generated OSPF
3334
	packets. Default value is the MTU of the network interface. Note that
3335
	larger OSPF packets may still be generated if underlying OSPF messages
3336
	cannot be splitted (e.g. when one large LSA is propagated).
3337

    
3338
	<tag><label id="ospf-type-bcast">type broadcast|bcast</tag>
3339
	BIRD detects a type of a connected network automatically, but sometimes
3340
	it's convenient to force use of a different type manually. On broadcast
3341
	networks (like ethernet), flooding and Hello messages are sent using
3342
	multicasts (a single packet for all the neighbors). A designated router
3343
	is elected and it is responsible for synchronizing the link-state
3344
	databases and originating network LSAs. This network type cannot be used
3345
	on physically NBMA networks and on unnumbered networks (networks without
3346
	proper IP prefix).
3347

    
3348
	<tag><label id="ospf-type-ptp">type pointopoint|ptp</tag>
3349
	Point-to-point networks connect just 2 routers together. No election is
3350
	performed and no network LSA is originated, which makes it simpler and
3351
	faster to establish. This network type is useful not only for physically
3352
	PtP ifaces (like PPP or tunnels), but also for broadcast networks used
3353
	as PtP links. This network type cannot be used on physically NBMA
3354
	networks.
3355

    
3356
	<tag><label id="ospf-type-nbma">type nonbroadcast|nbma</tag>
3357
	On NBMA networks, the packets are sent to each neighbor separately
3358
	because of lack of multicast capabilities. Like on broadcast networks,
3359
	a designated router is elected, which plays a central role in propagation
3360
	of LSAs. This network type cannot be used on unnumbered networks.
3361

    
3362
	<tag><label id="ospf-type-ptmp">type pointomultipoint|ptmp</tag>
3363
	This is another network type designed to handle NBMA networks. In this
3364
	case the NBMA network is treated as a collection of PtP links. This is
3365
	useful if not every pair of routers on the NBMA network has direct
3366
	communication, or if the NBMA network is used as an (possibly
3367
	unnumbered) PtP link.
3368

    
3369
	<tag><label id="ospf-link-lsa-suppression">link lsa suppression <m/switch/</tag>
3370
	In OSPFv3, link LSAs are generated for each link, announcing link-local
3371
	IPv6 address of the router to its local neighbors. These are useless on
3372
	PtP or PtMP networks and this option allows to suppress the link LSA
3373
	origination for such interfaces. The option is ignored on other than PtP
3374
	or PtMP interfaces. Default value is no.
3375

    
3376
	<tag><label id="ospf-strict-nonbroadcast">strict nonbroadcast <m/switch/</tag>
3377
	If set, don't send hello to any undefined neighbor. This switch is
3378
	ignored on other than NBMA or PtMP interfaces. Default value is no.
3379

    
3380
	<tag><label id="ospf-real-broadcast">real broadcast <m/switch/</tag>
3381
	In <cf/type broadcast/ or <cf/type ptp/ network configuration, OSPF
3382
	packets are sent as IP multicast packets. This option changes the
3383
	behavior to using old-fashioned IP broadcast packets. This may be useful
3384
	as a workaround if IP multicast for some reason does not work or does
3385
	not work reliably. This is a non-standard option and probably is not
3386
	interoperable with other OSPF implementations. Default value is no.
3387

    
3388
	<tag><label id="ospf-ptp-netmask">ptp netmask <m/switch/</tag>
3389
	In <cf/type ptp/ network configurations, OSPFv2 implementations should
3390
	ignore received netmask field in hello packets and should send hello
3391
	packets with zero netmask field on unnumbered PtP links. But some OSPFv2
3392
	implementations perform netmask checking even for PtP links. This option
3393
	specifies whether real netmask will be used in hello packets on <cf/type
3394
 	ptp/ interfaces. You should ignore this option unless you meet some
3395
	compatibility problems related to this issue. Default value is no for
3396
	unnumbered PtP links, yes otherwise.
3397

    
3398
	<tag><label id="ospf-check-link">check link <M>switch</M></tag>
3399
	If set, a hardware link state (reported by OS) is taken into consideration.
3400
	When a link disappears (e.g. an ethernet cable is unplugged), neighbors
3401
	are immediately considered unreachable and only the address of the iface
3402
	(instead of whole network prefix) is propagated. It is possible that
3403
	some hardware drivers or platforms do not implement this feature.
3404
	Default value is yes.
3405

    
3406
	<tag><label id="ospf-bfd">bfd <M>switch</M></tag>
3407
	OSPF could use BFD protocol as an advisory mechanism for neighbor
3408
	liveness and failure detection. If enabled, BIRD setups a BFD session
3409
	for each OSPF neighbor and tracks its liveness by it. This has an
3410
	advantage of an order of magnitude lower detection times in case of
3411
	failure. Note that BFD protocol also has to be configured, see
3412
	<ref id="bfd" name="BFD"> section for details. Default value is no.
3413

    
3414
	<tag><label id="ospf-ttl-security">ttl security [<m/switch/ | tx only]</tag>
3415
	TTL security is a feature that protects routing protocols from remote
3416
	spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
3417
	destined to neighbors. Because TTL is decremented when packets are
3418
	forwarded, it is non-trivial to spoof packets with TTL 255 from remote
3419
	locations. Note that this option would interfere with OSPF virtual
3420
	links.
3421

    
3422
	If this option is enabled, the router will send OSPF packets with TTL
3423
	255 and drop received packets with TTL less than 255. If this option si
3424
	set to <cf/tx only/, TTL 255 is used for sent packets, but is not
3425
	checked for received packets. Default value is no.
3426

    
3427
	<tag><label id="ospf-tx-class">tx class|dscp|priority <m/num/</tag>
3428
	These options specify the ToS/DiffServ/Traffic class/Priority of the
3429
	outgoing OSPF packets. See <ref id="proto-tx-class" name="tx class"> common
3430
	option for detailed description.
3431

    
3432
	<tag><label id="ospf-ecmp-weight">ecmp weight <M>num</M></tag>
3433
	When ECMP (multipath) routes are allowed, this value specifies a
3434
	relative weight used for nexthops going through the iface. Allowed
3435
	values are 1-256. Default value is 1.
3436

    
3437
	<tag><label id="ospf-auth-none">authentication none</tag>
3438
	No passwords are sent in OSPF packets. This is the default value.
3439

    
3440
	<tag><label id="ospf-auth-simple">authentication simple</tag>
3441
	Every packet carries 8 bytes of password. Received packets lacking this
3442
	password are ignored. This authentication mechanism is very weak.
3443
	This option is not available in OSPFv3.
3444

    
3445
	<tag><label id="ospf-auth-cryptographic">authentication cryptographic</tag>
3446
	An authentication code is appended to every packet. The specific
3447
	cryptographic algorithm is selected by option <cf/algorithm/ for each
3448
	key. The default cryptographic algorithm for OSPFv2 keys is Keyed-MD5
3449
	and for OSPFv3 keys is HMAC-SHA-256. Passwords are not sent open via
3450
	network, so this mechanism is quite secure. Packets can still be read by
3451
	an attacker.
3452

    
3453
	<tag><label id="ospf-pass">password "<M>text</M>"</tag>
3454
	Specifies a password used for authentication. See
3455
	<ref id="proto-pass" name="password"> common option for detailed
3456
	description.
3457

    
3458
	<tag><label id="ospf-neighbors">neighbors { <m/set/ } </tag>
3459
	A set of neighbors to which Hello messages on NBMA or PtMP networks are
3460
	to be sent. For NBMA networks, some of them could be marked as eligible.
3461
	In OSPFv3, link-local addresses should be used, using global ones is
3462
	possible, but it is nonstandard and might be problematic. And definitely,
3463
	link-local and global addresses should not be mixed.
3464
</descrip>
3465

    
3466
<sect1>Attributes
3467
<label id="ospf-attr">
3468

    
3469
<p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
3470

    
3471
<p>Metric is ranging from 1 to infinity (65535). External routes use
3472
<cf/metric type 1/ or <cf/metric type 2/. A <cf/metric of type 1/ is comparable
3473
with internal <cf/metric/, a <cf/metric of type 2/ is always longer than any
3474
<cf/metric of type 1/ or any <cf/internal metric/. <cf/Internal metric/ or
3475
<cf/metric of type 1/ is stored in attribute <cf/ospf_metric1/, <cf/metric type
3476
2/ is stored in attribute <cf/ospf_metric2/. If you specify both metrics only
3477
metric1 is used.
3478

