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<!doctype birddoc system>
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<!--
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	BIRD 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 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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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)
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	<item>the Open Shortest Path First protocol (OSPFv2, OSPFv3)
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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 supports either IPv4 or IPv6 protocol, but have to be compiled separately
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for each one. Therefore, a dualstack router would run two instances of BIRD (one
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for IPv4 and one for IPv6), with completely separate setups (configuration
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files, tools ...).
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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/--enable-ipv6/ which enables building
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of an IPv6 version of BIRD, <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>About routing tables
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<label id="routing-tables">
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<p>BIRD has one or more routing tables which may or may not be synchronized with
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OS kernel and which may or may not be synchronized with each other (see the Pipe
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protocol). Each routing table contains a list of known routes. Each route
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consists of:
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<itemize>
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	<item>network prefix this route is for (network address and prefix
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		length -- the number of bits forming the network part of the
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		address; also known as a netmask)
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	<item>preference of this route
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	<item>IP address of router which told us about this route
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	<item>IP address of router we should forward the packets to using this
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		route
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	<item>other attributes common to all routes
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	<item>dynamic attributes defined by protocols which may or may not be
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		present (typically protocol metrics)
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</itemize>
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Routing table maintains multiple entries for a network, but at most one entry
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for one network and one protocol. The entry with the highest preference is used
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for routing (we will call such an entry the <it/selected route/). If there are
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more entries with the same preference and they are from the same protocol, the
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protocol decides (typically according to metrics). If they aren't, an internal
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ordering is used to break the tie. You can get the list of route attributes in
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the Route attributes section.
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<p>Each protocol is connected to a routing table through two filters which can
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accept, reject and modify the routes. An <it/export/ filter checks routes passed
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from the routing table to the protocol, an <it/import/ filter checks routes in
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the opposite direction. When the routing table gets a route from a protocol, it
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recalculates the selected route and broadcasts it to all protocols connected to
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the table. The protocols typically send the update to other routers in the
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network. Note that although most protocols are interested in receiving just
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selected routes, some protocols (e.g. the <cf/Pipe/ protocol) receive and
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process all entries in routing tables (accepted by filters).
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<p><label id="dsc-table-sorted">Usually, a routing table just chooses a selected route
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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>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.). You
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can either use a simple string starting with a letter followed by any
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combination of letters and numbers (e.g. "R123", "myfilter", "bgp5") or you can
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enclose the name into apostrophes (<cf/'/) and than you can use any combination
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of numbers, letters. hyphens, dots and colons (e.g. "'1:strange-name'",
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"'-NAME-'", "'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, scans for new network interfaces every 10 seconds
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and runs RIP on all network interfaces found.
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<code>
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protocol kernel {
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	persist;		# Don't remove routes on BIRD shutdown
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	scan time 20;		# Scan kernel routing table every 20 seconds
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	export all;		# Default is export none
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}
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protocol device {
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	scan time 10;		# Scan interfaces every 10 seconds
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}
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protocol rip {
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	export all;
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	import all;
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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. <m/Filename/ could also
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	be a wildcard, in that case matching files are included in alphabetic
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	order. The maximal depth is 8. Note that this statement could be used
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	anywhere in the config file, not just as a top-level option.
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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>
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	Define a function. You can learn more about functions in the following chapter.
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	<tag><label id="opt-protocol">protocol rip|ospf|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
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	Define a protocol instance called <cf><m/name/</cf> (or with a name like
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	"rip5" generated automatically if you don't specify any
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	<cf><m/name/</cf>). You can learn more about configuring protocols in
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	their own chapters. When <cf>from <m/name2/</cf> expression is used,
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	initial protocol options are taken from protocol or template
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	<cf><m/name2/</cf> You can run more than one instance of most protocols
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	(like RIP or BGP). By default, no instances are configured.
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	<tag><label id="opt-template">template rip|bgp|<m/.../ [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
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	Define a protocol template instance called <m/name/ (or with a name like
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	"bgp1" generated automatically if you don't specify any	<m/name/).
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	Protocol templates can be used to group common options when many
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	similarly configured protocol instances are to be defined. Protocol
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	instances (and other templates) can use templates by using <cf/from/
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	expression and the name of the template. At the moment templates (and
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	<cf/from/ expression) are not implemented for OSPF protocol.
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	<tag><label id="opt-define">define <m/constant/ = <m/expression/</tag>
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	Define a constant. You can use it later in every place you could use a
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	value of the same type. Besides, there are some predefined numeric
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	constants based on /etc/iproute2/rt_* files. A list of defined constants
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	can be seen (together with other symbols) using 'show symbols' command.
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	<tag><label id="opt-router-id">router id <m/IPv4 address/</tag>
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	Set BIRD's router ID. It's a world-wide unique identification of your
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	router, usually one of router's IPv4 addresses. Default: in IPv4
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	version, the lowest IP address of a non-loopback interface. In IPv6
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	version, this option is mandatory.
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	<tag><label id="opt-router-id-from">router id from [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../]</tag>
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	Set BIRD's router ID based on an IP address of an interface specified by
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	an interface pattern. The option is applicable for IPv4 version only.
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	See <ref id="proto-iface" name="interface"> section for detailed
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	description of interface patterns with extended clauses.
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	<tag><label id="opt-listen-bgp">listen bgp [address <m/address/] [port <m/port/] [dual]</tag>
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	This option allows to specify address and port where BGP protocol should
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	listen. It is global option as listening socket is common to all BGP
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	instances. Default is to listen on all addresses (0.0.0.0) and port 179.
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	In IPv6 mode, option <cf/dual/ can be used to specify that BGP socket
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	should accept both IPv4 and IPv6 connections (but even in that case,
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	BIRD would accept IPv6 routes only). Such behavior was default in older
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	versions of BIRD.
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	<tag><label id="opt-graceful-restart">graceful restart wait <m/number/</tag>
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	During graceful restart recovery, BIRD waits for convergence of routing
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	protocols. This option allows to specify a timeout for the recovery to
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	prevent waiting indefinitely if some protocols cannot converge. Default:
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	240 seconds.
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	<tag><label id="opt-timeformat">timeformat route|protocol|base|log "<m/format1/" [<m/limit/ "<m/format2/"]</tag>
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	This option allows to specify a format of date/time used by BIRD. The
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	first argument specifies for which purpose such format is used.
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	<cf/route/ is a format used in 'show route' command output,
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	<cf/protocol/ is used in 'show protocols' command output, <cf/base/ is
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	used for other commands and <cf/log/ is used in a log file.
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	"<m/format1/" is a format string using <it/strftime(3)/ notation (see
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	<it/man strftime/ for details). <m/limit> and "<m/format2/" allow to
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	specify the second format string for times in past deeper than <m/limit/
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 	seconds. There are few shorthands: <cf/iso long/ is a ISO 8601 date/time
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	format (YYYY-MM-DD hh:mm:ss) that can be also specified using <cf/"%F %T"/.
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	<cf/iso short/ is a variant of ISO 8601 that uses just the time format
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	(hh:mm:ss) for near times (up to 20 hours in the past) and the date
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	format (YYYY-MM-DD) for far times. This is a shorthand for
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	<cf/"%T" 72000 "%F"/.
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	By default, BIRD uses the <cf/iso short/ format for <cf/route/ and
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	<cf/protocol/ times, and the <cf/iso long/ format for <cf/base/ and
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	<cf/log/ times.
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	In pre-1.4.0 versions, BIRD used an short, ad-hoc format for <cf/route/
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	and <cf/protocol/ times, and a <cf/iso long/ similar format (DD-MM-YYYY
474
	hh:mm:ss) for <cf/base/ and <cf/log/. These timeformats could be set by
475
	<cf/old short/ and <cf/old long/ compatibility shorthands.
476

    
477
	<tag><label id="opt-table">table <m/name/ [sorted]</tag>
478
	Create a new routing table. The default routing table is created
479
	implicitly, other routing tables have to be added by this command.
480
	Option <cf/sorted/ can be used to enable sorting of routes, see
481
	<ref id="dsc-table-sorted" name="sorted table"> description for details.
482

    
483
	<tag><label id="opt-roa-table">roa table <m/name/ [ { <m/roa table options .../ } ]</tag>
484
	Create a new ROA (Route Origin Authorization) table. ROA tables can be
485
	used to validate route origination of BGP routes. A ROA table contains
486
	ROA entries, each consist of a network prefix, a max prefix length and
487
	an AS number. A ROA entry specifies prefixes which could be originated
488
	by that AS number. ROA tables could be filled with data from RPKI (<rfc
489
	id="6480">) or from public databases like Whois. ROA tables are
490
	examined by <cf/roa_check()/ operator in filters.
491

    
492
	Currently, there is just one option, <cf>roa <m/prefix/ max <m/num/ as
493
	<m/num/</cf>, which can be used to populate the ROA table with static
494
	ROA entries. The option may be used multiple times. Other entries can be
495
	added dynamically by <cf/add roa/ command.
496

    
497
	<tag><label id="opt-eval">eval <m/expr/</tag>
498
	Evaluates given filter expression. It is used by us for	testing of filters.
499
</descrip>
500

    
501

    
502
<sect>Protocol options
503
<label id="protocol-opts">
504

    
505
<p>For each protocol instance, you can configure a bunch of options. Some of
506
them (those described in this section) are generic, some are specific to the
507
protocol (see sections talking about the protocols).
508

    
509
<p>Several options use a <m/switch/ argument. It can be either <cf/on/,
510
<cf/yes/ or a numeric expression with a non-zero value for the option to be
511
enabled or <cf/off/, <cf/no/ or a numeric expression evaluating to zero to
512
disable it. An empty <m/switch/ is equivalent to <cf/on/ ("silence means
513
agreement").
514

    
515
<descrip>
516
	<tag><label id="proto-preference">preference <m/expr/</tag>
517
	Sets the preference of routes generated by this protocol. Default:
518
	protocol dependent.
519

    
520
	<tag><label id="proto-disabled">disabled <m/switch/</tag>
521
	Disables the protocol. You can change the disable/enable status from the
522
	command line interface without needing to touch the configuration.
523
	Disabled protocols are not activated. Default: protocol is enabled.
524

    
525
	<tag><label id="proto-debug">debug all|off|{ states|routes|filters|interfaces|events|packets [, <m/.../] }</tag>
526
	Set protocol debugging options. If asked, each protocol is capable of
527
	writing trace messages about its work to the log (with category
528
	<cf/trace/). You can either request printing of <cf/all/ trace messages
529
	or only of the types selected: <cf/states/ for protocol state changes
530
	(protocol going up, down, starting, stopping etc.), <cf/routes/ for
531
	routes exchanged with the routing table, <cf/filters/ for details on
532
	route filtering, <cf/interfaces/ for interface change events sent to the
533
	protocol, <cf/events/ for events internal to the protocol and <cf/packets/
534
	for packets sent and received by the protocol. Default: off.
535

    
536
	<tag><label id="proto-mrtdump">mrtdump all|off|{ states|messages [, <m/.../] }</tag>
537
	Set protocol MRTdump flags. MRTdump is a standard binary format for
538
	logging information from routing protocols and daemons. These flags
539
	control what kind of information is logged from the protocol to the
540
	MRTdump file (which must be specified by global <cf/mrtdump/ option, see
541
	the previous section). Although these flags are similar to flags of
542
	<cf/debug/ option, their meaning is different and protocol-specific. For
543
	BGP protocol, <cf/states/ logs BGP state changes and <cf/messages/ logs
544
	received BGP messages. Other protocols does not support MRTdump yet.
545

    
546
	<tag><label id="proto-router-id">router id <m/IPv4 address/</tag>
547
	This option can be used to override global router id for a given
548
	protocol. Default: uses global router id.
549

    
550
	<tag><label id="proto-import">import all | none | filter <m/name/ | filter { <m/filter commands/ } | where <m/filter expression/</tag>
551
	Specify a filter to be used for filtering routes coming from the
552
	protocol to the routing table. <cf/all/ is shorthand for <cf/where true/
553
	and <cf/none/ is shorthand for <cf/where false/. Default: <cf/all/.
554

    
555
	<tag><label id="proto-export">export <m/filter/</tag>
556
	This is similar to the <cf>import</cf> keyword, except that it works in
557
	the direction from the routing table to the protocol. Default: <cf/none/.
558

    
559
	<tag><label id="proto-import-keep-filtered">import keep filtered <m/switch/</tag>
560
	Usually, if an import filter rejects a route, the route is forgotten.
561
	When this option is active, these routes are kept in the routing table,
562
	but they are hidden and not propagated to other protocols. But it is
563
	possible to show them using <cf/show route filtered/. Note that this
564
	option does not work for the pipe protocol. Default: off.
565

    
566
	<tag><label id="proto-import-limit">import limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
567
	Specify an import route limit (a maximum number of routes imported from
568
	the protocol) and optionally the action to be taken when the limit is
569
	hit. Warn action just prints warning log message. Block action discards
570
	new routes coming from the protocol. Restart and disable actions shut
571
	the protocol down like appropriate commands. Disable is the default
572
	action if an action is not explicitly specified. Note that limits are
573
	reset during protocol reconfigure, reload or restart. Default: <cf/off/.
574

    
575
	<tag><label id="proto-receive-limit">receive limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
576
	Specify an receive route limit (a maximum number of routes received from
577
	the protocol and remembered). It works almost identically to <cf>import
578
	limit</cf> option, the only difference is that if <cf/import keep
579
	filtered/ option is active, filtered routes are counted towards the
580
	limit and blocked routes are forgotten, as the main purpose of the
581
	receive limit is to protect routing tables from overflow. Import limit,
582
	on the contrary, counts accepted routes only and routes blocked by the
583
	limit are handled like filtered routes. Default: <cf/off/.
584

    
585
	<tag><label id="proto-export-limit">export limit [ <m/number/ | off ] [action warn | block | restart | disable]</tag>
586
	Specify an export route limit, works similarly to the <cf>import
587
	limit</cf> option, but for the routes exported to the protocol. This
588
	option is experimental, there are some problems in details of its
589
	behavior -- the number of exported routes can temporarily exceed the
590
	limit without triggering it during protocol reload, exported routes
591
	counter ignores route blocking and block action also blocks route
592
	updates of already accepted routes -- and these details will probably
593
	change in the future. Default: <cf/off/.
594

    
595
	<tag><label id="proto-description">description "<m/text/"</tag>
596
	This is an optional description of the protocol. It is displayed as a
597
	part of the output of 'show route all' command.
598

    
599
	<tag><label id="proto-table">table <m/name/</tag>
600
	Connect this protocol to a non-default routing table.
601
</descrip>
602

    
603
<p>There are several options that give sense only with certain protocols:
604