    
3479
<p>Each external route can also carry attribute <cf/ospf_tag/ which is a 32-bit
3480
integer which is used when exporting routes to other protocols; otherwise, it
3481
doesn't affect routing inside the OSPF domain at all. The fourth attribute
3482
<cf/ospf_router_id/ is a router ID of the router advertising that route /
3483
network. This attribute is read-only. Default is <cf/ospf_metric2 = 10000/ and
3484
<cf/ospf_tag = 0/.
3485

    
3486
<sect1>Example
3487
<label id="ospf-exam">
3488

    
3489
<p><code>
3490
protocol ospf MyOSPF {
3491
	ipv4 {
3492
		export filter {
3493
			if source = RTS_BGP then {
3494
				ospf_metric1 = 100;
3495
				accept;
3496
			}
3497
			reject;
3498
		};
3499
	};
3500
	area 0.0.0.0 {
3501
		interface "eth*" {
3502
			cost 11;
3503
			hello 15;
3504
			priority 100;
3505
			retransmit 7;
3506
			authentication simple;
3507
			password "aaa";
3508
		};
3509
		interface "ppp*" {
3510
			cost 100;
3511
			authentication cryptographic;
3512
			password "abc" {
3513
				id 1;
3514
				generate to "22-04-2003 11:00:06";
3515
				accept from "17-01-2001 12:01:05";
3516
				algorithm hmac sha384;
3517
			};
3518
			password "def" {
3519
				id 2;
3520
				generate to "22-07-2005 17:03:21";
3521
				accept from "22-02-2001 11:34:06";
3522
				algorithm hmac sha512;
3523
			};
3524
		};
3525
		interface "arc0" {
3526
			cost 10;
3527
			stub yes;
3528
		};
3529
		interface "arc1";
3530
	};
3531
	area 120 {
3532
		stub yes;
3533
		networks {
3534
			172.16.1.0/24;
3535
			172.16.2.0/24 hidden;
3536
		}
3537
		interface "-arc0" , "arc*" {
3538
			type nonbroadcast;
3539
			authentication none;
3540
			strict nonbroadcast yes;
3541
			wait 120;
3542
			poll 40;
3543
			dead count 8;
3544
			neighbors {
3545
				192.168.120.1 eligible;
3546
				192.168.120.2;
3547
				192.168.120.10;
3548
			};
3549
		};
3550
	};
3551
}
3552
</code>
3553

    
3554

    
3555
<sect>Pipe
3556
<label id="pipe">
3557

    
3558
<sect1>Introduction
3559
<label id="pipe-intro">
3560

    
3561
<p>The Pipe protocol serves as a link between two routing tables, allowing
3562
routes to be passed from a table declared as primary (i.e., the one the pipe is
3563
connected to using the <cf/table/ configuration keyword) to the secondary one
3564
(declared using <cf/peer table/) and vice versa, depending on what's allowed by
3565
the filters. Export filters control export of routes from the primary table to
3566
the secondary one, import filters control the opposite direction. Both tables
3567
must be of the same nettype.
3568

    
3569
<p>The Pipe protocol may work in the transparent mode mode or in the opaque
3570
mode. In the transparent mode, the Pipe protocol retransmits all routes from
3571
one table to the other table, retaining their original source and attributes.
3572
If import and export filters are set to accept, then both tables would have
3573
the same content. The transparent mode is the default mode.
3574

    
3575
<p>In the opaque mode, the Pipe protocol retransmits optimal route from one
3576
table to the other table in a similar way like other protocols send and receive
3577
routes. Retransmitted route will have the source set to the Pipe protocol, which
3578
may limit access to protocol specific route attributes. This mode is mainly for
3579
compatibility, it is not suggested for new configs. The mode can be changed by
3580
<tt/mode/ option.
3581

    
3582
<p>The primary use of multiple routing tables and the Pipe protocol is for
3583
policy routing, where handling of a single packet doesn't depend only on its
3584
destination address, but also on its source address, source interface, protocol
3585
type and other similar parameters. In many systems (Linux being a good example),
3586
the kernel allows to enforce routing policies by defining routing rules which
3587
choose one of several routing tables to be used for a packet according to its
3588
parameters. Setting of these rules is outside the scope of BIRD's work (on
3589
Linux, you can use the <tt/ip/ command), but you can create several routing
3590
tables in BIRD, connect them to the kernel ones, use filters to control which
3591
routes appear in which tables and also you can employ the Pipe protocol for
3592
exporting a selected subset of one table to another one.
3593

    
3594
<sect1>Configuration
3595
<label id="pipe-config">
3596

    
3597
<p>Essentially, the Pipe protocol is just a channel connected to a table on both
3598
sides. Therefore, the configuration block for <cf/protocol pipe/ shall directly
3599
include standard channel config options; see the example below.
3600

    
3601
<p><descrip>
3602
	<tag><label id="pipe-peer-table">peer table <m/table/</tag>
3603
	Defines secondary routing table to connect to. The primary one is
3604
	selected by the <cf/table/ keyword.
3605
</descrip>
3606

    
3607
<sect1>Attributes
3608
<label id="pipe-attr">
3609

    
3610
<p>The Pipe protocol doesn't define any route attributes.
3611

    
3612
<sect1>Example
3613
<label id="pipe-exam">
3614

    
3615
<p>Let's consider a router which serves as a boundary router of two different
3616
autonomous systems, each of them connected to a subset of interfaces of the
3617
router, having its own exterior connectivity and wishing to use the other AS as
3618
a backup connectivity in case of outage of its own exterior line.
3619

    
3620
<p>Probably the simplest solution to this situation is to use two routing tables
3621
(we'll call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that
3622
packets having arrived from interfaces belonging to the first AS will be routed
3623
according to <cf/as1/ and similarly for the second AS. Thus we have split our
3624
router to two logical routers, each one acting on its own routing table, having
3625
its own routing protocols on its own interfaces. In order to use the other AS's
3626
routes for backup purposes, we can pass the routes between the tables through a
3627
Pipe protocol while decreasing their preferences and correcting their BGP paths
3628
to reflect the AS boundary crossing.
3629

    
3630
<code>
3631
ipv4 table as1;				# Define the tables
3632
ipv4 table as2;
3633

    
3634
protocol kernel kern1 {			# Synchronize them with the kernel
3635
	ipv4 { table as1; export all; };
3636
	kernel table 1;
3637
}
3638

    
3639
protocol kernel kern2 {
3640
	ipv4 { table as2; export all; };
3641
	kernel table 2;
3642
}
3643

    
3644
protocol bgp bgp1 {			# The outside connections
3645
	ipv4 { table as1; import all; export all; };
3646
	local as 1;
3647
	neighbor 192.168.0.1 as 1001;
3648
}
3649

    
3650
protocol bgp bgp2 {
3651
	ipv4 { table as2; import all; export all; };
3652
	local as 2;
3653
	neighbor 10.0.0.1 as 1002;
3654
}
3655

    
3656
protocol pipe {				# The Pipe
3657
	table as1;
3658
	peer table as2;
3659
	export filter {
3660
		if net ~ [ 1.0.0.0/8+] then {	# Only AS1 networks
3661
			if preference>10 then preference = preference-10;
3662
			if source=RTS_BGP then bgp_path.prepend(1);
3663
			accept;
3664
		}
3665
		reject;
3666
	};
3667
	import filter {
3668
		if net ~ [ 2.0.0.0/8+] then {	# Only AS2 networks
3669
			if preference>10 then preference = preference-10;
3670
			if source=RTS_BGP then bgp_path.prepend(2);
3671
			accept;
3672
		}
3673
		reject;
3674
	};
3675
}
3676
</code>
3677

    
3678

    
3679
<sect>RAdv
3680
<label id="radv">
3681

    
3682
<sect1>Introduction
3683
<label id="radv-intro">
3684

    
3685
<p>The RAdv protocol is an implementation of Router Advertisements, which are
3686
used in the IPv6 stateless autoconfiguration. IPv6 routers send (in irregular
3687
time intervals or as an answer to a request) advertisement packets to connected
3688
networks. These packets contain basic information about a local network (e.g. a
3689
list of network prefixes), which allows network hosts to autoconfigure network
3690
addresses and choose a default route. BIRD implements router behavior as defined
3691
in <rfc id="4861">, router preferences and specific routes (<rfc id="4191">),
3692
and DNS extensions (<rfc id="6106">).
3693