    
605
<descrip>
606
	<tag><label id="proto-iface">interface [-] [ "<m/mask/" ] [ <m/prefix/ ] [, <m/.../] [ { <m/option/; [<m/.../] } ]</tag>
607
	Specifies a set of interfaces on which the protocol is activated with
608
	given interface-specific options. A set of interfaces specified by one
609
	interface option is described using an interface pattern. The interface
610
	pattern consists of a sequence of clauses (separated by commas), each
611
	clause is a mask specified as a shell-like pattern. Interfaces are
612
	matched by their name.
613

    
614
	An interface matches the pattern if it matches any of its clauses. If
615
	the clause begins with <cf/-/, matching interfaces are excluded. Patterns
616
	are processed left-to-right, thus <cf/interface "eth0", -"eth*", "*";/
617
	means eth0 and all non-ethernets.
618

    
619
	Some protocols (namely OSPFv2 and Direct) support extended clauses that
620
	may contain a mask, a prefix, or both of them. An interface matches such
621
	clause if its name matches the mask (if specified) and its address
622
	matches the prefix (if specified). Extended clauses are used when the
623
	protocol handles multiple addresses on an interface independently.
624

    
625
	An interface option can be used more times with different interface-specific
626
	options, in that case for given interface the first matching interface
627
	option is used.
628

    
629
	This option is allowed in Babel, BFD, Direct, OSPF, RAdv and RIP
630
	protocols, but in OSPF protocol it is used in the <cf/area/ subsection.
631

    
632
	Default: none.
633

    
634
	Examples:
635

    
636
	<cf>interface "*" { type broadcast; };</cf> - start the protocol on all
637
	interfaces with <cf>type broadcast</cf> option.
638

    
639
	<cf>interface "eth1", "eth4", "eth5" { type ptp; };</cf> - start the
640
	protocol on enumerated interfaces with <cf>type ptp</cf> option.
641

    
642
	<cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
643
	on all interfaces that have address from 192.168.0.0/16, but not from
644
	192.168.1.0/24.
645

    
646
	<cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol
647
	on all interfaces that have address from 192.168.0.0/16, but not from
648
	192.168.1.0/24.
649

    
650
	<cf>interface "eth*" 192.168.1.0/24;</cf> - start the protocol on all
651
	ethernet interfaces that have address from 192.168.1.0/24.
652

    
653
	<tag><label id="proto-tx-class">tx class|dscp <m/num/</tag>
654
	This option specifies the value of ToS/DS/Class field in IP headers of
655
	the outgoing protocol packets. This may affect how the protocol packets
656
	are processed by the network relative to the other network traffic. With
657
	<cf/class/ keyword, the value (0-255) is used for the whole ToS/Class
658
	octet (but two bits reserved for ECN are ignored). With	<cf/dscp/
659
	keyword, the value (0-63) is used just for the DS field in the octet.
660
	Default value is 0xc0 (DSCP 0x30 - CS6).
661

    
662
	<tag><label id="proto-tx-priority">tx priority <m/num/</tag>
663
	This option specifies the local packet priority. This may affect how the
664
	protocol packets are processed in the local TX queues. This option is
665
	Linux specific. Default value is 7 (highest priority, privileged traffic).
666

    
667
	<tag><label id="proto-pass">password "<m/password/" [ { <m>password options</m> } ]</tag>
668
	Specifies a password that can be used by the protocol as a shared secret
669
	key. Password option can be used more times to specify more passwords.
670
	If more passwords are specified, it is a protocol-dependent decision
671
	which one is really used. Specifying passwords does not mean that
672
	authentication is enabled, authentication can be enabled by separate,
673
	protocol-dependent <cf/authentication/ option.
674

    
675
	This option is allowed in BFD, OSPF and RIP protocols. BGP has also
676
	<cf/password/ option, but it is slightly different and described
677
	separately.
678
	Default: none.
679
</descrip>
680

    
681
<p>Password option can contain section with some (not necessary all) password sub-options:
682

    
683
<descrip>
684
	<tag><label id="proto-pass-id">id <M>num</M></tag>
685
	ID of the password, (1-255). If it is not used, BIRD will choose ID based
686
	on an order of the password item in the interface. For example, second
687
	password item in one interface will have default ID 2. ID is used by
688
	some routing protocols to identify which password was used to
689
	authenticate protocol packets.
690

    
691
	<tag><label id="proto-pass-gen-from">generate from "<m/time/"</tag>
692
	The start time of the usage of the password for packet signing.
693
	The format of <cf><m/time/</cf> is <tt>dd-mm-yyyy HH:MM:SS</tt>.
694

    
695
	<tag><label id="proto-pass-gen-to">generate to "<m/time/"</tag>
696
	The last time of the usage of the password for packet signing.
697

    
698
	<tag><label id="proto-pass-accept-from">accept from "<m/time/"</tag>
699
	The start time of the usage of the password for packet verification.
700

    
701
	<tag><label id="proto-pass-accept-to">accept to "<m/time/"</tag>
702
	The last time of the usage of the password for packet verification.
703

    
704
	<tag><label id="proto-pass-from">from "<m/time/"</tag>
705
	Shorthand for setting both <cf/generate from/ and <cf/accept from/.
706

    
707
	<tag><label id="proto-pass-to">to "<m/time/"</tag>
708
	Shorthand for setting both <cf/generate to/ and <cf/accept to/.
709

    
710
	<tag><label id="proto-pass-algorithm">algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 )</tag>
711
	The message authentication algorithm for the password when cryptographic
712
	authentication is enabled. The default value depends on the protocol.
713
	For RIP and OSPFv2 it is Keyed-MD5 (for compatibility), for OSPFv3
714
	protocol it is HMAC-SHA-256.
715

    
716
</descrip>
717

    
718

    
719
<sect>Flowspec network type
720
<label id="flowspec-network-type">
721

    
722
<p>The flow specification are rules for routers and firewalls for filtering
723
purpose. It is described by <rfc id="5575">. There are 3 types of arguments:
724
<m/inet4/ or <m/inet6/ prefixes, bitmasks matching expressions and numbers
725
matching expressions.
726

    
727
Bitmasks matching is written using <m/value/<cf>/</cf><m/mask/ or
728
<cf/!/<m/value/<cf>/</cf><m/mask/ pairs. It means that <cf/(/<m/data/ <cf/&/
729
<m/mask/<cf/)/ is or is not equal to <m/value/.
730

    
731
Numbers matching is a matching sequence of numbers and ranges separeted by a
732
commas (<cf/,/) (e.g. <cf/10,20,30/). Ranges can be written using double dots
733
<cf/../ notation (e.g. <cf/80..90,120..124/). An alternative notation are
734
sequence of one or more pairs of relational operators and values separated by
735
logical operators <cf/&&/ or <cf/||/. Allowed relational operators are <cf/=/,
736
<cf/!=/, <cf/</, <cf/<=/, <cf/>/, <cf/>=/, <cf/true/ and <cf/false/.
737

    
738
<sect1>IPv4 Flowspec
739

    
740
<p><descrip>
741
	<tag><label id="flow-dst">dst <m/inet4/</tag>
742
	Set a matching destination prefix (e.g. <cf>dst 192.168.0.0/16</cf>).
743
	Only this option is mandatory in IPv4 Flowspec.
744

    
745
	<tag><label id="flow-src">src <m/inet4/</tag>
746
	Set a matching source prefix (e.g. <cf>src 10.0.0.0/8</cf>).
747

    
748
	<tag><label id="flow-proto">proto <m/numbers-match/</tag>
749
	Set a matching IP protocol numbers (e.g.  <cf/proto 6/).
750

    
751
	<tag><label id="flow-port">port <m/numbers-match/</tag>
752
	Set a matching source or destination TCP/UDP port numbers (e.g.
753
	<cf>port 1..1023,1194,3306</cf>).
754

    
755
	<tag><label id="flow-dport">dport <m/numbers-match/</tag>
756
	Set a mating destination port numbers (e.g. <cf>dport 49151</cf>).
757

    
758
	<tag><label id="flow-sport">sport <m/numbers-match/</tag>
759
	Set a matching source port numbers (e.g. <cf>sport = 0</cf>).
760

    
761
	<tag><label id="flow-icmp-type">icmp type <m/numbers-match/</tag>
762
	Set a matching type field number of an ICMP packet (e.g. <cf>icmp type
763
	3</cf>)
764

    
765
	<tag><label id="flow-icmp-code">icmp code <m/numbers-match/</tag>
766
	Set a matching code field number of an ICMP packet (e.g. <cf>icmp code
767
	1</cf>)
768

    
769
	<tag><label id="flow-tcp-flags">tcp flags <m/bitmask-match/</tag>
770
	Set a matching bitmask for TCP header flags (aka control bits) (e.g.
771
	<cf>tcp flags 0x03/0x0f;</cf>).
772

    
773
	<tag><label id="flow-length">length <m/numbers-match/</tag>
774
	Set a matching packet length (e.g. <cf>length > 1500;</cf>)
775

    
776
	<tag><label id="flow-dscp">dscp <m/numbers-match/</tag>
777
	Set a matching DiffServ Code Point number (e.g. <cf>length > 1500;</cf>).
778

    
779
	<tag><label id="flow-fragment">fragment <m/fragmentation-type/</tag>
780
	Set a matching type of packet fragmentation. Allowed fragmentation
781
	types are <cf/dont_fragment/, <cf/is_fragment/, <cf/first_fragment/,
782
	<cf/last_fragment/ (e.g. <cf>fragment is_fragment &&
783
	!dont_fragment</cf>).
784
</descrip>
785

    
786
<p><code>
787
protocol static {
788
	flow4;
789

    
790
	route flow4 {
791
		dst 10.0.0.0/8;
792
		port > 24 && < 30 || 40..50,60..70,80 && >= 90;
793
		tcp flags 0x03/0x0f;
794
		length > 1024;
795
		dscp = 63;
796
		fragment dont_fragment, is_fragment || !first_fragment;
797
	} drop;
798
}
799
</code>
800

    
801
<sect1>Differences for IPv6 Flowspec
802

    
803
<p>Flowspec IPv6 are same as Flowspec IPv4 with a few exceptions.
804
<itemize>
805
	<item>Prefixes <m/inet6/ can be specified not only with prefix length,
806
	but with prefix <cf/offset/ <m/num/ too (e.g.
807
	<cf>::1234:5678:9800:0000/101 offset 64</cf>). Offset means to don't
808
	care of <m/num/ first bits.
809
	<item>IPv6 Flowspec hasn't mandatory any flowspec component.
810
	<item>In IPv6 packets, there is a matching the last next header value
811
	for a matching IP protocol number (e.g. <cf>next header 6</cf>).
812
	<item>It is not possible to set <cf>dont_fragment</cf> as a type of
813
	packet fragmentation.
814
</itemize>
815

    
816
<p><descrip>
817
	<tag><label id="flow6-dst">dst <m/inet6/ [offset <m/num/]</tag>
818
	Set a matching destination IPv6 prefix (e.g. <cf>dst
819
	::1c77:3769:27ad:a11a/128 offset 64</cf>).
820

    
821
	<tag><label id="flow6-src">src <m/inet6/ [offset <m/num/]</tag>
822
	Set a matching source IPv6 prefix (e.g. <cf>src fe80::/64</cf>).
823

    
824
	<tag><label id="flow6-next-header">next header <m/numbers-match/</tag>
825
	Set a matching IP protocol numbers (e.g. <cf>next header != 6</cf>).
826

    
827
	<tag><label id="flow6-label">label <m/bitmask-match/</tag>
828
	Set a 20-bit bitmask for matching Flow Label field in IPv6 packets
829
	(e.g. <cf>label 0x8e5/0x8e5</cf>).
830
</descrip>
831

    
832
<p><code>
833
protocol static {
834
	flow6;
835

    
836
	route flow6 {
837
		dst fec0:1122:3344:5566:7788:99aa:bbcc:ddee/128;
838
		src 0000:0000:0000:0001:1234:5678:9800:0000/101 offset 63;
839
		next header = 23;
840
		sport > 24 && < 30 || = 40 || 50,60,70..80;
841
		dport = 50;
842
		tcp flags 0x03/0x0f, !0/0xff || 0x33/0x33;
843
		fragment !is_fragment || !first_fragment;
844
		label 0xaaaa/0xaaaa && 0x33/0x33;
845
	} drop;
846
}
847
</code>
848

    
849
<chapt>Remote control
850
<label id="remote-control">
851

    
852
<p>You can use the command-line client <file>birdc</file> to talk with a running
853
BIRD. Communication is done using a <file/bird.ctl/ UNIX domain socket (unless
854
changed with the <tt/-s/ option given to both the server and the client). The
855
commands can perform simple actions such as enabling/disabling of protocols,
856
telling BIRD to show various information, telling it to show routing table
857
filtered by filter, or asking BIRD to reconfigure. Press <tt/?/ at any time to
858
get online help. Option <tt/-r/ can be used to enable a restricted mode of BIRD
859
client, which allows just read-only commands (<cf/show .../). Option <tt/-v/ can
860
be passed to the client, to make it dump numeric return codes along with the
861
messages. You do not necessarily need to use <file/birdc/ to talk to BIRD, your
862
own applications could do that, too -- the format of communication between BIRD
863
and <file/birdc/ is stable (see the programmer's documentation).
864

    
865
<p>There is also lightweight variant of BIRD client called <file/birdcl/, which
866
does not support command line editing and history and has minimal dependencies.
867
This is useful for running BIRD in resource constrained environments, where
868
Readline library (required for regular BIRD client) is not available.
869

    
870
<p>Many commands have the <m/name/ of the protocol instance as an argument.
871
This argument can be omitted if there exists only a single instance.
872

    
873
<p>Here is a brief list of supported functions:
874

    
875
<descrip>
876
	<tag><label id="cli-show-status">show status</tag>
877
	Show router status, that is BIRD version, uptime and time from last
878
	reconfiguration.
879

    
880
	<tag><label id="cli-show-interfaces">show interfaces [summary]</tag>
881
	Show the list of interfaces. For each interface, print its type, state,
882
	MTU and addresses assigned.
883

    
884
	<tag><label id="cli-show-protocols">show protocols [all]</tag>
885
	Show list of protocol instances along with tables they are connected to
886
	and protocol status, possibly giving verbose information, if <cf/all/ is
887
	specified.
888

    
889
	<tag><label id="cli-show-ospf-iface">show ospf interface [<m/name/] ["<m/interface/"]</tag>
890
	Show detailed information about OSPF interfaces.
891

    
892
	<tag><label id="cli-show-ospf-neighbors">show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
893
	Show a list of OSPF neighbors and a state of adjacency to them.
894