    
3694
<p>The RAdv protocols supports just IPv6 channel.
3695

    
3696
<sect1>Configuration
3697
<label id="radv-config">
3698

    
3699
<p>There are several classes of definitions in RAdv configuration -- interface
3700
definitions, prefix definitions and DNS definitions:
3701

    
3702
<descrip>
3703
	<tag><label id="radv-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
3704
	Interface definitions specify a set of interfaces on which the
3705
	protocol is activated and contain interface specific options.
3706
	See <ref id="proto-iface" name="interface"> common options for
3707
	detailed description.
3708

    
3709
	<tag><label id="radv-prefix">prefix <m/prefix/ { <m/options/ }</tag>
3710
	Prefix definitions allow to modify a list of advertised prefixes. By
3711
	default, the advertised prefixes are the same as the network prefixes
3712
	assigned to the interface. For each network prefix, the matching prefix
3713
	definition is found and its options are used. If no matching prefix
3714
	definition is found, the prefix is used with default options.
3715

    
3716
	Prefix definitions can be either global or interface-specific. The
3717
	second ones are part of interface options. The prefix definition
3718
	matching is done in the first-match style, when interface-specific
3719
	definitions are processed before global definitions. As expected, the
3720
	prefix definition is matching if the network prefix is a subnet of the
3721
	prefix in prefix definition.
3722

    
3723
	<tag><label id="radv-rdnss">rdnss { <m/options/ }</tag>
3724
	RDNSS definitions allow to specify a list of advertised recursive DNS
3725
	servers together with their options. As options are seldom necessary,
3726
	there is also a short variant <cf>rdnss <m/address/</cf> that just
3727
	specifies one DNS server. Multiple definitions are cumulative. RDNSS
3728
	definitions may also be interface-specific when used inside interface
3729
	options. By default, interface uses both global and interface-specific
3730
	options, but that can be changed by <cf/rdnss local/ option.
3731

    
3732
	<tag><label id="radv-dnssl">dnssl { <m/options/ }</tag>
3733
	DNSSL definitions allow to specify a list of advertised DNS search
3734
	domains together with their options. Like <cf/rdnss/ above, multiple
3735
	definitions are cumulative, they can be used also as interface-specific
3736
	options and there is a short variant <cf>dnssl <m/domain/</cf> that just
3737
	specifies one DNS search domain.
3738

    
3739
	<tag><label id="radv-trigger">trigger <m/prefix/</tag>
3740
	RAdv protocol could be configured to change its behavior based on
3741
	availability of routes. When this option is used, the protocol waits in
3742
	suppressed state until a <it/trigger route/ (for the specified network)
3743
	is exported to the protocol, the protocol also returnsd to suppressed
3744
	state if the <it/trigger route/ disappears. Note that route export
3745
	depends on specified export filter, as usual. This option could be used,
3746
	e.g., for handling failover in multihoming scenarios.
3747

    
3748
	During suppressed state, router advertisements are generated, but with
3749
	some fields zeroed. Exact behavior depends on which fields are zeroed,
3750
	this can be configured by <cf/sensitive/ option for appropriate
3751
	fields. By default, just <cf/default lifetime/ (also called <cf/router
3752
	lifetime/) is zeroed, which means hosts cannot use the router as a
3753
	default router. <cf/preferred lifetime/ and <cf/valid lifetime/ could
3754
	also be configured as <cf/sensitive/ for a prefix, which would cause
3755
	autoconfigured IPs to be deprecated or even removed.
3756

    
3757
	<tag><label id="radv-propagate-routes">propagate routes <m/switch/</tag>
3758
	This option controls propagation of more specific routes, as defined in
3759
	<rfc id="4191">. If enabled, all routes exported to the RAdv protocol,
3760
	with the exception of the trigger prefix, are added to advertisments as
3761
	additional options. The lifetime and preference of advertised routes can
3762
	be set individually by <cf/ra_lifetime/ and <cf/ra_preference/ route
3763
	attributes, or per interface by <cf/route lifetime/ and
3764
	<cf/route preference/ options. Default: disabled.
3765

    
3766
	Note that the RFC discourages from sending more than 17 routes and
3767
	recommends the routes to be configured manually.
3768
</descrip>
3769

    
3770
<p>Interface specific options:
3771

    
3772
<descrip>
3773
	<tag><label id="radv-iface-max-ra-interval">max ra interval <m/expr/</tag>
3774
	Unsolicited router advertisements are sent in irregular time intervals.
3775
	This option specifies the maximum length of these intervals, in seconds.
3776
	Valid values are 4-1800. Default: 600
3777

    
3778
	<tag><label id="radv-iface-min-ra-interval">min ra interval <m/expr/</tag>
3779
	This option specifies the minimum length of that intervals, in seconds.
3780
	Must be at least 3 and at most 3/4 * <cf/max ra interval/. Default:
3781
	about 1/3 * <cf/max ra interval/.
3782

    
3783
	<tag><label id="radv-iface-min-delay">min delay <m/expr/</tag>
3784
	The minimum delay between two consecutive router advertisements, in
3785
	seconds. Default: 3
3786

    
3787
	<tag><label id="radv-iface-managed">managed <m/switch/</tag>
3788
	This option specifies whether hosts should use DHCPv6 for IP address
3789
	configuration. Default: no
3790

    
3791
	<tag><label id="radv-iface-other-config">other config <m/switch/</tag>
3792
	This option specifies whether hosts should use DHCPv6 to receive other
3793
	configuration information. Default: no
3794

    
3795
	<tag><label id="radv-iface-link-mtu">link mtu <m/expr/</tag>
3796
	This option specifies which value of MTU should be used by hosts. 0
3797
	means unspecified. Default: 0
3798

    
3799
	<tag><label id="radv-iface-reachable-time">reachable time <m/expr/</tag>
3800
	This option specifies the time (in milliseconds) how long hosts should
3801
	assume a neighbor is reachable (from the last confirmation). Maximum is
3802
	3600000, 0 means unspecified. Default 0.
3803

    
3804
	<tag><label id="radv-iface-retrans-timer">retrans timer <m/expr/</tag>
3805
	This option specifies the time (in milliseconds) how long hosts should
3806
	wait before retransmitting Neighbor Solicitation messages. 0 means
3807
	unspecified. Default 0.
3808

    
3809
	<tag><label id="radv-iface-current-hop-limit">current hop limit <m/expr/</tag>
3810
	This option specifies which value of Hop Limit should be used by
3811
	hosts. Valid values are 0-255, 0 means unspecified. Default: 64
3812

    
3813
	<tag><label id="radv-iface-default-lifetime">default lifetime <m/expr/ [sensitive <m/switch/]</tag>
3814
	This option specifies the time (in seconds) how long (since the receipt
3815
	of RA) hosts may use the router as a default router. 0 means do not use
3816
	as a default router. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3817
	Default: 3 * <cf/max ra	interval/, <cf/sensitive/ yes.
3818

    
3819
	<tag><label id="radv-iface-default-preference">default preference low|medium|high</tag>
3820
	This option specifies the Default Router Preference value to advertise
3821
	to hosts. Default: medium.
3822

    
3823
	<tag><label id="radv-iface-route-lifetime">route lifetime <m/expr/ [sensitive <m/switch/]</tag>
3824
	This option specifies the default value of advertised lifetime for
3825
	specific routes; i.e., the time (in seconds) for how long (since the
3826
	receipt of RA) hosts should consider these routes valid. A special value
3827
	0xffffffff represents infinity. The lifetime can be overriden on a per
3828
	route basis by the <ref id="rta-ra-lifetime" name="ra_lifetime"> route
3829
	attribute. Default: 3 * <cf/max ra interval/, <cf/sensitive/ no.
3830

    
3831
	For the <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3832
	If <cf/sensitive/ is enabled, even the routes with the <cf/ra_lifetime/
3833
	attribute become sensitive to the trigger.
3834

    
3835
	<tag><label id="radv-iface-route-preference">route preference low|medium|high</tag>
3836
	This option specifies the default value of advertised route preference
3837
	for specific routes. The value can be overriden on a per route basis by
3838
	the <ref id="rta-ra-preference" name="ra_preference"> route attribute.
3839
	Default: medium.
3840

    
3841
	<tag><label id="radv-prefix-linger-time">prefix linger time <m/expr/</tag>
3842
	When a prefix or a route disappears, it is advertised for some time with
3843
	zero lifetime, to inform clients it is no longer valid. This option
3844
	specifies the time (in seconds) for how long prefixes are advertised
3845
	that way. Default: 3 * <cf/max ra interval/.
3846