    
895
	<tag><label id="cli-show-ospf-state">show ospf state [all] [<m/name/]</tag>
896
	Show detailed information about OSPF areas based on a content of the
897
	link-state database. It shows network topology, stub networks,
898
	aggregated networks and routers from other areas and external routes.
899
	The command shows information about reachable network nodes, use option
900
	<cf/all/ to show information about all network nodes in the link-state
901
	database.
902

    
903
	<tag><label id="cli-show-ospf-topology">show ospf topology [all] [<m/name/]</tag>
904
	Show a topology of OSPF areas based on a content of the link-state
905
	database. It is just a stripped-down version of 'show ospf state'.
906

    
907
	<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>
908
	Show contents of an OSPF LSA database. Options could be used to filter
909
	entries.
910

    
911
	<tag><label id="cli-show-rip-interfaces">show rip interfaces [<m/name/] ["<m/interface/"]</tag>
912
	Show detailed information about RIP interfaces.
913

    
914
	<tag><label id="cli-show-rip-neighbors">show rip neighbors [<m/name/] ["<m/interface/"]</tag>
915
	Show a list of RIP neighbors and associated state.
916

    
917
	<tag><label id="cli-show-static">show static [<m/name/]</tag>
918
	Show detailed information about static routes.
919

    
920
	<tag><label id="cli-show-bfd-sessions">show bfd sessions [<m/name/]</tag>
921
	Show information about BFD sessions.
922

    
923
	<tag><label id="cli-show-symbols">show symbols [table|filter|function|protocol|template|roa|<m/symbol/]</tag>
924
	Show the list of symbols defined in the configuration (names of
925
	protocols, routing tables etc.).
926

    
927
	<tag><label id="cli-show-route">show route [[for] <m/prefix/|<m/IP/] [table <m/t/] [filter <m/f/|where <m/c/] [(export|preexport|noexport) <m/p/] [protocol <m/p/] [<m/options/]</tag>
928
	Show contents of a routing table (by default of the main one or the
929
	table attached to a respective protocol), that is routes, their metrics
930
	and (in case the <cf/all/ switch is given) all their attributes.
931

    
932
	<p>You can specify a <m/prefix/ if you want to print routes for a
933
	specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
934
	the entry which will be used for forwarding of packets to the given
935
	destination. By default, all routes for each network are printed with
936
	the selected one at the top, unless <cf/primary/ is given in which case
937
	only the selected route is shown.
938

    
939
	<p>You can also ask for printing only routes processed and accepted by
940
	a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
941
	</cf> or matching a given condition (<cf>where <m/condition/</cf>).
942

    
943
	The <cf/export/, <cf/preexport/ and <cf/noexport/ switches ask for
944
	printing of routes that are exported to the specified protocol.
945
	With <cf/preexport/, the export filter of the protocol is skipped.
946
	With <cf/noexport/, routes rejected by the export filter are printed
947
	instead. Note that routes not exported to the protocol for other reasons
948
	(e.g. secondary routes or routes imported from that protocol) are not
949
	printed even with <cf/noexport/.
950

    
951
	<p>You can also select just routes added by a specific protocol.
952
	<cf>protocol <m/p/</cf>.
953

    
954
	<p>If BIRD is configured to keep filtered routes (see <cf/import keep
955
	filtered/ option), you can show them instead of routes by using
956
	<cf/filtered/ switch.
957

    
958
	<p>The <cf/stats/ switch requests showing of route statistics (the
959
	number of networks, number of routes before and after filtering). If
960
	you use <cf/count/ instead, only the statistics will be printed.
961

    
962
	<tag><label id="cli-show-roa">show roa [<m/prefix/ | in <m/prefix/ | for <m/prefix/] [as <m/num/] [table <m/t/]</tag>
963
	Show contents of a ROA table (by default of the first one). You can
964
	specify a <m/prefix/ to print ROA entries for a specific network. If you
965
	use <cf>for <m/prefix/</cf>, you'll get all entries relevant for route
966
	validation of the network prefix; i.e., ROA entries whose prefixes cover
967
	the network prefix. Or you can use <cf>in <m/prefix/</cf> to get ROA
968
	entries covered by the network prefix. You could also use <cf/as/ option
969
	to show just entries for given AS.
970

    
971
	<tag><label id="cli-add-roa">add roa <m/prefix/ max <m/num/ as <m/num/ [table <m/t/]</tag>
972
	Add a new ROA entry to a ROA table. Such entry is called <it/dynamic/
973
	compared to <it/static/ entries specified in the config file. These
974
	dynamic entries survive reconfiguration.
975

    
976
	<tag><label id="cli-delete-roa">delete roa <m/prefix/ max <m/num/ as <m/num/ [table <m/t/]</tag>
977
	Delete the specified ROA entry from a ROA table. Only dynamic ROA
978
	entries (i.e., the ones added by <cf/add roa/ command) can be deleted.
979

    
980
	<tag><label id="cli-flush-roa">flush roa [table <m/t/]</tag>
981
	Remove all dynamic ROA entries from a ROA table.
982

    
983
	<tag><label id="cli-configure">configure [soft] ["<m/config file/"] [timeout [<m/num/]]</tag>
984
	Reload configuration from a given file. BIRD will smoothly switch itself
985
	to the new configuration, protocols are reconfigured if possible,
986
	restarted otherwise. Changes in filters usually lead to restart of
987
	affected protocols.
988

    
989
	If <cf/soft/ option is used, changes in filters does not cause BIRD to
990
	restart affected protocols, therefore already accepted routes (according
991
	to old filters) would be still propagated, but new routes would be
992
	processed according to the new filters.
993

    
994
	If <cf/timeout/ option is used, config timer is activated. The new
995
	configuration could be either confirmed using <cf/configure confirm/
996
	command, or it will be reverted to the old one when the config timer
997
	expires. This is useful for cases when reconfiguration breaks current
998
	routing and a router becomes inaccessible for an administrator. The
999
	config timeout expiration is equivalent to <cf/configure undo/
1000
	command. The timeout duration could be specified, default is 300 s.
1001

    
1002
	<tag><label id="cli-configure-confirm">configure confirm</tag>
1003
	Deactivate the config undo timer and therefore confirm the current
1004
	configuration.
1005

    
1006
	<tag><label id="cli-configure-undo">configure undo</tag>
1007
	Undo the last configuration change and smoothly switch back to the
1008
	previous (stored) configuration. If the last configuration change was
1009
	soft, the undo change is also soft. There is only one level of undo, but
1010
	in some specific cases when several reconfiguration requests are given
1011
	immediately in a row and the intermediate ones are skipped then the undo
1012
	also skips them back.
1013

    
1014
	<tag><label id="cli-configure-check">configure check ["<m/config file/"]</tag>
1015
	Read and parse given config file, but do not use it. useful for checking
1016
	syntactic and some semantic validity of an config file.
1017

    
1018
	<tag><label id="cli-enable-disable-restart">enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
1019
	Enable, disable or restart a given protocol instance, instances matching
1020
	the <cf><m/pattern/</cf> or <cf/all/ instances.
1021

    
1022
	<tag><label id="cli-reload">reload [in|out] <m/name/|"<m/pattern/"|all</tag>
1023
	Reload a given protocol instance, that means re-import routes from the
1024
	protocol instance and re-export preferred routes to the instance. If
1025
	<cf/in/ or <cf/out/ options are used, the command is restricted to one
1026
	direction (re-import or re-export).
1027

    
1028
	This command is useful if appropriate filters have changed but the
1029
	protocol instance was not restarted (or reloaded), therefore it still
1030
	propagates the old set of routes. For example when <cf/configure soft/
1031
	command was used to change filters.
1032

    
1033
	Re-export always succeeds, but re-import is protocol-dependent and might
1034
	fail (for example, if BGP neighbor does not support route-refresh
1035
	extension). In that case, re-export is also skipped. Note that for the
1036
	pipe protocol, both directions are always reloaded together (<cf/in/ or
1037
	<cf/out/ options are ignored in that case).
1038

    
1039
	<tag><label id="cli-down">down</tag>
1040
	Shut BIRD down.
1041

    
1042
	<tag><label id="cli-debug">debug <m/protocol/|<m/pattern/|all all|off|{ states|routes|filters|events|packets [, <m/.../] }</tag>
1043
	Control protocol debugging.
1044

    
1045
	<tag><label id="cli-dump">dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
1046
	Dump contents of internal data structures to the debugging output.
1047

    
1048
	<tag><label id="cli-echo">echo all|off|{ <m/list of log classes/ } [ <m/buffer-size/ ]</tag>
1049
	Control echoing of log messages to the command-line output.
1050
	See <ref id="opt-log" name="log option"> for a list of log classes.
1051

    
1052
	<tag><label id="cli-eval">eval <m/expr/</tag>
1053
	Evaluate given expression.
1054
</descrip>
1055

    
1056

    
1057
<chapt>Filters
1058
<label id="filters">
1059

    
1060
<sect>Introduction
1061
<label id="filters-intro">
1062

    
1063
<p>BIRD contains a simple programming language. (No, it can't yet read mail :-).
1064
There are two objects in this language: filters and functions. Filters are
1065
interpreted by BIRD core when a route is being passed between protocols and
1066
routing tables. The filter language contains control structures such as if's and
1067
switches, but it allows no loops. An example of a filter using many features can
1068
be found in <file>filter/test.conf</file>.
1069

    
1070
<p>Filter gets the route, looks at its attributes and modifies some of them if
1071
it wishes. At the end, it decides whether to pass the changed route through
1072
(using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks like
1073
this:
1074

    
1075
<code>
1076
filter not_too_far
1077
int var;
1078
{
1079
	if defined( rip_metric ) then
1080
		var = rip_metric;
1081
	else {
1082
		var = 1;
1083
		rip_metric = 1;
1084
	}
1085
	if rip_metric &gt; 10 then
1086
		reject "RIP metric is too big";
1087
	else
1088
		accept "ok";
1089
}
1090
</code>
1091

    
1092
<p>As you can see, a filter has a header, a list of local variables, and a body.
1093
The header consists of the <cf/filter/ keyword followed by a (unique) name of
1094
filter. The list of local variables consists of <cf><M>type name</M>;</cf>
1095
pairs where each pair defines one local variable. The body consists of <cf>
1096
{ <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You
1097
can group several statements to a single compound statement by using braces
1098
(<cf>{ <M>statements</M> }</cf>) which is useful if you want to make a bigger
1099
block of code conditional.
1100

    
1101
<p>BIRD supports functions, so that you don't have to repeat the same blocks of
1102
code over and over. Functions can have zero or more parameters and they can have
1103
local variables. Recursion is not allowed. Function definitions look like this:
1104

    
1105
<code>
1106
function name ()
1107
int local_variable;
1108
{
1109
	local_variable = 5;
1110
}
1111

    
1112
function with_parameters (int parameter)
1113
{
1114
	print parameter;
1115
}
1116
</code>
1117

    
1118
<p>Unlike in C, variables are declared after the <cf/function/ line, but before
1119
the first <cf/{/. You can't declare variables in nested blocks. Functions are
1120
called like in C: <cf>name(); with_parameters(5);</cf>. Function may return
1121
values using the <cf>return <m/[expr]/</cf> command. Returning a value exits
1122
from current function (this is similar to C).
1123

    
1124
<p>Filters are declared in a way similar to functions except they can't have
1125
explicit parameters. They get a route table entry as an implicit parameter, it
1126
is also passed automatically to any functions called. The filter must terminate
1127
with either <cf/accept/ or <cf/reject/ statement. If there's a runtime error in
1128
filter, the route is rejected.
1129

    
1130
<p>A nice trick to debug filters is to use <cf>show route filter <m/name/</cf>
1131
from the command line client. An example session might look like:
1132

    
1133
<code>
1134
pavel@bug:~/bird$ ./birdc -s bird.ctl
1135
BIRD 0.0.0 ready.
1136
bird> show route
1137
10.0.0.0/8         dev eth0 [direct1 23:21] (240)
1138
195.113.30.2/32    dev tunl1 [direct1 23:21] (240)
1139
127.0.0.0/8        dev lo [direct1 23:21] (240)
1140
bird> show route ?
1141
show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
1142
bird> show route filter { if 127.0.0.5 &tilde; net then accept; }
1143
127.0.0.0/8        dev lo [direct1 23:21] (240)
1144
bird>
1145
</code>
1146

    
1147

    
1148
<sect>Data types
1149
<label id="data-types">
1150

    
1151
<p>Each variable and each value has certain type. Booleans, integers and enums
1152
are incompatible with each other (that is to prevent you from shooting in the
1153
foot).
1154

    
1155
<descrip>
1156
	<tag><label id="type-bool">bool</tag>
1157
	This is a boolean type, it can have only two values, <cf/true/ and
1158
	<cf/false/. Boolean is the only type you can use in <cf/if/ statements.
1159

    
1160
	<tag><label id="type-int">int</tag>
1161
	This is a general integer type. It is an unsigned 32bit type; i.e., you
1162
	can expect it to store values from 0 to 4294967295. Overflows are not
1163
	checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
1164

    
1165
	<tag><label id="type-pair">pair</tag>
1166
	This is a pair of two short integers. Each component can have values
1167
	from 0 to 65535. Literals of this type are written as <cf/(1234,5678)/.
1168
	The same syntax can also be used to construct a pair from two arbitrary
1169
	integer expressions (for example <cf/(1+2,a)/).
1170

    
1171
	<tag><label id="type-quad">quad</tag>
1172
	This is a dotted quad of numbers used to represent router IDs (and
1173
	others). Each component can have a value from 0 to 255. Literals of
1174
	this type are written like IPv4 addresses.
1175

    
1176
	<tag><label id="type-string">string</tag>
1177
	This is a string of characters. There are no ways to modify strings in
1178
	filters. You can pass them between functions, assign them to variables
1179
	of type <cf/string/, print such variables, use standard string
1180
	comparison operations (e.g. <cf/=, !=, &lt;, &gt;, &lt;=, &gt;=/), but
1181
	you can't concatenate two strings. String literals are written as
1182
	<cf/"This is a string constant"/. Additionally matching (<cf/&tilde;,
1183
	!&tilde;/) operators could be used to match a string value against
1184
	a shell pattern (represented also as a string).
1185

    
1186
	<tag><label id="type-ip">ip</tag>
1187
	This type can hold a single IP address. Depending on the compile-time
1188
	configuration of BIRD you are using, it is either an IPv4 or IPv6
1189
	address; this may be checked by <cf>.is_ip4</cf> which returns <cf/bool/.
1190
        IP addresses are written in the standard notation
1191
	(<cf/10.20.30.40/ or <cf/fec0:3:4::1/). You can apply special operator
1192
	<cf>.mask(<M>num</M>)</cf> on values of type ip. It masks out all but
1193
	first <cf><M>num</M></cf> bits from the IP address. So
1194
	<cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
1195

    
1196
	<tag><label id="type-prefix">prefix</tag>
1197
	This type can hold a network prefix consisting of IP address, prefix
1198
	length and several other values. This is the key in route tables.
1199

    
1200
	Prefixes may be of several types, which can be determined by the special
1201
	operator <cf/.type/. The type may be:
1202

    
1203
	<cf/NET_IP4/ and <cf/NET_IP6/ prefixes hold an IP prefix. The literals
1204
	are written as <cf><m/ipaddress//<m/pxlen/</cf>,
1205
	or <cf><m>ipaddress</m>/<m>netmask</m></cf>. There are two special
1206
	operators on IP prefixes: <cf/.ip/ which extracts the IP address from
1207
	the pair, and <cf/.len/, which separates prefix length from the pair.
1208
	So <cf>1.2.0.0/16.len = 16</cf> is true.
1209

    
1210
	<cf/NET_VPN4/ and <cf/NET_VPN6/ prefixes hold an IP prefix with VPN
1211
	Route Distinguisher (<rfc id="4364">). They support the same special
1212
	operators as IP prefixes, and also <cf/.rd/ which extracts the Route
1213
	Distinguisher. Their literals are written
1214
	as <cf><m/vpnrd/ <m/ipprefix/</cf>
1215

    
1216
	<cf/NET_ROA4/ and <cf/NET_ROA6/ prefixes hold an IP prefix range
1217
	together with an ASN. They support the same special operators as IP
1218
	prefixes, and also <cf/.maxlen/ which extracts maximal prefix length,
1219
	and <cf/.asn/ which extracts the ASN.
1220

    
1221
	<cf/NET_FLOW4/ and <cf/NET_FLOW6/ hold an IP prefix together with a
1222
	flowspec rule. Filters currently don't support flowspec parsing.
1223

    
1224
	<tag><label id="type-ec">ec</tag>
1225
	This is a specialized type used to represent BGP extended community
1226
	values. It is essentially a 64bit value, literals of this type are
1227
	usually written as <cf>(<m/kind/, <m/key/, <m/value/)</cf>, where
1228
	<cf/kind/ is a kind of extended community (e.g. <cf/rt/ / <cf/ro/ for a
1229
	route target / route origin communities), the format and possible values
1230
	of <cf/key/ and <cf/value/ are usually integers, but it depends on the
1231
	used kind. Similarly to pairs, ECs can be constructed using expressions
1232
	for <cf/key/ and <cf/value/ parts, (e.g. <cf/(ro, myas, 3*10)/, where
1233
	<cf/myas/ is an integer variable).
1234

    
1235
	<tag><label id="type-lc">lc</tag>
1236
	This is a specialized type used to represent BGP large community
1237
	values. It is essentially a triplet of 32bit values, where the first
1238
	value is reserved for the AS number of the issuer, while meaning of
1239
	remaining parts is defined by the issuer. Literals of this type are
1240
	written as <cf/(123, 456, 789)/, with any integer values. Similarly to
1241
	pairs, LCs can be constructed using expressions for its parts, (e.g.
1242
	<cf/(myas, 10+20, 3*10)/, where <cf/myas/ is an integer variable).
1243

    
1244
	<tag><label id="type-set">int|pair|quad|ip|prefix|ec|lc|enum set</tag>
1245
	Filters recognize four types of sets. Sets are similar to strings: you
1246
	can pass them around but you can't modify them. Literals of type <cf>int
1247
	set</cf> look like <cf> [ 1, 2, 5..7 ]</cf>. As you can see, both simple
1248
	values and ranges are permitted in sets.
1249

    
1250
	For pair sets, expressions like <cf/(123,*)/ can be used to denote
1251
	ranges (in that case <cf/(123,0)..(123,65535)/). You can also use
1252
	<cf/(123,5..100)/ for range <cf/(123,5)..(123,100)/. You can also use
1253
	<cf/*/ and <cf/a..b/ expressions in the first part of a pair, note that
1254
	such expressions are translated to a set of intervals, which may be
1255
	memory intensive. E.g. <cf/(*,4..20)/ is translated to <cf/(0,4..20),
1256
	(1,4..20), (2,4..20), ... (65535, 4..20)/.
1257

    
1258
	EC sets use similar expressions like pair sets, e.g. <cf/(rt, 123,
1259
	10..20)/ or <cf/(ro, 123, *)/. Expressions requiring the translation
1260
	(like <cf/(rt, *, 3)/) are not allowed (as they usually have 4B range
1261
	for ASNs).
1262

    
1263
	Also LC sets use similar expressions like pair sets. You can use ranges
1264
	and wildcards, but if one field uses that, more specific (later) fields
1265
	must be wildcards. E.g., <cf/(10, 20..30, *)/ or <cf/(10, 20, 30..40)/
1266
	is valid, while <cf/(10, *, 20..30)/ or <cf/(10, 20..30, 40)/ is not
1267
	valid.
1268

    
1269
	You can also use expressions for int, pair, EC and LC set values.
1270
	However, it must be possible to evaluate these expressions before daemon
1271
	boots. So you can use only constants inside them. E.g.
1272

    
1273
	<code>
1274
	 define one=1;
1275
	 define myas=64500;
1276
	 int set odds;
1277
	 pair set ps;
1278
	 ec set es;
1279

    
1280
	 odds = [ one, 2+1, 6-one, 2*2*2-1, 9, 11 ];
1281
	 ps = [ (1,one+one), (3,4)..(4,8), (5,*), (6,3..6), (7..9,*) ];
1282
	 es = [ (rt, myas, 3*10), (rt, myas+one, 0..16*16*16-1), (ro, myas+2, *) ];
1283
	</code>
1284

    
1285
	Sets of prefixes are special: their literals does not allow ranges, but
1286
	allows prefix patterns that are written
1287
	as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
1288
	Prefix <cf><m>ip1</m>/<m>len1</m></cf> matches prefix
1289
	pattern <cf><m>ip2</m>/<m>len2</m>{<m>l</m>,<m>h</m>}</cf> if the
1290
	first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are
1291
	identical and <cf>len1 &lt;= ip1 &lt;= len2</cf>. A valid prefix pattern
1292
	has to satisfy <cf>low &lt;= high</cf>, but <cf/pxlen/ is not
1293
	constrained by <cf/low/ or <cf/high/. Obviously, a prefix matches a
1294
	prefix set literal if it matches any prefix pattern in the prefix set
1295
	literal.
1296

    
1297
	There are also two shorthands for prefix patterns: <cf><m/address//<m/len/+</cf>
1298
	is a shorthand for <cf><m/address//<m/len/{<m/len/,<m/maxlen/}</cf>
1299
	(where <cf><m/maxlen/</cf> is 32 for IPv4 and 128 for IPv6), that means
1300
	network prefix <cf><m/address//<m/len/</cf> and all its	subnets.
1301
	<cf><m/address//<m/len/-</cf> is a shorthand for
1302
	<cf><m/address//<m/len/{0,<m/len/}</cf>, that means network prefix
1303
	<cf><m/address//<m/len/</cf> and all its supernets (network prefixes
1304
	that contain it).
1305

    
1306
	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}
1307
	]</cf> matches prefix <cf>1.0.0.0/8</cf>, all subprefixes of
1308
	<cf>2.0.0.0/8</cf>, all superprefixes of <cf>3.0.0.0/8</cf> and prefixes
1309
	<cf/4.X.X.X/ whose prefix length is 16 to 24. <cf>[ 0.0.0.0/0{20,24} ]</cf>
1310
	matches all prefixes (regardless of IP address) whose prefix length is
1311
	20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP
1312
	address <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 &tilde; [ 1.0.0.0/8{15,17} ]</cf>
1313
	is true, but <cf>1.0.0.0/16 &tilde; [ 1.0.0.0/8- ]</cf> is false.
1314

    
1315
	Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
1316
	in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as
1317
	<cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
1318
	<cf>192.168.0.0/16{24,32}</cf>.
1319

    
1320
	<tag><label id="type-enum">enum</tag>
1321
	Enumeration types are fixed sets of possibilities. You can't define your
1322
	own variables of such type, but some route attributes are of enumeration
1323
	type. Enumeration types are incompatible with each other.
1324

    
1325
	<tag><label id="type-bgppath">bgppath</tag>
1326
	BGP path is a list of autonomous system numbers. You can't write
1327
	literals of this type. There are several special operators on bgppaths:
1328

    
1329
	<cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
1330

    
1331
	<cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
1332

    
1333
	<cf><m/P/.last_nonaggregated</cf> returns the last ASN in the non-aggregated part of the path <m/P/.
1334

    
1335
	Both <cf/first/ and <cf/last/ return zero if there is no appropriate
1336
	ASN, for example if the path contains an AS set element as the first (or
1337
	the last) part. If the path ends with an AS set, <cf/last_nonaggregated/
1338
	may be used to get last ASN before any AS set.
1339

    
1340
	<cf><m/P/.len</cf> returns the length of path <m/P/.
1341

    
1342
	<cf>prepend(<m/P/,<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and
1343
	returns the result.
1344

    
1345
	<cf>delete(<m/P/,<m/A/)</cf> deletes all instances of ASN <m/A/ from
1346
	from path <m/P/ and returns the result. <m/A/ may also be an integer
1347
	set, in that case the operator deletes all ASNs from path <m/P/ that are
1348
	also members of set <m/A/.
1349

    
1350
	<cf>filter(<m/P/,<m/A/)</cf> deletes all ASNs from path <m/P/ that are
1351
	not members of integer set <m/A/. I.e., <cf/filter/ do the same as
1352
	<cf/delete/ with inverted set <m/A/.
1353

    
1354
	Statement <cf><m/P/ = prepend(<m/P/, <m/A/);</cf> can be shortened to
1355
	<cf><m/P/.prepend(<m/A/);</cf> if <m/P/ is appropriate route attribute
1356
	(for example <cf/bgp_path/). Similarly for <cf/delete/ and <cf/filter/.
1357

    
1358
	<tag><label id="type-bgpmask">bgpmask</tag>
1359
	BGP masks are patterns used for BGP path matching (using <cf>path
1360
	&tilde; [= 2 3 5 * =]</cf> syntax). The masks resemble wildcard patterns
1361
	as used by UNIX shells. Autonomous system numbers match themselves,
1362
	<cf/*/ matches any (even empty) sequence of arbitrary AS numbers and
1363
	<cf/?/ matches one arbitrary AS number. For example, if <cf>bgp_path</cf>
1364
 	is 4 3 2 1, then: <tt>bgp_path &tilde; [= * 4 3 * =]</tt> is true,
1365
	but <tt>bgp_path &tilde; [= * 4 5 * =]</tt> is false. BGP mask
1366
	expressions can also contain integer expressions enclosed in parenthesis
1367
	and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>. You can
1368
        also use ranges, for example <tt>[= * 3..5 2 100..200 * =]</tt>.
1369
        There is also old (deprecated) syntax that uses / .. / instead of [= .. =]
1370
        and ? instead of *.
1371

    
1372
	<tag><label id="type-clist">clist</tag>
1373
	Clist is similar to a set, except that unlike other sets, it can be
1374
	modified. The type is used for community list (a set of pairs) and for
1375
	cluster list (a set of quads). There exist no literals of this type.
1376
	There are three special operators on clists:
1377

    
1378
	<cf><m/C/.len</cf> returns the length of clist <m/C/.
1379

    
1380
	<cf>add(<m/C/,<m/P/)</cf> adds pair (or quad) <m/P/ to clist <m/C/ and
1381
	returns the result. If item <m/P/ is already in clist <m/C/, it does
1382
	nothing. <m/P/ may also be a clist, in that case all its members are
1383
	added; i.e., it works as clist union.
1384

    
1385
	<cf>delete(<m/C/,<m/P/)</cf> deletes pair (or quad) <m/P/ from clist
1386
	<m/C/ and returns the result. If clist <m/C/ does not contain item
1387
	<m/P/, it does nothing. <m/P/ may also be a pair (or quad) set, in that
1388
	case the operator deletes all items from clist <m/C/ that are also
1389
	members of set <m/P/. Moreover, <m/P/ may also be a clist, which works
1390
	analogously; i.e., it works as clist difference.
1391

    
1392
	<cf>filter(<m/C/,<m/P/)</cf> deletes all items from clist <m/C/ that are
1393
	not members of pair (or quad) set <m/P/. I.e., <cf/filter/ do the same
1394
	as <cf/delete/ with inverted set <m/P/. <m/P/ may also be a clist, which
1395
	works analogously; i.e., it works as clist intersection.
1396

    
1397
	Statement <cf><m/C/ = add(<m/C/, <m/P/);</cf> can be shortened to
1398
	<cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route attribute (for
1399
	example <cf/bgp_community/). Similarly for <cf/delete/ and <cf/filter/.
1400

    
1401
	<tag><label id="type-eclist">eclist</tag>
1402
	Eclist is a data type used for BGP extended community lists. Eclists
1403
	are very similar to clists, but they are sets of ECs instead of pairs.
1404
	The same operations (like <cf/add/, <cf/delete/ or <cf/&tilde;/ and
1405
	<cf/!&tilde;/ membership operators) can be used to modify or test
1406
	eclists, with ECs instead of pairs as arguments.
1407

    
1408
	<tag><label id="type-lclist">lclist/</tag>
1409
	Lclist is a data type used for BGP large community lists. Like eclists,
1410
	lclists are very similar to clists, but they are sets of LCs instead of
1411
	pairs. The same operations (like <cf/add/, <cf/delete/ or <cf/&tilde;/
1412
	and <cf/!&tilde;/ membership operators) can be used to modify or test
1413
	lclists, with LCs instead of pairs as arguments.
1414
</descrip>
1415

    
1416

    
1417
<sect>Operators
1418
<label id="operators">
1419

    
1420
<p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>,
1421
parentheses <cf/(a*(b+c))/, comparison <cf/(a=b, a!=b, a&lt;b, a&gt;=b)/.
1422
Logical operations include unary not (<cf/!/), and (<cf/&amp;&amp;/) and or
1423
(<cf/&verbar;&verbar;/). Special operators include (<cf/&tilde;/,
1424
<cf/!&tilde;/) for "is (not) element of a set" operation - it can be used on
1425
element and set of elements of the same type (returning true if element is
1426
contained in the given set), or on two strings (returning true if first string
1427
matches a shell-like pattern stored in second string) or on IP and prefix
1428
(returning true if IP is within the range defined by that prefix), or on prefix
1429
and prefix (returning true if first prefix is more specific than second one) or
1430
on bgppath and bgpmask (returning true if the path matches the mask) or on
1431
number and bgppath (returning true if the number is in the path) or on bgppath
1432
and int (number) set (returning true if any ASN from the path is in the set) or
1433
on pair/quad and clist (returning true if the pair/quad is element of the
1434
clist) or on clist and pair/quad set (returning true if there is an element of
1435
the clist that is also a member of the pair/quad set).
1436