    
3847
	<tag><label id="radv-route-linger-time">route linger time <m/expr/</tag>
3848
	When a prefix or a route disappears, it is advertised for some time with
3849
	zero lifetime, to inform clients it is no longer valid. This option
3850
	specifies the time (in seconds) for how long routes are advertised
3851
	that way. Default: 3 * <cf/max ra interval/.
3852

    
3853
	<tag><label id="radv-iface-rdnss-local">rdnss local <m/switch/</tag>
3854
	Use only local (interface-specific) RDNSS definitions for this
3855
	interface. Otherwise, both global and local definitions are used. Could
3856
	also be used to disable RDNSS for given interface if no local definitons
3857
	are specified. Default: no.
3858

    
3859
	<tag><label id="radv-iface-dnssl-local">dnssl local <m/switch/</tag>
3860
	Use only local DNSSL definitions for this interface. See <cf/rdnss local/
3861
	option above. Default: no.
3862
</descrip>
3863

    
3864
<p>Prefix specific options
3865

    
3866
<descrip>
3867
	<tag><label id="radv-prefix-skip">skip <m/switch/</tag>
3868
	This option allows to specify that given prefix should not be
3869
	advertised. This is useful for making exceptions from a default policy
3870
	of advertising all prefixes. Note that for withdrawing an already
3871
	advertised prefix it is more useful to advertise it with zero valid
3872
	lifetime. Default: no
3873

    
3874
	<tag><label id="radv-prefix-onlink">onlink <m/switch/</tag>
3875
	This option specifies whether hosts may use the advertised prefix for
3876
	onlink determination. Default: yes
3877

    
3878
	<tag><label id="radv-prefix-autonomous">autonomous <m/switch/</tag>
3879
	This option specifies whether hosts may use the advertised prefix for
3880
	stateless autoconfiguration. Default: yes
3881

    
3882
	<tag><label id="radv-prefix-valid-lifetime">valid lifetime <m/expr/ [sensitive <m/switch/]</tag>
3883
	This option specifies the time (in seconds) how long (after the
3884
	receipt of RA) the prefix information is valid, i.e., autoconfigured
3885
	IP addresses can be assigned and hosts with that IP addresses are
3886
	considered directly reachable. 0 means the prefix is no longer
3887
	valid. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3888
	Default: 86400 (1 day), <cf/sensitive/ no.
3889

    
3890
	<tag><label id="radv-prefix-preferred-lifetime">preferred lifetime <m/expr/ [sensitive <m/switch/]</tag>
3891
	This option specifies the time (in seconds) how long (after the
3892
	receipt of RA) IP addresses generated from the prefix using stateless
3893
	autoconfiguration remain preferred. For <cf/sensitive/ option,
3894
	see <ref id="radv-trigger" name="trigger">. Default: 14400 (4 hours),
3895
	<cf/sensitive/ no.
3896
</descrip>
3897

    
3898
<p>RDNSS specific options:
3899

    
3900
<descrip>
3901
	<tag><label id="radv-rdnss-ns">ns <m/address/</tag>
3902
	This option specifies one recursive DNS server. Can be used multiple
3903
	times for multiple servers. It is mandatory to have at least one
3904
	<cf/ns/ option in <cf/rdnss/ definition.
3905

    
3906
	<tag><label id="radv-rdnss-lifetime">lifetime [mult] <m/expr/</tag>
3907
	This option specifies the time how long the RDNSS information may be
3908
	used by clients after the receipt of RA. It is expressed either in
3909
	seconds or (when <cf/mult/ is used) in multiples of <cf/max ra
3910
	interval/. Note that RDNSS information is also invalidated when
3911
	<cf/default lifetime/ expires. 0 means these addresses are no longer
3912
	valid DNS servers. Default: 3 * <cf/max ra interval/.
3913
</descrip>
3914

    
3915
<p>DNSSL specific options:
3916

    
3917
<descrip>
3918
	<tag><label id="radv-dnssl-domain">domain <m/address/</tag>
3919
	This option specifies one DNS search domain. Can be used multiple times
3920
	for multiple domains. It is mandatory to have at least one <cf/domain/
3921
	option in <cf/dnssl/ definition.
3922

    
3923
	<tag><label id="radv-dnssl-lifetime">lifetime [mult] <m/expr/</tag>
3924
	This option specifies the time how long the DNSSL information may be
3925
	used by clients after the receipt of RA. Details are the same as for
3926
	RDNSS <cf/lifetime/ option above. Default: 3 * <cf/max ra interval/.
3927
</descrip>
3928

    
3929
<sect1>Attributes
3930
<label id="radv-attr">
3931

    
3932
<p>RAdv defines two route attributes:
3933

    
3934
<descrip>
3935
	<tag><label id="rta-ra-preference">enum ra_preference/</tag>
3936
	The preference of the route. The value can be <it/RA_PREF_LOW/,
3937
	<it/RA_PREF_MEDIUM/ or <it/RA_PREF_HIGH/. If the attribute is not set,
3938
	the <ref id="radv-iface-route-preference" name="route preference">
3939
	option is used.
3940

    
3941
	<tag><label id="rta-ra-lifetime">int ra_lifetime/</tag>
3942
	The advertised lifetime of the route, in seconds. The special value of
3943
	0xffffffff represents infinity. If the attribute is not set, the
3944
	<ref id="radv-iface-route-lifetime" name="route lifetime">
3945
	option is used.
3946
</descrip>
3947

    
3948
<sect1>Example
3949
<label id="radv-exam">
3950

    
3951
<p><code>
3952
ipv6 table radv_routes;			# Manually configured routes go here
3953

    
3954
protocol static {
3955
	ipv6 { table radv_routes; };
3956

    
3957
	route 2001:0DB8:4000::/48 unreachable;
3958
	route 2001:0DB8:4010::/48 unreachable;
3959

    
3960
	route 2001:0DB8:4020::/48 unreachable {
3961
		ra_preference = RA_PREF_HIGH;
3962
		ra_lifetime = 3600;
3963
	};
3964
}
3965

    
3966
protocol radv {
3967
	propagate routes yes;		# Propagate the routes from the radv_routes table
3968
	ipv6 { table radv_routes; export all; };
3969

    
3970
	interface "eth2" {
3971
		max ra interval 5;	# Fast failover with more routers
3972
		managed yes;		# Using DHCPv6 on eth2
3973
		prefix ::/0 {
3974
			autonomous off;	# So do not autoconfigure any IP
3975
		};
3976
	};
3977

    
3978
	interface "eth*";		# No need for any other options
3979

    
3980
	prefix 2001:0DB8:1234::/48 {
3981
		preferred lifetime 0;	# Deprecated address range
3982
	};
3983

    
3984
	prefix 2001:0DB8:2000::/48 {
3985
		autonomous off;		# Do not autoconfigure
3986
	};
3987

    
3988
	rdnss 2001:0DB8:1234::10;	# Short form of RDNSS
3989

    
3990
	rdnss {
3991
		lifetime mult 10;
3992
		ns 2001:0DB8:1234::11;
3993
		ns 2001:0DB8:1234::12;
3994
	};
3995

    
3996
	dnssl {
3997
		lifetime 3600;
3998
		domain "abc.com";
3999
		domain "xyz.com";
4000
	};
4001
}
4002
</code>
4003

    
4004

    
4005
<sect>RIP
4006
<label id="rip">
4007

    
4008
<sect1>Introduction
4009
<label id="rip-intro">
4010

    
4011
<p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol,
4012
where each router broadcasts (to all its neighbors) distances to all networks it
4013
can reach. When a router hears distance to another network, it increments it and
4014
broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some
4015
network goes unreachable, routers keep telling each other that its distance is
4016
the original distance plus 1 (actually, plus interface metric, which is usually
4017
one). After some time, the distance reaches infinity (that's 15 in RIP) and all
4018
routers know that network is unreachable. RIP tries to minimize situations where
4019
counting to infinity is necessary, because it is slow. Due to infinity being 16,
4020
you can't use RIP on networks where maximal distance is higher than 15
4021
hosts.
4022

    
4023
<p>BIRD supports RIPv1 (<rfc id="1058">), RIPv2 (<rfc id="2453">), RIPng (<rfc
4024
id="2080">), and RIP cryptographic authentication (<rfc id="4822">).
4025

    
4026
<p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
4027
convergence, big network load and inability to handle larger networks makes it
4028
pretty much obsolete. It is still usable on very small networks.
4029