    
1437
<p>There is one operator related to ROA infrastructure - <cf/roa_check()/. It
1438
examines a ROA table and does <rfc id="6483"> route origin validation for a
1439
given network prefix. The basic usage is <cf>roa_check(<m/table/)</cf>, which
1440
checks current route (which should be from BGP to have AS_PATH argument) in the
1441
specified ROA table and returns ROA_UNKNOWN if there is no relevant ROA,
1442
ROA_VALID if there is a matching ROA, or ROA_INVALID if there are some relevant
1443
ROAs but none of them match. There is also an extended variant
1444
<cf>roa_check(<m/table/, <m/prefix/, <m/asn/)</cf>, which allows to specify a
1445
prefix and an ASN as arguments.
1446

    
1447

    
1448
<sect>Control structures
1449
<label id="control-structures">
1450

    
1451
<p>Filters support two control structures: conditions and case switches.
1452

    
1453
<p>Syntax of a condition is: <cf>if <M>boolean expression</M> then <m/command1/;
1454
else <m/command2/;</cf> and you can use <cf>{ <m/command_1/; <m/command_2/;
1455
<M>...</M> }</cf> instead of either command. The <cf>else</cf> clause may be
1456
omitted. If the <cf><m>boolean expression</m></cf> is true, <m/command1/ is
1457
executed, otherwise <m/command2/ is executed.
1458

    
1459
<p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case
1460
<m/expr/ { else: | <m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [
1461
... ] }</cf>. The expression after <cf>case</cf> can be of any type which can be
1462
on the left side of the &tilde; operator and anything that could be a member of
1463
a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/
1464
grouping. If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements
1465
between it and next <cf/:/ statement are executed. If <cf><m/expr/</cf> matches
1466
neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
1467

    
1468
<p>Here is example that uses <cf/if/ and <cf/case/ structures:
1469

    
1470
<code>
1471
case arg1 {
1472
	2: print "two"; print "I can do more commands without {}";
1473
	3 .. 5: print "three to five";
1474
	else: print "something else";
1475
}
1476

    
1477
if 1234 = i then printn "."; else {
1478
  print "not 1234";
1479
  print "You need {} around multiple commands";
1480
}
1481
</code>
1482

    
1483

    
1484
<sect>Route attributes
1485
<label id="route-attributes">
1486

    
1487
<p>A filter is implicitly passed a route, and it can access its attributes just
1488
like it accesses variables. Attempts to access undefined attribute result in a
1489
runtime error; you can check if an attribute is defined by using the
1490
<cf>defined( <m>attribute</m> )</cf> operator. One notable exception to this
1491
rule are attributes of clist type, where undefined value is regarded as empty
1492
clist for most purposes.
1493

    
1494
<descrip>
1495
	<tag><label id="rta-net"><m/prefix/ net</tag>
1496
	Network the route is talking about. Read-only. (See the chapter about
1497
	routing tables.)
1498

    
1499
	<tag><label id="rta-scope"><m/enum/ scope</tag>
1500
	The scope of the route. Possible values: <cf/SCOPE_HOST/ for routes
1501
	local to this host, <cf/SCOPE_LINK/ for those specific for a physical
1502
	link, <cf/SCOPE_SITE/ and <cf/SCOPE_ORGANIZATION/ for private routes and
1503
	<cf/SCOPE_UNIVERSE/ for globally visible routes. This attribute is not
1504
	interpreted by BIRD and can be used to mark routes in filters. The
1505
	default value for new routes is <cf/SCOPE_UNIVERSE/.
1506

    
1507
	<tag><label id="rta-preference"><m/int/ preference</tag>
1508
	Preference of the route. Valid values are 0-65535. (See the chapter
1509
	about routing tables.)
1510

    
1511
	<tag><label id="rta-from"><m/ip/ from</tag>
1512
	The router which the route has originated from.
1513

    
1514
	<tag><label id="rta-gw"><m/ip/ gw</tag>
1515
	Next hop packets routed using this route should be forwarded to.
1516

    
1517
	<tag><label id="rta-proto"><m/string/ proto</tag>
1518
	The name of the protocol which the route has been imported from.
1519
	Read-only.
1520

    
1521
	<tag><label id="rta-source"><m/enum/ source</tag>
1522
	what protocol has told me about this route. Possible values:
1523
	<cf/RTS_DUMMY/, <cf/RTS_STATIC/, <cf/RTS_INHERIT/, <cf/RTS_DEVICE/,
1524
	<cf/RTS_STATIC_DEVICE/, <cf/RTS_REDIRECT/, <cf/RTS_RIP/, <cf/RTS_OSPF/,
1525
	<cf/RTS_OSPF_IA/, <cf/RTS_OSPF_EXT1/, <cf/RTS_OSPF_EXT2/, <cf/RTS_BGP/,
1526
	<cf/RTS_PIPE/, <cf/RTS_BABEL/.
1527

    
1528
	<tag><label id="rta-cast"><m/enum/ cast</tag>
1529
	Route type (Currently <cf/RTC_UNICAST/ for normal routes,
1530
	<cf/RTC_BROADCAST/, <cf/RTC_MULTICAST/, <cf/RTC_ANYCAST/ will be used in
1531
	the future for broadcast, multicast and anycast routes). Read-only.
1532

    
1533
	<tag><label id="rta-dest"><m/enum/ dest</tag>
1534
	Type of destination the packets should be sent to
1535
	(<cf/RTD_ROUTER/ for forwarding to a neighboring router,
1536
	<cf/RTD_DEVICE/ for routing to a directly-connected network,
1537
	<cf/RTD_MULTIPATH/ for multipath destinations,
1538
	<cf/RTD_BLACKHOLE/ for packets to be silently discarded,
1539
	<cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that should be
1540
	returned with ICMP host unreachable / ICMP administratively prohibited
1541
	messages). Can be changed, but only to <cf/RTD_BLACKHOLE/,
1542
	<cf/RTD_UNREACHABLE/ or <cf/RTD_PROHIBIT/.
1543

    
1544
	<tag><label id="rta-ifname"><m/string/ ifname</tag>
1545
	Name of the outgoing interface. Sink routes (like blackhole, unreachable
1546
	or prohibit) and multipath routes have no interface associated with
1547
	them, so <cf/ifname/ returns an empty string for such routes. Read-only.
1548

    
1549
	<tag><label id="rta-ifindex"><m/int/ ifindex</tag>
1550
	Index of the outgoing interface. System wide index of the interface. May
1551
	be used for interface matching, however indexes might change on interface
1552
	creation/removal. Zero is returned for routes with undefined outgoing
1553
	interfaces. Read-only.
1554

    
1555
	<tag><label id="rta-igp-metric"><m/int/ igp_metric</tag>
1556
	The optional attribute that can be used to specify a distance to the
1557
	network for routes that do not have a native protocol metric attribute
1558
	(like <cf/ospf_metric1/ for OSPF routes). It is used mainly by BGP to
1559
	compare internal distances to boundary routers (see below). It is also
1560
	used when the route is exported to OSPF as a default value for OSPF type
1561
	1 metric.
1562
</descrip>
1563

    
1564
<p>There also exist some protocol-specific attributes which are described in the
1565
corresponding protocol sections.
1566

    
1567

    
1568
<sect>Other statements
1569
<label id="other-statements">
1570

    
1571
<p>The following statements are available:
1572

    
1573
<descrip>
1574
	<tag><label id="assignment"><m/variable/ = <m/expr/</tag>
1575
	Set variable to a given value.
1576

    
1577
	<tag><label id="filter-accept-reject">accept|reject [ <m/expr/ ]</tag>
1578
	Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
1579

    
1580
	<tag><label id="return">return <m/expr/</tag>
1581
	Return <cf><m>expr</m></cf> from the current function, the function ends
1582
	at this point.
1583

    
1584
	<tag><label id="print">print|printn <m/expr/ [<m/, expr.../]</tag>
1585
	Prints given expressions; useful mainly while debugging filters. The
1586
	<cf/printn/ variant does not terminate the line.
1587

    
1588
	<tag><label id="quitbird">quitbird</tag>
1589
	Terminates BIRD. Useful when debugging the filter interpreter.
1590
</descrip>
1591

    
1592

    
1593
<chapt>Protocols
1594
<label id="protocols">
1595

    
1596
<sect>Babel
1597
<label id="babel">
1598

    
1599
<sect1>Introduction
1600
<label id="babel-intro">
1601

    
1602
<p>The Babel protocol
1603
(<rfc id="6126">) is a loop-avoiding distance-vector routing protocol that is
1604
robust and efficient both in ordinary wired networks and in wireless mesh
1605
networks. Babel is conceptually very simple in its operation and "just works"
1606
in its default configuration, though some configuration is possible and in some
1607
cases desirable.
1608

    
1609
<p>While the Babel protocol is dual stack (i.e., can carry both IPv4 and IPv6
1610
routes over the same IPv6 transport), BIRD presently implements only the IPv6
1611
subset of the protocol. No Babel extensions are implemented, but the BIRD
1612
implementation can coexist with implementations using the extensions (and will
1613
just ignore extension messages).
1614

    
1615
<p>The Babel protocol implementation in BIRD is currently in alpha stage.
1616

    
1617
<sect1>Configuration
1618
<label id="babel-config">
1619

    
1620
<p>Babel supports no global configuration options apart from those common to all
1621
other protocols, but supports the following per-interface configuration options:
1622

    
1623
<code>
1624
protocol babel [<name>] {
1625
	interface <interface pattern> {
1626
		type <wired|wireless>;
1627
		rxcost <number>;
1628
		hello interval <number>;
1629
		update interval <number>;
1630
		port <number>;
1631
		tx class|dscp <number>;
1632
		tx priority <number>;
1633
		rx buffer <number>;
1634
		tx length <number>;
1635
		check link <switch>;
1636
	};
1637
}
1638
</code>
1639

    
1640
<descrip>
1641
      <tag><label id="babel-type">type wired|wireless </tag>
1642
      This option specifies the interface type: Wired or wireless. Wired
1643
      interfaces are considered more reliable, and so the default hello
1644
      interval is higher, and a neighbour is considered unreachable after only
1645
      a small number of "hello" packets are lost. On wireless interfaces,
1646
      hello packets are sent more often, and the ETX link quality estimation
1647
      technique is used to compute the metrics of routes discovered over this
1648
      interface. This technique will gradually degrade the metric of routes
1649
      when packets are lost rather than the more binary up/down mechanism of
1650
      wired type links. Default: <cf/wired/.
1651

    
1652
      <tag><label id="babel-rxcost">rxcost <m/num/</tag>
1653
      This specifies the RX cost of the interface. The route metrics will be
1654
      computed from this value with a mechanism determined by the interface
1655
      <cf/type/. Default: 96 for wired interfaces, 256 for wireless.
1656

    
1657
      <tag><label id="babel-hello">hello interval <m/num/</tag>
1658
      Interval at which periodic "hello" messages are sent on this interface,
1659
      in seconds. Default: 4 seconds.
1660

    
1661
      <tag><label id="babel-update">update interval <m/num/</tag>
1662
      Interval at which periodic (full) updates are sent. Default: 4 times the
1663
      hello interval.
1664

    
1665
      <tag><label id="babel-port">port <m/number/</tag>
1666
      This option selects an UDP port to operate on. The default is to operate
1667
      on port 6696 as specified in the Babel RFC.
1668

    
1669
      <tag><label id="babel-tx-class">tx class|dscp|priority <m/number/</tag>
1670
      These options specify the ToS/DiffServ/Traffic class/Priority of the
1671
      outgoing Babel packets. See <ref id="proto-tx-class" name="tx class"> common
1672
      option for detailed description.
1673

    
1674
      <tag><label id="babel-rx-buffer">rx buffer <m/number/</tag>
1675
      This option specifies the size of buffers used for packet processing.
1676
      The buffer size should be bigger than maximal size of received packets.
1677
      The default value is the interface MTU, and the value will be clamped to a
1678
      minimum of 512 bytes + IP packet overhead.
1679

    
1680
      <tag><label id="babel-tx-length">tx length <m/number/</tag>
1681
      This option specifies the maximum length of generated Babel packets. To
1682
      avoid IP fragmentation, it should not exceed the interface MTU value.
1683
      The default value is the interface MTU value, and the value will be
1684
      clamped to a minimum of 512 bytes + IP packet overhead.
1685

    
1686
      <tag><label id="babel-check-link">check link <m/switch/</tag>
1687
      If set, the hardware link state (as reported by OS) is taken into
1688
      consideration. When the link disappears (e.g. an ethernet cable is
1689
      unplugged), neighbors are immediately considered unreachable and all
1690
      routes received from them are withdrawn. It is possible that some
1691
      hardware drivers or platforms do not implement this feature. Default:
1692
      yes.
1693
</descrip>
1694

    
1695
<sect1>Attributes
1696
<label id="babel-attr">
1697

    
1698
<p>Babel defines just one attribute: the internal babel metric of the route. It
1699
is exposed as the <cf/babel_metric/ attribute and has range from 1 to infinity
1700
(65535).
1701

    
1702
<sect1>Example
1703
<label id="babel-exam">
1704

    
1705
<p><code>
1706
protocol babel {
1707
	interface "eth*" {
1708
		type wired;
1709
	};
1710
	interface "wlan0", "wlan1" {
1711
		type wireless;
1712
		hello interval 1;
1713
		rxcost 512;
1714
	};
1715
	interface "tap0";
1716

    
1717
	# This matches the default of babeld: redistribute all addresses
1718
	# configured on local interfaces, plus re-distribute all routes received
1719
	# from other babel peers.
1720

    
1721
	export where (source = RTS_DEVICE) || (source = RTS_BABEL);
1722
}
1723
</code>
1724

    
1725

    
1726
<sect>BFD
1727
<label id="bfd">
1728

    
1729
<sect1>Introduction
1730
<label id="bfd-intro">
1731

    
1732
<p>Bidirectional Forwarding Detection (BFD) is not a routing protocol itself, it
1733
is an independent tool providing liveness and failure detection. Routing
1734
protocols like OSPF and BGP use integrated periodic "hello" messages to monitor
1735
liveness of neighbors, but detection times of these mechanisms are high (e.g. 40
1736
seconds by default in OSPF, could be set down to several seconds). BFD offers
1737
universal, fast and low-overhead mechanism for failure detection, which could be
1738
attached to any routing protocol in an advisory role.
1739