    
4030
<sect1>Configuration
4031
<label id="rip-config">
4032

    
4033
<p>RIP configuration consists mainly of common protocol options and interface
4034
definitions, most RIP options are interface specific. RIPng (RIP for IPv6)
4035
protocol instance can be configured by using <cf/rip ng/ instead of just
4036
<cf/rip/ as a protocol type.
4037

    
4038
<p>RIP needs one IPv4 channel. RIPng needs one IPv6 channel. If no channel is
4039
configured, appropriate channel is defined with default parameters.
4040

    
4041
<code>
4042
protocol rip [ng] [&lt;name&gt;] {
4043
	infinity &lt;number&gt;;
4044
	ecmp &lt;switch&gt; [limit &lt;number&gt;];
4045
	interface &lt;interface pattern&gt; {
4046
		metric &lt;number&gt;;
4047
		mode multicast|broadcast;
4048
		passive &lt;switch&gt;;
4049
		address &lt;ip&gt;;
4050
		port &lt;number&gt;;
4051
		version 1|2;
4052
		split horizon &lt;switch&gt;;
4053
		poison reverse &lt;switch&gt;;
4054
		check zero &lt;switch&gt;;
4055
		update time &lt;number&gt;;
4056
		timeout time &lt;number&gt;;
4057
		garbage time &lt;number&gt;;
4058
		ecmp weight &lt;number&gt;;
4059
		ttl security &lt;switch&gt;; | tx only;
4060
		tx class|dscp &lt;number&gt;;
4061
		tx priority &lt;number&gt;;
4062
		rx buffer &lt;number&gt;;
4063
		tx length &lt;number&gt;;
4064
		check link &lt;switch&gt;;
4065
		authentication none|plaintext|cryptographic;
4066
		password "&lt;text&gt;";
4067
		password "&lt;text&gt;" {
4068
			id &lt;num&gt;;
4069
			generate from "&lt;date&gt;";
4070
			generate to "&lt;date&gt;";
4071
			accept from "&lt;date&gt;";
4072
			accept to "&lt;date&gt;";
4073
			from "&lt;date&gt;";
4074
			to "&lt;date&gt;";
4075
			algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
4076
		};
4077
	};
4078
}
4079
</code>
4080

    
4081
<descrip>
4082
	<tag><label id="rip-infinity">infinity <M>number</M></tag>
4083
	Selects the distance of infinity. Bigger values will make
4084
	protocol convergence even slower. The default value is 16.
4085

    
4086
	<tag><label id="rip-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
4087
	This option specifies whether RIP is allowed to generate ECMP
4088
	(equal-cost multipath) routes. Such routes are used when there are
4089
	several directions to the destination, each with the same (computed)
4090
	cost. This option also allows to specify a limit on maximum number of
4091
	nexthops in one route. By default, ECMP is enabled if supported by
4092
	Kernel. Default value of the limit is 16.
4093

    
4094
	<tag><label id="rip-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
4095
	Interface definitions specify a set of interfaces on which the
4096
	protocol is activated and contain interface specific options.
4097
	See <ref id="proto-iface" name="interface"> common options for
4098
	detailed description.
4099
</descrip>
4100

    
4101
<p>Interface specific options:
4102

    
4103
<descrip>
4104
	<tag><label id="rip-iface-metric">metric <m/num/</tag>
4105
	This option specifies the metric of the interface. When a route is
4106
	received from the interface, its metric is increased by this value
4107
	before further processing. Valid values are 1-255, but values higher
4108
	than infinity has no further meaning. Default: 1.
4109

    
4110
	<tag><label id="rip-iface-mode">mode multicast|broadcast</tag>
4111
	This option selects the mode for RIP to use on the interface. The
4112
	default is multicast mode for RIPv2 and broadcast mode for RIPv1.
4113
	RIPng always uses the multicast mode.
4114

    
4115
	<tag><label id="rip-iface-passive">passive <m/switch/</tag>
4116
	Passive interfaces receive routing updates but do not transmit any
4117
	messages. Default: no.
4118

    
4119
	<tag><label id="rip-iface-address">address <m/ip/</tag>
4120
	This option specifies a destination address used for multicast or
4121
	broadcast messages, the default is the official RIP (224.0.0.9) or RIPng
4122
	(ff02::9) multicast address, or an appropriate broadcast address in the
4123
	broadcast mode.
4124

    
4125
	<tag><label id="rip-iface-port">port <m/number/</tag>
4126
	This option selects an UDP port to operate on, the default is the
4127
	official RIP (520) or RIPng (521) port.
4128

    
4129
	<tag><label id="rip-iface-version">version 1|2</tag>
4130
	This option selects the version of RIP used on the interface. For RIPv1,
4131
	automatic subnet aggregation is not implemented, only classful network
4132
	routes and host routes are propagated. Note that BIRD allows RIPv1 to be
4133
	configured with features that are defined for RIPv2 only, like
4134
	authentication or using multicast sockets. The default is RIPv2 for IPv4
4135
	RIP, the option is not supported for RIPng, as no further versions are
4136
	defined.
4137

    
4138
	<tag><label id="rip-iface-version-only">version only <m/switch/</tag>
4139
	Regardless of RIP version configured for the interface, BIRD accepts
4140
	incoming packets of any RIP version. This option restrict accepted
4141
	packets to the configured version. Default: no.
4142

    
4143
	<tag><label id="rip-iface-split-horizon">split horizon <m/switch/</tag>
4144
	Split horizon is a scheme for preventing routing loops. When split
4145
	horizon is active, routes are not regularly propagated back to the
4146
	interface from which they were received. They are either not propagated
4147
	back at all (plain split horizon) or propagated back with an infinity
4148
	metric (split horizon with poisoned reverse). Therefore, other routers
4149
	on the interface will not consider the router as a part of an
4150
	independent path to the destination of the route. Default: yes.
4151

    
4152
	<tag><label id="rip-iface-poison-reverse">poison reverse <m/switch/</tag>
4153
	When split horizon is active, this option specifies whether the poisoned
4154
	reverse variant (propagating routes back with an infinity metric) is
4155
	used. The poisoned reverse has some advantages in faster convergence,
4156
	but uses more network traffic. Default: yes.
4157

    
4158
	<tag><label id="rip-iface-check-zero">check zero <m/switch/</tag>
4159
	Received RIPv1 packets with non-zero values in reserved fields should
4160
	be discarded. This option specifies whether the check is performed or
4161
	such packets are just processed as usual. Default: yes.
4162

    
4163
	<tag><label id="rip-iface-update-time">update time <m/number/</tag>
4164
	Specifies the number of seconds between periodic updates. A lower number
4165
	will mean faster convergence but bigger network load. Default: 30.
4166

    
4167
	<tag><label id="rip-iface-timeout-time">timeout time <m/number/</tag>
4168
	Specifies the time interval (in seconds) between the last received route
4169
	announcement and the route expiration. After that, the network is
4170
	considered unreachable, but still is propagated with infinity distance.
4171
	Default: 180.
4172

    
4173
	<tag><label id="rip-iface-garbage-time">garbage time <m/number/</tag>
4174
	Specifies the time interval (in seconds) between the route expiration
4175
	and the removal of the unreachable network entry. The garbage interval,
4176
	when a route with infinity metric is propagated, is used for both
4177
	internal (after expiration) and external (after withdrawal) routes.
4178
	Default: 120.
4179

    
4180
	<tag><label id="rip-iface-ecmp-weight">ecmp weight <m/number/</tag>
4181
	When ECMP (multipath) routes are allowed, this value specifies a
4182
	relative weight used for nexthops going through the iface. Valid
4183
	values are 1-256. Default value is 1.
4184

    
4185
	<tag><label id="rip-iface-auth">authentication none|plaintext|cryptographic</tag>
4186
	Selects authentication method to be used. <cf/none/ means that packets
4187
	are not authenticated at all, <cf/plaintext/ means that a plaintext
4188
	password is embedded into each packet, and <cf/cryptographic/ means that
4189
	packets are authenticated using some cryptographic hash function
4190
	selected by option <cf/algorithm/ for each key. The default
4191
	cryptographic algorithm for RIP keys is Keyed-MD5. If you set
4192
	authentication to not-none, it is a good idea to add <cf>password</cf>
4193
	section. Default: none.
4194

    
4195
	<tag><label id="rip-iface-pass">password "<m/text/"</tag>
4196
	Specifies a password used for authentication. See <ref id="proto-pass"
4197
	name="password"> common option for detailed description.
4198

    
4199
	<tag><label id="rip-iface-ttl-security">ttl security [<m/switch/ | tx only]</tag>
4200
	TTL security is a feature that protects routing protocols from remote
4201
	spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
4202
	destined to neighbors. Because TTL is decremented when packets are
4203
	forwarded, it is non-trivial to spoof packets with TTL 255 from remote
4204
	locations.
4205

    
4206
	If this option is enabled, the router will send RIP packets with TTL 255
4207
	and drop received packets with TTL less than 255. If this option si set
4208
	to <cf/tx only/, TTL 255 is used for sent packets, but is not checked
4209
	for received packets. Such setting does not offer protection, but offers
4210
	compatibility with neighbors regardless of whether they use ttl
4211
	security.
4212

    
4213
	For RIPng, TTL security is a standard behavior (required by <rfc
4214
	id="2080">) and therefore default value is yes. For IPv4 RIP, default
4215
	value is no.
4216

    
4217
	<tag><label id="rip-iface-tx-class">tx class|dscp|priority <m/number/</tag>
4218
	These options specify the ToS/DiffServ/Traffic class/Priority of the
4219
	outgoing RIP packets. See <ref id="proto-tx-class" name="tx class"> common
4220
	option for detailed description.
4221

    
4222
	<tag><label id="rip-iface-rx-buffer">rx buffer <m/number/</tag>
4223
	This option specifies the size of buffers used for packet processing.
4224
	The buffer size should be bigger than maximal size of received packets.
4225
	The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
4226

    
4227
	<tag><label id="rip-iface-tx-length">tx length <m/number/</tag>
4228
	This option specifies the maximum length of generated RIP packets. To
4229
	avoid IP fragmentation, it should not exceed the interface MTU value.
4230
	The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
4231

    
4232
	<tag><label id="rip-iface-check-link">check link <m/switch/</tag>
4233
	If set, the hardware link state (as reported by OS) is taken into
4234
	consideration. When the link disappears (e.g. an ethernet cable is
4235
	unplugged), neighbors are immediately considered unreachable and all
4236
	routes received from them are withdrawn. It is possible that some
4237
	hardware drivers or platforms do not implement this feature.
4238
	Default: yes.
4239
</descrip>
4240

    
4241
<sect1>Attributes
4242
<label id="rip-attr">
4243

    
4244
<p>RIP defines two route attributes:
4245

    
4246
<descrip>
4247
	<tag>int <cf/rip_metric/</tag>
4248
	RIP metric of the route (ranging from 0 to <cf/infinity/). When routes
4249
	from different RIP instances are available and all of them have the same
4250
	preference, BIRD prefers the route with lowest <cf/rip_metric/. When a
4251
	non-RIP route is exported to RIP, the default metric is 1.
4252

    
4253
	<tag><label id="rta-rip-tag">int rip_tag/</tag>
4254
	RIP route tag: a 16-bit number which can be used to carry additional
4255
	information with the route (for example, an originating AS number in
4256
	case of external routes). When a non-RIP route is exported to RIP, the
4257
	default tag is 0.
4258
</descrip>
4259

    
4260
<sect1>Example
4261
<label id="rip-exam">
4262

    
4263
<p><code>
4264
protocol rip {
4265
	ipv4 {
4266
		import all;
4267
		export all;
4268
	};
4269
	interface "eth*" {
4270
		metric 2;
4271
		port 1520;
4272
		mode multicast;
4273
		update time 12;
4274
		timeout time 60;
4275
		authentication cryptographic;
4276
		password "secret" { algorithm hmac sha256; };
4277
	};
4278
}
4279
</code>
4280

    
4281

    
4282
<sect>RPKI
4283

    
4284
<sect1>Introduction
4285

    
4286
<p>The Resource Public Key Infrastructure (RPKI) is mechanism for origin
4287
validation of BGP routes (RFC 6480). BIRD supports only so-called RPKI-based
4288
origin validation. There is implemented RPKI to Router (RPKI-RTR) protocol (RFC
4289
6810). It uses some of the RPKI data to allow a router to verify that the
4290
autonomous system announcing an IP address prefix is in fact authorized to do
4291
so. This is not crypto checked so can be violated. But it should prevent the
4292
vast majority of accidental hijackings on the Internet today, e.g. the famous
4293
Pakastani accidental announcement of YouTube's address space.
4294

    
4295
<p>The RPKI-RTR protocol receives and maintains a set of ROAs from a cache
4296
server (also called validator). You can validate routes (RFC 6483) using
4297
function <cf/roa_check()/ in filter and set it as import filter at the BGP
4298
protocol. BIRD should re-validate all of affected routes after RPKI update by
4299
RFC 6811, but we don't support it yet! You can use a BIRD's client command
4300
<cf>reload in <m/bgp_protocol_name/</cf> for manual call of revalidation of all
4301
routes.
4302

    
4303
<sect1>Supported transports
4304
<p>
4305
<itemize>
4306
        <item>Unprotected transport over TCP uses a port 323. The cache server
4307
        and BIRD router should be on the same trusted and controlled network
4308
        for security reasons.
4309
        <item>SSHv2 encrypted transport connection uses the normal SSH port
4310
        22.
4311
</itemize>
4312

    
4313
<sect1>Configuration
4314

    
4315
<p>We currently support just one cache server per protocol. However you can
4316
define more RPKI protocols generally.
4317

    
4318
<code>
4319
protocol rpki [&lt;name&gt;] {
4320
        roa4 { table &lt;tab&gt;; };
4321
        roa6 { table &lt;tab&gt;; };
4322
        remote &lt;ip&gt; | "&lt;domain&gt;" [port &lt;num&gt;];
4323
        port &lt;num&gt;;
4324
        refresh [keep] &lt;num&gt;;
4325
        retry [keep] &lt;num&gt;;
4326
        expire [keep] &lt;num&gt;;
4327
        transport tcp;
4328
        transport ssh {
4329
                bird private key "&lt;/path/to/id_rsa&gt;";
4330
                remote public key "&lt;/path/to/known_host&gt;";
4331
                user "&lt;name&gt;";
4332
        };
4333
}
4334
</code>
4335

    
4336
<p>Alse note that you have to specify the ROA channel. If you want to import
4337
only IPv4 prefixes you have to specify only roa4 channel. Similarly with IPv6
4338
prefixes only. If you want to fetch both IPv4 and even IPv6 ROAs you have to
4339
specify both channels.
4340

    
4341
<sect2>RPKI protocol options
4342
<p>
4343
<descrip>
4344
        <tag>remote <m/ip/ | "<m/hostname/" [port <m/num/]</tag> Specifies
4345
        a destination address of the cache server.  Can be specified by an IP
4346
        address or by full domain name string.  Only one cache can be specified
4347
        per protocol. This option is required.
4348

    
4349
        <tag>port <m/num/</tag> Specifies the port number. The default port
4350
        number is 323 for transport without any encryption and 22 for transport
4351
        with SSH encryption.
4352

    
4353
        <tag>refresh [keep] <m/num/</tag> Time period in seconds. Tells how
4354
        long to wait before next attempting to poll the cache using a Serial
4355
        Query or a Reset Query packet. Must be lower than 86400 seconds (one
4356
        day). Too low value can caused a false positive detection of
4357
        network connection problems.  A keyword <cf/keep/ suppresses updating
4358
        this value by a cache server.
4359
        Default: 3600 seconds
4360

    
4361
        <tag>retry [keep] <m/num/</tag> Time period in seconds between a failed
4362
        Serial/Reset Query and a next attempt.  Maximum allowed value is 7200
4363
        seconds (two hours). Too low value can caused a false positive
4364
        detection of network connection problems.  A keyword <cf/keep/
4365
        suppresses updating this value by a cache server.
4366
        Default: 600 seconds
4367

    
4368
        <tag>expire [keep] <m/num/</tag> Time period in seconds. Received
4369
        records are deleted if the client was unable to successfully refresh
4370
        data for this time period.  Must be in range from 600 seconds (ten
4371
        minutes) to 172800 seconds (two days).  A keyword <cf/keep/
4372
        suppresses updating this value by a cache server.
4373
        Default: 7200 seconds
4374

    
4375
        <tag>transport tcp</tag> Unprotected transport over TCP. It's a default
4376
        transport. Should be used only on secure private networks.
4377
        Default: tcp
4378

    
4379
        <tag>transport ssh { <m/SSH transport options.../ }</tag> It enables a
4380
        SSHv2 transport encryption. Cannot be combined with a TCP transport.
4381
        Default: off
4382
</descrip>
4383