    
1740
<p>BFD consists of mostly independent BFD sessions. Each session monitors an
1741
unicast bidirectional path between two BFD-enabled routers. This is done by
1742
periodically sending control packets in both directions. BFD does not handle
1743
neighbor discovery, BFD sessions are created on demand by request of other
1744
protocols (like OSPF or BGP), which supply appropriate information like IP
1745
addresses and associated interfaces. When a session changes its state, these
1746
protocols are notified and act accordingly (e.g. break an OSPF adjacency when
1747
the BFD session went down).
1748

    
1749
<p>BIRD implements basic BFD behavior as defined in <rfc id="5880"> (some
1750
advanced features like the echo mode or authentication are not implemented), IP
1751
transport for BFD as defined in <rfc id="5881"> and <rfc id="5883"> and
1752
interaction with client protocols as defined in <rfc id="5882">.
1753

    
1754
<p>Note that BFD implementation in BIRD is currently a new feature in
1755
development, expect some rough edges and possible UI and configuration changes
1756
in the future. Also note that we currently support at most one protocol instance.
1757

    
1758
<p>BFD packets are sent with a dynamic source port number. Linux systems use by
1759
default a bit different dynamic port range than the IANA approved one
1760
(49152-65535). If you experience problems with compatibility, please adjust
1761
<cf>/proc/sys/net/ipv4/ip_local_port_range</cf>
1762

    
1763
<sect1>Configuration
1764
<label id="bfd-config">
1765

    
1766
<p>BFD configuration consists mainly of multiple definitions of interfaces.
1767
Most BFD config options are session specific. When a new session is requested
1768
and dynamically created, it is configured from one of these definitions. For
1769
sessions to directly connected neighbors, <cf/interface/ definitions are chosen
1770
based on the interface associated with the session, while <cf/multihop/
1771
definition is used for multihop sessions. If no definition is relevant, the
1772
session is just created with the default configuration. Therefore, an empty BFD
1773
configuration is often sufficient.
1774

    
1775
<p>Note that to use BFD for other protocols like OSPF or BGP, these protocols
1776
also have to be configured to request BFD sessions, usually by <cf/bfd/ option.
1777

    
1778
<p>Some of BFD session options require <m/time/ value, which has to be specified
1779
with the appropriate unit: <m/num/ <cf/s/|<cf/ms/|<cf/us/. Although microseconds
1780
are allowed as units, practical minimum values are usually in order of tens of
1781
milliseconds.
1782

    
1783
<code>
1784
protocol bfd [&lt;name&gt;] {
1785
	interface &lt;interface pattern&gt; {
1786
		interval &lt;time&gt;;
1787
		min rx interval &lt;time&gt;;
1788
		min tx interval &lt;time&gt;;
1789
		idle tx interval &lt;time&gt;;
1790
		multiplier &lt;num&gt;;
1791
		passive &lt;switch&gt;;
1792
		authentication none;
1793
		authentication simple;
1794
		authentication [meticulous] keyed md5|sha1;
1795
		password "&lt;text&gt;";
1796
		password "&lt;text&gt;" {
1797
			id &lt;num&gt;;
1798
			generate from "&lt;date&gt;";
1799
			generate to "&lt;date&gt;";
1800
			accept from "&lt;date&gt;";
1801
			accept to "&lt;date&gt;";
1802
			from "&lt;date&gt;";
1803
			to "&lt;date&gt;";
1804
		};
1805
	};
1806
	multihop {
1807
		interval &lt;time&gt;;
1808
		min rx interval &lt;time&gt;;
1809
		min tx interval &lt;time&gt;;
1810
		idle tx interval &lt;time&gt;;
1811
		multiplier &lt;num&gt;;
1812
		passive &lt;switch&gt;;
1813
	};
1814
	neighbor &lt;ip&gt; [dev "&lt;interface&gt;"] [local &lt;ip&gt;] [multihop &lt;switch&gt;];
1815
}
1816
</code>
1817

    
1818
<descrip>
1819
	<tag><label id="bfd-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
1820
	Interface definitions allow to specify options for sessions associated
1821
	with such interfaces and also may contain interface specific options.
1822
	See <ref id="proto-iface" name="interface"> common option for a detailed
1823
	description of interface patterns. Note that contrary to the behavior of
1824
	<cf/interface/ definitions of other protocols, BFD protocol would accept
1825
	sessions (in default configuration) even on interfaces not covered by
1826
	such definitions.
1827

    
1828
	<tag><label id="bfd-multihop">multihop { <m/options/ }</tag>
1829
	Multihop definitions allow to specify options for multihop BFD sessions,
1830
	in the same manner as <cf/interface/ definitions are used for directly
1831
	connected sessions. Currently only one such definition (for all multihop
1832
	sessions) could be used.
1833

    
1834
	<tag><label id="bfd-neighbor">neighbor <m/ip/ [dev "<m/interface/"] [local <m/ip/] [multihop <m/switch/]</tag>
1835
	BFD sessions are usually created on demand as requested by other
1836
	protocols (like OSPF or BGP). This option allows to explicitly add
1837
	a BFD session to the specified neighbor regardless of such requests.
1838

    
1839
	The session is identified by the IP address of the neighbor, with
1840
	optional specification of used interface and local IP. By default
1841
	the neighbor must be directly connected, unless the session is
1842
	configured as multihop. Note that local IP must be specified for
1843
	multihop sessions.
1844
</descrip>
1845

    
1846
<p>Session specific options (part of <cf/interface/ and <cf/multihop/ definitions):
1847

    
1848
<descrip>
1849
	<tag><label id="bfd-interval">interval <m/time/</tag>
1850
	BFD ensures availability of the forwarding path associated with the
1851
	session by periodically sending BFD control packets in both
1852
	directions. The rate of such packets is controlled by two options,
1853
	<cf/min rx interval/ and <cf/min tx interval/ (see below). This option
1854
	is just a shorthand to set both of these options together.
1855

    
1856
	<tag><label id="bfd-min-rx-interval">min rx interval <m/time/</tag>
1857
	This option specifies the minimum RX interval, which is announced to the
1858
	neighbor and used there to limit the neighbor's rate of generated BFD
1859
	control packets. Default: 10 ms.
1860

    
1861
	<tag><label id="bfd-min-tx-interval">min tx interval <m/time/</tag>
1862
	This option specifies the desired TX interval, which controls the rate
1863
	of generated BFD control packets (together with <cf/min rx interval/
1864
	announced by the neighbor). Note that this value is used only if the BFD
1865
	session is up, otherwise the value of <cf/idle tx interval/ is used
1866
	instead. Default: 100 ms.
1867

    
1868
	<tag><label id="bfd-idle-tx-interval">idle tx interval <m/time/</tag>
1869
	In order to limit unnecessary traffic in cases where a neighbor is not
1870
	available or not running BFD, the rate of generated BFD control packets
1871
	is lower when the BFD session is not up. This option specifies the
1872
	desired TX interval in such cases instead of <cf/min tx interval/.
1873
	Default: 1 s.
1874

    
1875
	<tag><label id="bfd-multiplier">multiplier <m/num/</tag>
1876
	Failure detection time for BFD sessions is based on established rate of
1877
	BFD control packets (<cf>min rx/tx interval</cf>) multiplied by this
1878
	multiplier, which is essentially (ignoring jitter) a number of missed
1879
	packets after which the session is declared down. Note that rates and
1880
	multipliers could be different in each direction of a BFD session.
1881
	Default: 5.
1882

    
1883
	<tag><label id="bfd-passive">passive <m/switch/</tag>
1884
	Generally, both BFD session endpoints try to establish the session by
1885
	sending control packets to the other side. This option allows to enable
1886
	passive mode, which means that the router does not send BFD packets
1887
	until it has received one from the other side. Default: disabled.
1888

    
1889
	<tag>authentication none</tag>
1890
	No passwords are sent in BFD packets. This is the default value.
1891

    
1892
	<tag>authentication simple</tag>
1893
	Every packet carries 16 bytes of password. Received packets lacking this
1894
	password are ignored. This authentication mechanism is very weak.
1895

    
1896
	<tag>authentication [meticulous] keyed md5|sha1</tag>
1897
	An authentication code is appended to each packet. The cryptographic
1898
	algorithm is keyed MD5 or keyed SHA-1. Note that the algorithm is common
1899
	for all keys (on one interface), in contrast to OSPF or RIP, where it
1900
	is a per-key option. Passwords (keys) are not sent open via network.
1901

    
1902
	The <cf/meticulous/ variant means that cryptographic sequence numbers
1903
	are increased for each sent packet, while in the basic variant they are
1904
	increased about once per second. Generally, the <cf/meticulous/ variant
1905
	offers better resistance to replay attacks but may require more
1906
	computation.
1907

    
1908
	<tag>password "<M>text</M>"</tag>
1909
	Specifies a password used for authentication. See <ref id="dsc-pass"
1910
	name="password"> common option for detailed description. Note that
1911
	password option <cf/algorithm/ is not available in BFD protocol. The
1912
	algorithm is selected by <cf/authentication/ option for all passwords.
1913

    
1914
</descrip>
1915

    
1916
<sect1>Example
1917
<label id="bfd-exam">
1918

    
1919
<p><code>
1920
protocol bfd {
1921
	interface "eth*" {
1922
		min rx interval 20 ms;
1923
		min tx interval 50 ms;
1924
		idle tx interval 300 ms;
1925
	};
1926
	interface "gre*" {
1927
		interval 200 ms;
1928
		multiplier 10;
1929
		passive;
1930
	};
1931
	multihop {
1932
		interval 200 ms;
1933
		multiplier 10;
1934
	};
1935

    
1936
	neighbor 192.168.1.10;
1937
	neighbor 192.168.2.2 dev "eth2";
1938
	neighbor 192.168.10.1 local 192.168.1.1 multihop;
1939
}
1940
</code>
1941

    
1942

    
1943
<sect>BGP
1944
<label id="bgp">
1945

    
1946
<p>The Border Gateway Protocol is the routing protocol used for backbone level
1947
routing in the today's Internet. Contrary to other protocols, its convergence
1948
does not rely on all routers following the same rules for route selection,
1949
making it possible to implement any routing policy at any router in the network,
1950
the only restriction being that if a router advertises a route, it must accept
1951
and forward packets according to it.
1952

    
1953
<p>BGP works in terms of autonomous systems (often abbreviated as AS). Each AS
1954
is a part of the network with common management and common routing policy. It is
1955
identified by a unique 16-bit number (ASN). Routers within each AS usually
1956
exchange AS-internal routing information with each other using an interior
1957
gateway protocol (IGP, such as OSPF or RIP). Boundary routers at the border of
1958
the AS communicate global (inter-AS) network reachability information with their
1959
neighbors in the neighboring AS'es via exterior BGP (eBGP) and redistribute
1960
received information to other routers in the AS via interior BGP (iBGP).
1961

    
1962
<p>Each BGP router sends to its neighbors updates of the parts of its routing
1963
table it wishes to export along with complete path information (a list of AS'es
1964
the packet will travel through if it uses the particular route) in order to
1965
avoid routing loops.
1966

    
1967
<sect1>Supported standards:
1968
<label id="bgp-standards">
1969

    
1970
<itemize>
1971
<item> <rfc id="4271"> - Border Gateway Protocol 4 (BGP)
1972
<item> <rfc id="1997"> - BGP Communities Attribute
1973
<item> <rfc id="2385"> - Protection of BGP Sessions via TCP MD5 Signature
1974
<item> <rfc id="2545"> - Use of BGP Multiprotocol Extensions for IPv6
1975
<item> <rfc id="2918"> - Route Refresh Capability
1976
<item> <rfc id="3107"> - Carrying Label Information in BGP
1977
<item> <rfc id="4360"> - BGP Extended Communities Attribute
1978
<item> <rfc id="4364"> - BGP/MPLS IPv4 Virtual Private Networks
1979
<item> <rfc id="4456"> - BGP Route Reflection
1980
<item> <rfc id="4486"> - Subcodes for BGP Cease Notification Message
1981
<item> <rfc id="4659"> - BGP/MPLS IPv6 Virtual Private Networks
1982
<item> <rfc id="4724"> - Graceful Restart Mechanism for BGP
1983
<item> <rfc id="4760"> - Multiprotocol extensions for BGP
1984
<item> <rfc id="4798"> - Connecting IPv6 Islands over IPv4 MPLS
1985
<item> <rfc id="5065"> - AS confederations for BGP
1986
<item> <rfc id="5082"> - Generalized TTL Security Mechanism
1987
<item> <rfc id="5492"> - Capabilities Advertisement with BGP
1988
<item> <rfc id="5549"> - Advertising IPv4 NLRI with an IPv6 Next Hop
1989
<item> <rfc id="5575"> - Dissemination of Flow Specification Rules
1990
<item> <rfc id="5668"> - 4-Octet AS Specific BGP Extended Community
1991
<item> <rfc id="6286"> - AS-Wide Unique BGP Identifier
1992
<item> <rfc id="6608"> - Subcodes for BGP Finite State Machine Error
1993
<item> <rfc id="6793"> - BGP Support for 4-Octet AS Numbers
1994
<item> <rfc id="7313"> - Enhanced Route Refresh Capability for BGP
1995
<item> <rfc id="7606"> - Revised Error Handling for BGP UPDATE Messages
1996
<item> <rfc id="7911"> - Advertisement of Multiple Paths in BGP
1997
<item> <rfc id="7947"> - Internet Exchange BGP Route Server
1998
<item> <rfc id="8092"> - BGP Large Communities Attribute
1999
</itemize>
2000

    
2001
<sect1>Route selection rules
2002
<label id="bgp-route-select-rules">
2003

    
2004
<p>BGP doesn't have any simple metric, so the rules for selection of an optimal
2005
route among multiple BGP routes with the same preference are a bit more complex
2006
and they are implemented according to the following algorithm. It starts the
2007
first rule, if there are more "best" routes, then it uses the second rule to
2008
choose among them and so on.
2009

    
2010
<itemize>
2011
	<item>Prefer route with the highest Local Preference attribute.
2012
	<item>Prefer route with the shortest AS path.
2013
	<item>Prefer IGP origin over EGP and EGP origin over incomplete.
2014
	<item>Prefer the lowest value of the Multiple Exit Discriminator.
2015
	<item>Prefer routes received via eBGP over ones received via iBGP.
2016
	<item>Prefer routes with lower internal distance to a boundary router.
2017
	<item>Prefer the route with the lowest value of router ID of the
2018
	advertising router.
2019
</itemize>
2020