    
4384
<sect3>SSH transport options
4385
<p>
4386
<descrip>
4387
	<tag>bird private key "<m>/path/to/id_rsa</m>"</tag>
4388
	A path to the BIRD's private SSH key for authentication.
4389
	It can be a <cf><m>id_rsa</m></cf> file.
4390

    
4391
	<tag>remote public key "<m>/path/to/known_host</m>"</tag>
4392
	A path to the cache's public SSH key for verification identity
4393
	of the cache server. It could be a path to <cf><m>known_host</m></cf> file.
4394

    
4395
	<tag>user "<m/name/"</tag>
4396
	A SSH user name for authentication. This option is a required.
4397
</descrip>
4398

    
4399
<sect1>Examples
4400
<sect2>BGP origin validation
4401
<p>Policy: Don't import <cf/ROA_INVALID/ routes.
4402
<code>
4403
roa4 table r4;
4404
roa6 table r6;
4405

    
4406
protocol rpki {
4407
	debug all;
4408

    
4409
	roa4 { table r4; };
4410
	roa6 { table r6; };
4411

    
4412
	# Please, do not use rpki-validator.realmv6.org in production
4413
	remote "rpki-validator.realmv6.org" port 8282;
4414

    
4415
	retry keep 5;
4416
	refresh keep 30;
4417
	expire 600;
4418
}
4419

    
4420
filter peer_in_v4 {
4421
	if (roa_check(r4, net, bgp_path.last) = ROA_INVALID) then
4422
	{
4423
		print "Ignore invalid ROA ", net, " for ASN ", bgp_path.last;
4424
		reject;
4425
	}
4426
	accept;
4427
}
4428

    
4429
protocol bgp {
4430
	debug all;
4431
	local as 65000;
4432
	neighbor 192.168.2.1 as 65001;
4433
	ipv4 {
4434
		import filter peer_in_v4;
4435
		export none;
4436
	};
4437
}
4438
</code>
4439

    
4440
<sect2>SSHv2 transport encryption
4441
<p>
4442
<code>
4443
roa4 table r4;
4444
roa6 table r6;
4445

    
4446
protocol rpki {
4447
	debug all;
4448

    
4449
	roa4 { table r4; };
4450
	roa6 { table r6; };
4451

    
4452
	remote 127.0.0.1 port 2345;
4453
	transport ssh {
4454
		bird private key "/home/birdgeek/.ssh/id_rsa";
4455
		remote public key "/home/birdgeek/.ssh/known_hosts";
4456
		user "birdgeek";
4457
	};
4458

    
4459
	# Default interval values
4460
}
4461
</code>
4462

    
4463

    
4464
<sect>Static
4465
<label id="static">
4466

    
4467
<p>The Static protocol doesn't communicate with other routers in the network,
4468
but instead it allows you to define routes manually. This is often used for
4469
specifying how to forward packets to parts of the network which don't use
4470
dynamic routing at all and also for defining sink routes (i.e., those telling to
4471
return packets as undeliverable if they are in your IP block, you don't have any
4472
specific destination for them and you don't want to send them out through the
4473
default route to prevent routing loops).
4474

    
4475
<p>There are three classes of definitions in Static protocol configuration --
4476
global options, static route definitions, and per-route options. Usually, the
4477
definition of the protocol contains mainly a list of static routes.
4478
Static routes have no specific attributes.
4479

    
4480
<p>Global options:
4481

    
4482
<descrip>
4483
	<tag><label id="static-check-link">check link <m/switch/</tag>
4484
	If set, hardware link states of network interfaces are taken into
4485
	consideration.  When link disappears (e.g. ethernet cable is unplugged),
4486
	static routes directing to that interface are removed. It is possible
4487
	that some hardware drivers or platforms do not implement this feature.
4488
	Default: off.
4489

    
4490
	<tag><label id="static-igp-table">igp table <m/name/</tag>
4491
	Specifies a table that is used for route table lookups of recursive
4492
	routes. Default: the same table as the protocol is connected to.
4493
</descrip>
4494

    
4495
<p>Route definitions (each may also contain a block of per-route options):
4496

    
4497
<sect1>Regular routes; MPLS switching rules
4498

    
4499
<p>There exist several types of routes; keep in mind that <m/prefix/ syntax is
4500
<ref id="type-prefix" name="dependent on network type">.
4501

    
4502
<descrip>
4503
	<tag>route <m/prefix/ via <m/ip/|<m/"interface"/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]]</tag>
4504
	Next hop routes may bear one or more <ref id="route-next-hop" name="next hops">.
4505
	Every next hop is preceded by <cf/via/ and configured as shown.
4506

    
4507
	<tag>route <m/prefix/ recursive <m/ip/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]]</tag>
4508
	Recursive nexthop resolves the given IP in the configured IGP table and
4509
	uses that route's next hop. The MPLS stacks are concatenated; on top is
4510
	the IGP's nexthop stack and on bottom is this route's stack.
4511

    
4512
	<tag>route <m/prefix/ blackhole|unreachable|prohibit</tag>
4513
	Special routes specifying to silently drop the packet, return it as
4514
	unreachable or return it as administratively prohibited. First two
4515
	targets are also known as <cf/drop/ and <cf/reject/.
4516
</descrip>
4517

    
4518
<p>When the particular destination is not available (the interface is down or
4519
the next hop of the route is not a neighbor at the moment), Static just
4520
uninstalls the route from the table it is connected to and adds it again as soon
4521
as the destination becomes adjacent again.
4522

    
4523
<sect1>Route Origin Authorization
4524

    
4525
<p>The ROA config is just <cf>route <m/prefix/ max <m/int/ as <m/int/</cf> with no nexthop.
4526

    
4527
<sect1>Flowspec
4528
<label id="flowspec-network-type">
4529

    
4530
<p>The flow specification are rules for routers and firewalls for filtering
4531
purpose. It is described by <rfc id="5575">. There are 3 types of arguments:
4532
<m/inet4/ or <m/inet6/ prefixes, bitmasks matching expressions and numbers
4533
matching expressions.
4534

    
4535
Bitmasks matching is written using <m/value/<cf>/</cf><m/mask/ or
4536
<cf/!/<m/value/<cf>/</cf><m/mask/ pairs. It means that <cf/(/<m/data/ <cf/&/
4537
<m/mask/<cf/)/ is or is not equal to <m/value/.
4538

    
4539
Numbers matching is a matching sequence of numbers and ranges separeted by a
4540
commas (<cf/,/) (e.g. <cf/10,20,30/). Ranges can be written using double dots
4541
<cf/../ notation (e.g. <cf/80..90,120..124/). An alternative notation are
4542
sequence of one or more pairs of relational operators and values separated by
4543
logical operators <cf/&&/ or <cf/||/. Allowed relational operators are <cf/=/,
4544
<cf/!=/, <cf/</, <cf/<=/, <cf/>/, <cf/>=/, <cf/true/ and <cf/false/.
4545

    
4546
<sect2>IPv4 Flowspec
4547

    
4548
<p><descrip>
4549
	<tag><label id="flow-dst">dst <m/inet4/</tag>
4550
	Set a matching destination prefix (e.g. <cf>dst 192.168.0.0/16</cf>).
4551
	Only this option is mandatory in IPv4 Flowspec.
4552

    
4553
	<tag><label id="flow-src">src <m/inet4/</tag>
4554
	Set a matching source prefix (e.g. <cf>src 10.0.0.0/8</cf>).
4555

    
4556
	<tag><label id="flow-proto">proto <m/numbers-match/</tag>
4557
	Set a matching IP protocol numbers (e.g.  <cf/proto 6/).
4558

    
4559
	<tag><label id="flow-port">port <m/numbers-match/</tag>
4560
	Set a matching source or destination TCP/UDP port numbers (e.g.
4561
	<cf>port 1..1023,1194,3306</cf>).
4562

    
4563
	<tag><label id="flow-dport">dport <m/numbers-match/</tag>
4564
	Set a mating destination port numbers (e.g. <cf>dport 49151</cf>).
4565

    
4566
	<tag><label id="flow-sport">sport <m/numbers-match/</tag>
4567
	Set a matching source port numbers (e.g. <cf>sport = 0</cf>).
4568

    
4569
	<tag><label id="flow-icmp-type">icmp type <m/numbers-match/</tag>
4570
	Set a matching type field number of an ICMP packet (e.g. <cf>icmp type
4571
	3</cf>)
4572