    
2021
<sect1>IGP routing table
2022
<label id="bgp-igp-routing-table">
2023

    
2024
<p>BGP is mainly concerned with global network reachability and with routes to
2025
other autonomous systems. When such routes are redistributed to routers in the
2026
AS via BGP, they contain IP addresses of a boundary routers (in route attribute
2027
NEXT_HOP). BGP depends on existing IGP routing table with AS-internal routes to
2028
determine immediate next hops for routes and to know their internal distances to
2029
boundary routers for the purpose of BGP route selection. In BIRD, there is
2030
usually one routing table used for both IGP routes and BGP routes.
2031

    
2032
<sect1>Configuration
2033
<label id="bgp-config">
2034

    
2035
<p>Each instance of the BGP corresponds to one neighboring router. This allows
2036
to set routing policy and all the other parameters differently for each neighbor
2037
using the following configuration parameters:
2038

    
2039
<descrip>
2040
	<tag><label id="bgp-local">local [<m/ip/] as <m/number/</tag>
2041
	Define which AS we are part of. (Note that contrary to other IP routers,
2042
	BIRD is able to act as a router located in multiple AS'es simultaneously,
2043
	but in such cases you need to tweak the BGP paths manually in the filters
2044
	to get consistent behavior.) Optional <cf/ip/ argument specifies a source
2045
	address, equivalent to the <cf/source address/ option (see below). This
2046
	parameter is mandatory.
2047

    
2048
	<tag><label id="bgp-neighbor">neighbor [<m/ip/] [port <m/number/] [as <m/number/]</tag>
2049
	Define neighboring router this instance will be talking to and what AS
2050
	it is located in. In case the neighbor is in the same AS as we are, we
2051
	automatically switch to iBGP. Optionally, the remote port may also be
2052
	specified. The parameter may be used multiple times with different
2053
	sub-options (e.g., both <cf/neighbor 10.0.0.1 as 65000;/ and
2054
	<cf/neighbor 10.0.0.1; neighbor as 65000;/ are valid). This parameter is
2055
	mandatory.
2056

    
2057
	<tag><label id="bgp-iface">interface <m/string/</tag>
2058
	Define interface we should use for link-local BGP IPv6 sessions.
2059
	Interface can also be specified as a part of <cf/neighbor address/
2060
	(e.g., <cf/neighbor fe80::1234%eth0 as 65000;/). It is an error to use
2061
	this parameter for non link-local sessions.
2062

    
2063
	<tag><label id="bgp-direct">direct</tag>
2064
	Specify that the neighbor is directly connected. The IP address of the
2065
	neighbor must be from a directly reachable IP range (i.e. associated
2066
	with one of your router's interfaces), otherwise the BGP session
2067
	wouldn't start but it would wait for such interface to appear. The
2068
	alternative is the <cf/multihop/ option. Default: enabled for eBGP.
2069

    
2070
	<tag><label id="bgp-multihop">multihop [<m/number/]</tag>
2071
	Configure multihop BGP session to a neighbor that isn't directly
2072
	connected. Accurately, this option should be used if the configured
2073
	neighbor IP address does not match with any local network subnets. Such
2074
	IP address have to be reachable through system routing table. The
2075
	alternative is the <cf/direct/ option. For multihop BGP it is
2076
	recommended to explicitly configure the source address to have it
2077
	stable. Optional <cf/number/ argument can be used to specify the number
2078
	of hops (used for TTL). Note that the number of networks (edges) in a
2079
	path is counted; i.e., if two BGP speakers are separated by one router,
2080
	the number of hops is 2. Default: enabled for iBGP.
2081

    
2082
	<tag><label id="bgp-source-address">source address <m/ip/</tag>
2083
	Define local address we should use for next hop calculation and as a
2084
	source address for the BGP session. Default: the address of the local
2085
	end of the interface our neighbor is connected to.
2086

    
2087
	<tag><label id="bgp-strict-bind">strict bind <m/switch/</tag>
2088
	Specify whether BGP listening socket should be bound to a specific local
2089
	address (the same as the <cf/source address/) and associated interface,
2090
	or to all addresses. Binding to a specific address could be useful in
2091
	cases like running multiple BIRD instances on a machine, each using its
2092
	IP address. Note that listening sockets bound to a specific address and
2093
	to all addresses collide, therefore either all BGP protocols (of the
2094
	same address family and using the same local port) should have set
2095
	<cf/strict bind/, or none of them. Default: disabled.
2096

    
2097
	<tag><label id="bgp-next-hop-self">next hop self</tag>
2098
	Avoid calculation of the Next Hop attribute and always advertise our own
2099
	source address as a next hop. This needs to be used only occasionally to
2100
	circumvent misconfigurations of other routers. Default: disabled.
2101

    
2102
	<tag><label id="bgp-next-hop-keep">next hop keep</tag>
2103
	Forward the received Next Hop attribute even in situations where the
2104
	local address should be used instead, like when the route is sent to an
2105
	interface with a different subnet. Default: disabled.
2106

    
2107
	<tag><label id="bgp-missing-lladdr">missing lladdr self|drop|ignore</tag>
2108
	Next Hop attribute in BGP-IPv6 sometimes contains just the global IPv6
2109
	address, but sometimes it has to contain both global and link-local IPv6
2110
	addresses. This option specifies what to do if BIRD have to send both
2111
	addresses but does not know link-local address. This situation might
2112
	happen when routes from other protocols are exported to BGP, or when
2113
	improper updates are received from BGP peers. <cf/self/ means that BIRD
2114
	advertises its own local address instead. <cf/drop/ means that BIRD
2115
	skips that prefixes and logs error. <cf/ignore/ means that BIRD ignores
2116
	the problem and sends just the global address (and therefore forms
2117
	improper BGP update). Default: <cf/self/, unless BIRD is configured as a
2118
	route server (option <cf/rs client/), in that case default is <cf/ignore/,
2119
	because route servers usually do not forward packets themselves.
2120

    
2121
	<tag><label id="bgp-gateway">gateway direct|recursive</tag>
2122
	For received routes, their <cf/gw/ (immediate next hop) attribute is
2123
	computed from received <cf/bgp_next_hop/ attribute. This option
2124
	specifies how it is computed. Direct mode means that the IP address from
2125
	<cf/bgp_next_hop/ is used if it is directly reachable, otherwise the
2126
	neighbor IP address is used. Recursive mode means that the gateway is
2127
	computed by an IGP routing table lookup for the IP address from
2128
	<cf/bgp_next_hop/. Note that there is just one level of indirection in
2129
	recursive mode - the route obtained by the lookup must not be recursive
2130
	itself, to prevent mutually recursive routes.
2131

    
2132
	Recursive mode is the behavior specified by the BGP
2133
	standard. Direct mode is simpler, does not require any routes in a
2134
	routing table, and was used in older versions of BIRD, but does not
2135
	handle well nontrivial iBGP setups and multihop. Recursive mode is
2136
	incompatible with <ref id="dsc-table-sorted" name="sorted tables">. Default:
2137
	<cf/direct/ for direct sessions, <cf/recursive/ for multihop sessions.
2138

    
2139
	<tag><label id="bgp-igp-table">igp table <m/name/</tag>
2140
	Specifies a table that is used as an IGP routing table. Default: the
2141
	same as the table BGP is connected to.
2142

    
2143
	<tag><label id="bgp-check-link">check link <M>switch</M></tag>
2144
	BGP could use hardware link state into consideration.  If enabled,
2145
	BIRD tracks the link state of the associated interface and when link
2146
	disappears (e.g. an ethernet cable is unplugged), the BGP session is
2147
	immediately shut down. Note that this option cannot be used with
2148
	multihop BGP. Default: disabled.
2149

    
2150
	<tag><label id="bgp-bfd">bfd <M>switch</M></tag>
2151
	BGP could use BFD protocol as an advisory mechanism for neighbor
2152
	liveness and failure detection. If enabled, BIRD setups a BFD session
2153
	for the BGP neighbor and tracks its liveness by it. This has an
2154
	advantage of an order of magnitude lower detection times in case of
2155
	failure. Note that BFD protocol also has to be configured, see
2156
	<ref id="bfd" name="BFD"> section for details. Default: disabled.
2157

    
2158
	<tag><label id="bgp-ttl-security">ttl security <m/switch/</tag>
2159
	Use GTSM (<rfc id="5082"> - the generalized TTL security mechanism). GTSM
2160
	protects against spoofed packets by ignoring received packets with a
2161
	smaller than expected TTL. To work properly, GTSM have to be enabled on
2162
	both sides of a BGP session. If both <cf/ttl security/ and
2163
	<cf/multihop/ options are enabled, <cf/multihop/ option should specify
2164
	proper hop value to compute expected TTL. Kernel support required:
2165
	Linux: 2.6.34+ (IPv4), 2.6.35+ (IPv6), BSD: since long ago, IPv4 only.
2166
	Note that full (ICMP protection, for example) <rfc id="5082"> support is
2167
	provided by Linux only. Default: disabled.
2168

    
2169
	<tag><label id="bgp-password">password <m/string/</tag>
2170
	Use this password for MD5 authentication of BGP sessions (<rfc id="2385">). When
2171
	used on BSD systems, see also <cf/setkey/ option below. Default: no
2172
	authentication.
2173

    
2174
	<tag><label id="bgp-setkey">setkey <m/switch/</tag>
2175
	On BSD systems, keys for TCP MD5 authentication are stored in the global
2176
	SA/SP database, which can be accessed by external utilities (e.g.
2177
	setkey(8)). BIRD configures security associations in the SA/SP database
2178
	automatically based on <cf/password/ options (see above), this option
2179
	allows to disable automatic updates by BIRD when manual configuration by
2180
	external utilities is preferred. Note that automatic SA/SP database
2181
	updates are currently implemented only for FreeBSD. Passwords have to be
2182
	set manually by an external utility on NetBSD and OpenBSD. Default:
2183
	enabled (ignored on non-FreeBSD).
2184

    
2185
	<tag><label id="bgp-passive">passive <m/switch/</tag>
2186
	Standard BGP behavior is both initiating outgoing connections and
2187
	accepting incoming connections. In passive mode, outgoing connections
2188
	are not initiated. Default: off.
2189

    
2190
	<tag><label id="bgp-confederation">confederation <m/number/</tag>
2191
	BGP confederations (<rfc id="5065">) are collections of autonomous
2192
	systems that act as one entity to external systems, represented by one
2193
	confederation identifier (instead of AS numbers). This option allows to
2194
	enable BGP confederation behavior and to specify the local confederation
2195
	identifier. When BGP confederations are used, all BGP speakers that are
2196
	members of the BGP confederation should have the same confederation
2197
	identifier configured. Default: 0 (no confederation).
2198

    
2199
	<tag><label id="bgp-confederation-member">confederation member <m/switch/</tag>
2200
	When BGP confederations are used, this option allows to specify whether
2201
	the BGP neighbor is a member of the same confederation as the local BGP
2202
	speaker. The option is unnecessary (and ignored) for IBGP sessions, as
2203
	the same AS number implies the same confederation. Default: no.
2204

    
2205
	<tag><label id="bgp-rr-client">rr client</tag>
2206
	Be a route reflector and treat the neighbor as a route reflection
2207
	client. Default: disabled.
2208

    
2209
	<tag><label id="bgp-rr-cluster-id">rr cluster id <m/IPv4 address/</tag>
2210
	Route reflectors use cluster id to avoid route reflection loops. When
2211
	there is one route reflector in a cluster it usually uses its router id
2212
	as a cluster id, but when there are more route reflectors in a cluster,
2213
	these need to be configured (using this option) to use a common cluster
2214
	id. Clients in a cluster need not know their cluster id and this option
2215
	is not allowed for them. Default: the same as router id.
2216

    
2217
	<tag><label id="bgp-rs-client">rs client</tag>
2218
	Be a route server and treat the neighbor as a route server client.
2219
	A route server is used as a replacement for full mesh EBGP routing in
2220
	Internet exchange points in a similar way to route reflectors used in
2221
	IBGP routing. BIRD does not implement obsoleted <rfc id="1863">, but
2222
	uses ad-hoc implementation, which behaves like plain EBGP but reduces
2223
	modifications to advertised route attributes to be transparent (for
2224
	example does not prepend its AS number to AS PATH attribute and
2225
	keeps MED attribute). Default: disabled.
2226

    
2227
	<tag><label id="bgp-secondary">secondary <m/switch/</tag>
2228
	Usually, if an export filter rejects a selected route, no other route is
2229
	propagated for that network. This option allows to try the next route in
2230
	order until one that is accepted is found or all routes for that network
2231
	are rejected. This can be used for route servers that need to propagate
2232
	different tables to each client but do not want to have these tables
2233
	explicitly (to conserve memory). This option requires that the connected
2234
	routing table is <ref id="dsc-table-sorted" name="sorted">. Default: off.
2235

    
2236
	<tag><label id="bgp-add-paths">add paths <m/switch/|rx|tx</tag>
2237
	Standard BGP can propagate only one path (route) per destination network
2238
	(usually the selected one). This option controls the add-path protocol
2239
	extension, which allows to advertise any number of paths to a
2240
	destination. Note that to be active, add-path has to be enabled on both
2241
	sides of the BGP session, but it could be enabled separately for RX and
2242
	TX direction. When active, all available routes accepted by the export
2243
	filter are advertised to the neighbor. Default: off.
2244

    
2245
	<tag><label id="bgp-allow-local-as">allow local as [<m/number/]</tag>
2246
	BGP prevents routing loops by rejecting received routes with the local
2247
	AS number in the AS path. This option allows to loose or disable the
2248
	check. Optional <cf/number/ argument can be used to specify the maximum
2249
	number of local ASNs in the AS path that is allowed for received
2250
	routes. When the option is used without the argument, the check is
2251
	completely disabled and you should ensure loop-free behavior by some
2252
	other means. Default: 0 (no local AS number allowed).
2253

    
2254
	<tag><label id="bgp-enable-route-refresh">enable route refresh <m/switch/</tag>
2255
	After the initial route exchange, BGP protocol uses incremental updates
2256
	to keep BGP speakers synchronized. Sometimes (e.g., if BGP speaker
2257
	changes its import filter, or if there is suspicion of inconsistency) it
2258
	is necessary to do a new complete route exchange. BGP protocol extension
2259
	Route Refresh (<rfc id="2918">) allows BGP speaker to request
2260
	re-advertisement of all routes from its neighbor. BGP protocol
2261
	extension Enhanced Route Refresh (<rfc id="7313">) specifies explicit
2262
	begin and end for such exchanges, therefore the receiver can remove
2263
	stale routes that were not advertised during the exchange. This option
2264
	specifies whether BIRD advertises these capabilities and supports
2265
	related procedures. Note that even when disabled, BIRD can send route
2266
	refresh requests.  Default: on.
2267