    
4573
	<tag><label id="flow-icmp-code">icmp code <m/numbers-match/</tag>
4574
	Set a matching code field number of an ICMP packet (e.g. <cf>icmp code
4575
	1</cf>)
4576

    
4577
	<tag><label id="flow-tcp-flags">tcp flags <m/bitmask-match/</tag>
4578
	Set a matching bitmask for TCP header flags (aka control bits) (e.g.
4579
	<cf>tcp flags 0x03/0x0f;</cf>). The maximum length of mask is 12 bits
4580
	(0xfff).
4581

    
4582
	<tag><label id="flow-length">length <m/numbers-match/</tag>
4583
	Set a matching packet length (e.g. <cf>length > 1500;</cf>)
4584

    
4585
	<tag><label id="flow-dscp">dscp <m/numbers-match/</tag>
4586
	Set a matching DiffServ Code Point number (e.g. <cf>length > 1500;</cf>).
4587

    
4588
	<tag><label id="flow-fragment">fragment <m/fragmentation-type/</tag>
4589
	Set a matching type of packet fragmentation. Allowed fragmentation
4590
	types are <cf/dont_fragment/, <cf/is_fragment/, <cf/first_fragment/,
4591
	<cf/last_fragment/ (e.g. <cf>fragment is_fragment &&
4592
	!dont_fragment</cf>).
4593
</descrip>
4594

    
4595
<p><code>
4596
protocol static {
4597
	flow4;
4598

    
4599
	route flow4 {
4600
		dst 10.0.0.0/8;
4601
		port > 24 && < 30 || 40..50,60..70,80 && >= 90;
4602
		tcp flags 0x03/0x0f;
4603
		length > 1024;
4604
		dscp = 63;
4605
		fragment dont_fragment, is_fragment || !first_fragment;
4606
	};
4607
}
4608
</code>
4609

    
4610
<sect2>Differences for IPv6 Flowspec
4611

    
4612
<p>Flowspec IPv6 are same as Flowspec IPv4 with a few exceptions.
4613
<itemize>
4614
	<item>Prefixes <m/inet6/ can be specified not only with prefix length,
4615
	but with prefix <cf/offset/ <m/num/ too (e.g.
4616
	<cf>::1234:5678:9800:0000/101 offset 64</cf>). Offset means to don't
4617
	care of <m/num/ first bits.
4618
	<item>IPv6 Flowspec hasn't mandatory any flowspec component.
4619
	<item>In IPv6 packets, there is a matching the last next header value
4620
	for a matching IP protocol number (e.g. <cf>next header 6</cf>).
4621
	<item>It is not possible to set <cf>dont_fragment</cf> as a type of
4622
	packet fragmentation.
4623
</itemize>
4624

    
4625
<p><descrip>
4626
	<tag><label id="flow6-dst">dst <m/inet6/ [offset <m/num/]</tag>
4627
	Set a matching destination IPv6 prefix (e.g. <cf>dst
4628
	::1c77:3769:27ad:a11a/128 offset 64</cf>).
4629

    
4630
	<tag><label id="flow6-src">src <m/inet6/ [offset <m/num/]</tag>
4631
	Set a matching source IPv6 prefix (e.g. <cf>src fe80::/64</cf>).
4632

    
4633
	<tag><label id="flow6-next-header">next header <m/numbers-match/</tag>
4634
	Set a matching IP protocol numbers (e.g. <cf>next header != 6</cf>).
4635

    
4636
	<tag><label id="flow6-label">label <m/bitmask-match/</tag>
4637
	Set a 20-bit bitmask for matching Flow Label field in IPv6 packets
4638
	(e.g. <cf>label 0x8e5/0x8e5</cf>).
4639
</descrip>
4640

    
4641
<p><code>
4642
protocol static {
4643
	flow6 { table myflow6; };
4644

    
4645
	route flow6 {
4646
		dst fec0:1122:3344:5566:7788:99aa:bbcc:ddee/128;
4647
		src 0000:0000:0000:0001:1234:5678:9800:0000/101 offset 63;
4648
		next header = 23;
4649
		sport > 24 && < 30 || = 40 || 50,60,70..80;
4650
		dport = 50;
4651
		tcp flags 0x03/0x0f, !0/0xff || 0x33/0x33;
4652
		fragment !is_fragment || !first_fragment;
4653
		label 0xaaaa/0xaaaa && 0x33/0x33;
4654
	};
4655
}
4656
</code>
4657

    
4658
<sect1>Per-route options
4659
<p>
4660
<descrip>
4661
	<tag><label id="static-route-bfd">bfd <m/switch/</tag>
4662
	The Static protocol could use BFD protocol for next hop liveness
4663
	detection. If enabled, a BFD session to the route next hop is created
4664
	and the static route is BFD-controlled -- the static route is announced
4665
	only if the next hop liveness is confirmed by BFD. If the BFD session
4666
	fails, the static route is removed. Note that this is a bit different
4667
	compared to other protocols, which may use BFD as an advisory mechanism
4668
	for fast failure detection but ignores it if a BFD session is not even
4669
	established.
4670

    
4671
	This option can be used for static routes with a direct next hop, or
4672
	also for for individual next hops in a static multipath route (see
4673
	above). Note that BFD protocol also has to be configured, see
4674
	<ref id="bfd" name="BFD"> section for details. Default value is no.
4675

    
4676
	<tag><label id="static-route-filter"><m/filter expression/</tag>
4677
	This is a special option that allows filter expressions to be configured
4678
	on per-route basis. Can be used multiple times. These expressions are
4679
	evaluated when the route is originated, similarly to the import filter
4680
	of the static protocol. This is especially useful for configuring route
4681
	attributes, e.g., <cf/ospf_metric1 = 100;/ for a route that will be
4682
	exported to the OSPF protocol.
4683
</descrip>
4684

    
4685
<sect1>Example static config
4686

    
4687
<p><code>
4688
protocol static {
4689
	ipv4 { table testable; };	# Connect to a non-default routing table
4690
	check link;			# Advertise routes only if link is up
4691
	route 0.0.0.0/0 via 198.51.100.130; # Default route
4692
	route 10.0.0.0/8		# Multipath route
4693
		via 198.51.100.10 weight 2
4694
		via 198.51.100.20 bfd	# BFD-controlled next hop
4695
		via 192.0.2.1;
4696
	route 203.0.113.0/24 unreachable; # Sink route
4697
	route 10.2.0.0/24 via "arc0";	# Secondary network
4698
	route 192.168.10.0/24 via 198.51.100.100 {
4699
		ospf_metric1 = 20;	# Set extended attribute
4700
	}
4701
	route 192.168.10.0/24 via 198.51.100.100 {
4702
		ospf_metric2 = 100;	# Set extended attribute
4703
		ospf_tag = 2;		# Set extended attribute
4704
		bfd;			# BFD-controlled route
4705
	}
4706
}
4707
</code>
4708

    
4709

    
4710
<chapt>Conclusions
4711
<label id="conclusion">
4712

    
4713
<sect>Future work
4714
<label id="future-work">
4715

    
4716
<p>Although BIRD supports all the commonly used routing protocols, there are
4717
still some features which would surely deserve to be implemented in future
4718
versions of BIRD:
4719

    
4720
<itemize>
4721
<item>Opaque LSA's
4722
<item>Route aggregation and flap dampening
4723
<item>Multicast routing protocols
4724
<item>Ports to other systems
4725
</itemize>
4726

    
4727

    
4728
<sect>Getting more help
4729
<label id="help">
4730

    
4731
<p>If you use BIRD, you're welcome to join the bird-users mailing list
4732
(<HTMLURL URL="mailto:bird-users@network.cz" name="bird-users@network.cz">)
4733
where you can share your experiences with the other users and consult
4734
your problems with the authors. To subscribe to the list, visit
4735
<HTMLURL URL="http://bird.network.cz/?m_list" name="http://bird.network.cz/?m_list">.
4736
The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
4737

    
4738
<p>BIRD is a relatively young system and it probably contains some bugs. You can
4739
report any problems to the bird-users list and the authors will be glad to solve
4740
them, but before you do so, please make sure you have read the available
4741
documentation and that you are running the latest version (available at
4742
<HTMLURL URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">).
4743
(Of course, a patch which fixes the bug is always welcome as an attachment.)
4744

    
4745
<p>If you want to understand what is going inside, Internet standards are a good
4746
and interesting reading. You can get them from
4747
<HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or a
4748
nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc"
4749
name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
4750

    
4751
<p><it/Good luck!/
4752

    
4753
</book>
4754

    
4755
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4756
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4767
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