    
2268
	<tag><label id="bgp-graceful-restart">graceful restart <m/switch/|aware</tag>
2269
	When a BGP speaker restarts or crashes, neighbors will discard all
2270
	received paths from the speaker, which disrupts packet forwarding even
2271
	when the forwarding plane of the speaker remains intact. <rfc
2272
	id="4724"> specifies an optional graceful restart mechanism to
2273
	alleviate this issue. This option controls the mechanism. It has three
2274
	states: Disabled, when no support is provided. Aware, when the graceful
2275
	restart support is announced and the support for restarting neighbors
2276
	is provided, but no local graceful restart is allowed (i.e.
2277
	receiving-only role). Enabled, when the full graceful restart
2278
	support is provided (i.e. both restarting and receiving role). Note
2279
	that proper support for local graceful restart requires also
2280
	configuration of other protocols.  Default: aware.
2281

    
2282
	<tag><label id="bgp-graceful-restart-time">graceful restart time <m/number/</tag>
2283
	The restart time is announced in the BGP graceful restart capability
2284
	and specifies how long the neighbor would wait for the BGP session to
2285
	re-establish after a restart before deleting stale routes. Default:
2286
	120 seconds.
2287

    
2288
	<tag><label id="bgp-interpret-communities">interpret communities <m/switch/</tag>
2289
	<rfc id="1997"> demands that BGP speaker should process well-known
2290
	communities like no-export (65535, 65281) or no-advertise (65535,
2291
	65282). For example, received route carrying a no-adverise community
2292
	should not be advertised to any of its neighbors. If this option is
2293
	enabled (which is by default), BIRD has such behavior automatically (it
2294
	is evaluated when a route is exported to the BGP protocol just before
2295
	the export filter).  Otherwise, this integrated processing of
2296
	well-known communities is disabled. In that case, similar behavior can
2297
	be implemented in the export filter.  Default: on.
2298

    
2299
	<tag><label id="bgp-enable-as4">enable as4 <m/switch/</tag>
2300
	BGP protocol was designed to use 2B AS numbers and was extended later to
2301
	allow 4B AS number. BIRD supports 4B AS extension, but by disabling this
2302
	option it can be persuaded not to advertise it and to maintain old-style
2303
	sessions with its neighbors. This might be useful for circumventing bugs
2304
	in neighbor's implementation of 4B AS extension. Even when disabled
2305
	(off), BIRD behaves internally as AS4-aware BGP router. Default: on.
2306

    
2307
	<tag><label id="bgp-enable-extended-messages">enable extended messages <m/switch/</tag>
2308
	The BGP protocol uses maximum message length of 4096 bytes. This option
2309
	provides an extension to allow extended messages with length up
2310
	to 65535 bytes. Default: off.
2311

    
2312
	<tag><label id="bgp-capabilities">capabilities <m/switch/</tag>
2313
	Use capability advertisement to advertise optional capabilities. This is
2314
	standard behavior for newer BGP implementations, but there might be some
2315
	older BGP implementations that reject such connection attempts. When
2316
	disabled (off), features that request it (4B AS support) are also
2317
	disabled. Default: on, with automatic fallback to off when received
2318
	capability-related error.
2319

    
2320
	<tag><label id="bgp-advertise-ipv4">advertise ipv4 <m/switch/</tag>
2321
	Advertise IPv4 multiprotocol capability. This is not a correct behavior
2322
	according to the strict interpretation of <rfc id="4760">, but it is
2323
	widespread and required by some BGP implementations (Cisco and Quagga).
2324
	This option is relevant to IPv4 mode with enabled capability
2325
	advertisement only. Default: on.
2326

    
2327
	<tag><label id="bgp-disable-after-error">disable after error <m/switch/</tag>
2328
	When an error is encountered (either locally or by the other side),
2329
	disable the instance automatically and wait for an administrator to fix
2330
	the problem manually. Default: off.
2331

    
2332
	<tag><label id="bgp-hold-time">hold time <m/number/</tag>
2333
	Time in seconds to wait for a Keepalive message from the other side
2334
	before considering the connection stale. Default: depends on agreement
2335
	with the neighboring router, we prefer 240 seconds if the other side is
2336
	willing to accept it.
2337

    
2338
	<tag><label id="bgp-startup-hold-time">startup hold time <m/number/</tag>
2339
	Value of the hold timer used before the routers have a chance to exchange
2340
	open messages and agree on the real value. Default: 240	seconds.
2341

    
2342
	<tag><label id="bgp-keepalive-time">keepalive time <m/number/</tag>
2343
	Delay in seconds between sending of two consecutive Keepalive messages.
2344
	Default: One third of the hold time.
2345

    
2346
	<tag><label id="bgp-connect-delay-time">connect delay time <m/number/</tag>
2347
	Delay in seconds between protocol startup and the first attempt to
2348
	connect. Default: 5 seconds.
2349

    
2350
	<tag><label id="bgp-connect-retry-time">connect retry time <m/number/</tag>
2351
	Time in seconds to wait before retrying a failed attempt to connect.
2352
	Default: 120 seconds.
2353

    
2354
	<tag><label id="bgp-error-wait-time">error wait time <m/number/,<m/number/</tag>
2355
	Minimum and maximum delay in seconds between a protocol failure (either
2356
	local or reported by the peer) and automatic restart. Doesn't apply
2357
	when <cf/disable after error/ is configured. If consecutive errors
2358
	happen, the delay is increased exponentially until it reaches the
2359
	maximum. Default: 60, 300.
2360

    
2361
	<tag><label id="bgp-error-forget-time">error forget time <m/number/</tag>
2362
	Maximum time in seconds between two protocol failures to treat them as a
2363
	error sequence which makes <cf/error wait time/ increase exponentially.
2364
	Default: 300 seconds.
2365

    
2366
	<tag><label id="bgp-path-metric">path metric <m/switch/</tag>
2367
	Enable comparison of path lengths when deciding which BGP route is the
2368
	best one. Default: on.
2369

    
2370
	<tag><label id="bgp-med-metric">med metric <m/switch/</tag>
2371
	Enable comparison of MED attributes (during best route selection) even
2372
	between routes received from different ASes. This may be useful if all
2373
	MED attributes contain some consistent metric, perhaps enforced in
2374
	import filters of AS boundary routers. If this option is disabled, MED
2375
	attributes are compared only if routes are received from the same AS
2376
	(which is the standard behavior). Default: off.
2377

    
2378
	<tag><label id="bgp-deterministic-med">deterministic med <m/switch/</tag>
2379
	BGP route selection algorithm is often viewed as a comparison between
2380
	individual routes (e.g. if a new route appears and is better than the
2381
	current best one, it is chosen as the new best one). But the proper
2382
	route selection, as specified by <rfc id="4271">, cannot be fully
2383
	implemented in that way. The problem is mainly in handling the MED
2384
	attribute. BIRD, by default, uses an simplification based on individual
2385
	route comparison, which in some cases may lead to temporally dependent
2386
	behavior (i.e. the selection is dependent on the order in which routes
2387
	appeared). This option enables a different (and slower) algorithm
2388
	implementing proper <rfc id="4271"> route selection, which is
2389
	deterministic. Alternative way how to get deterministic behavior is to
2390
	use <cf/med metric/ option. This option is incompatible with <ref
2391
	id="dsc-table-sorted" name="sorted tables">.  Default: off.
2392

    
2393
	<tag><label id="bgp-igp-metric">igp metric <m/switch/</tag>
2394
	Enable comparison of internal distances to boundary routers during best
2395
 	route selection. Default: on.
2396

    
2397
	<tag><label id="bgp-prefer-older">prefer older <m/switch/</tag>
2398
	Standard route selection algorithm breaks ties by comparing router IDs.
2399
	This changes the behavior to prefer older routes (when both are external
2400
	and from different peer). For details, see <rfc id="5004">. Default: off.
2401

    
2402
	<tag><label id="bgp-default-med">default bgp_med <m/number/</tag>
2403
	Value of the Multiple Exit Discriminator to be used during route
2404
	selection when the MED attribute is missing. Default: 0.
2405

    
2406
	<tag><label id="bgp-default-local-pref">default bgp_local_pref <m/number/</tag>
2407
	A default value for the Local Preference attribute. It is used when
2408
	a new Local Preference attribute is attached to a route by the BGP
2409
	protocol itself (for example, if a route is received through eBGP and
2410
	therefore does not have such attribute). Default: 100 (0 in pre-1.2.0
2411
	versions of BIRD).
2412
</descrip>
2413

    
2414
<sect1>Attributes
2415
<label id="bgp-attr">
2416

    
2417
<p>BGP defines several route attributes. Some of them (those marked with
2418
`<tt/I/' in the table below) are available on internal BGP connections only,
2419
some of them (marked with `<tt/O/') are optional.
2420

    
2421
<descrip>
2422
	<tag><label id="rta-bgp-path">bgppath bgp_path/</tag>
2423
	Sequence of AS numbers describing the AS path the packet will travel
2424
	through when forwarded according to the particular route. In case of
2425
	internal BGP it doesn't contain the number of the local AS.
2426

    
2427
	<tag><label id="rta-bgp-local-pref">int bgp_local_pref/ [I]</tag>
2428
	Local preference value used for selection among multiple BGP routes (see
2429
	the selection rules above). It's used as an additional metric which is
2430
	propagated through the whole local AS.
2431

    
2432
	<tag><label id="rta-bgp-med">int bgp_med/ [O]</tag>
2433
	The Multiple Exit Discriminator of the route is an optional attribute
2434
	which is used on external (inter-AS) links to convey to an adjacent AS
2435
	the optimal entry point into the local AS. The received attribute is
2436
	also propagated over internal BGP links. The attribute value is zeroed
2437
	when a route is exported to an external BGP instance to ensure that the
2438
	attribute received from a neighboring AS is not propagated to other
2439
	neighboring ASes. A new value might be set in the export filter of an
2440
	external BGP instance. See <rfc id="4451"> for further discussion of
2441
	BGP MED attribute.
2442

    
2443
	<tag><label id="rta-bgp-origin">enum bgp_origin/</tag>
2444
	Origin of the route: either <cf/ORIGIN_IGP/ if the route has originated
2445
	in an interior routing protocol or <cf/ORIGIN_EGP/ if it's been imported
2446
	from the <tt>EGP</tt> protocol (nowadays it seems to be obsolete) or
2447
	<cf/ORIGIN_INCOMPLETE/ if the origin is unknown.
2448

    
2449
	<tag><label id="rta-bgp-next-hop">ip bgp_next_hop/</tag>
2450
	Next hop to be used for forwarding of packets to this destination. On
2451
	internal BGP connections, it's an address of the originating router if
2452
	it's inside the local AS or a boundary router the packet will leave the
2453
	AS through if it's an exterior route, so each BGP speaker within the AS
2454
	has a chance to use the shortest interior path possible to this point.
2455

    
2456
	<tag><label id="rta-bgp-atomic-aggr">void bgp_atomic_aggr/ [O]</tag>
2457
	This is an optional attribute which carries no value, but the sole
2458
	presence of which indicates that the route has been aggregated from
2459
	multiple routes by some router on the path from the originator.
2460

    
2461
<!-- we don't handle aggregators right since they are of a very obscure type
2462
	<tag>bgp_aggregator</tag>
2463
-->
2464
	<tag><label id="rta-bgp-community">clist bgp_community/ [O]</tag>
2465
	List of community values associated with the route. Each such value is a
2466
	pair (represented as a <cf/pair/ data type inside the filters) of 16-bit
2467
	integers, the first of them containing the number of the AS which
2468
	defines the community and the second one being a per-AS identifier.
2469
	There are lots of uses of the community mechanism, but generally they
2470
	are used to carry policy information like "don't export to USA peers".
2471
	As each AS can define its own routing policy, it also has a complete
2472
	freedom about which community attributes it defines and what will their
2473
	semantics be.
2474

    
2475
	<tag><label id="rta-bgp-ext-community">eclist bgp_ext_community/ [O]</tag>
2476
	List of extended community values associated with the route. Extended
2477
	communities have similar usage as plain communities, but they have an
2478
	extended range (to allow 4B ASNs) and a nontrivial structure with a type
2479
	field. Individual community values are represented using an <cf/ec/ data
2480
	type inside the filters.
2481

    
2482
	<tag><label id="rta-bgp-large-community">lclist <cf/bgp_large_community/ [O]</tag>
2483
	List of large community values associated with the route. Large BGP
2484
	communities is another variant of communities, but contrary to extended
2485
	communities they behave very much the same way as regular communities,
2486
	just larger -- they are uniform untyped triplets of 32bit numbers.
2487
	Individual community values are represented using an <cf/lc/ data type
2488
	inside the filters.
2489

    
2490
	<tag><label id="rta-bgp-originator-id">quad bgp_originator_id/ [I, O]</tag>
2491
	This attribute is created by the route reflector when reflecting the
2492
	route and contains the router ID of the originator of the route in the
2493
	local AS.
2494

    
2495
	<tag><label id="rta-bgp-cluster-list">clist bgp_cluster_list/ [I, O]</tag>
2496
	This attribute contains a list of cluster IDs of route reflectors. Each
2497
	route reflector prepends its cluster ID when reflecting the route.
2498
</descrip>
2499

    
2500
<sect1>Example
2501
<label id="bgp-exam">
2502

    
2503
<p><code>
2504
protocol bgp {
2505
	local as 65000;			     # Use a private AS number
2506
	neighbor 198.51.100.130 as 64496;    # Our neighbor ...
2507
	multihop;			     # ... which is connected indirectly
2508
	export filter {			     # We use non-trivial export rules
2509
		if source = RTS_STATIC then { # Export only static routes
2510
			# Assign our community
2511
			bgp_community.add((65000,64501));
2512
			# Artificially increase path length
2513
			# by advertising local AS number twice
2514
			if bgp_path ~ [= 65000 =] then
2515
				bgp_path.prepend(65000);
2516
			accept;
2517
		}
2518
		reject;
2519
	};
2520
	import all;
2521
	source address 198.51.100.14;	# Use a non-standard source address
2522
}
2523
</code>
2524

    
2525

    
2526
<sect>Device
2527
<label id="device">
2528

    
2529
<p>The Device protocol is not a real routing protocol. It doesn't generate any
2530
routes and it only serves as a module for getting information about network
2531
interfaces from the kernel.
2532

    
2533
<p>Except for very unusual circumstances, you probably should include this
2534
protocol in the configuration since almost all other protocols require network
2535
interfaces to be defined for them to work with.
2536

    
2537
<sect1>Configuration
2538
<label id="device-config">
2539

    
2540
<p><descrip>
2541

    
2542
	<tag><label id="device-scan-time">scan time <m/number/</tag>
2543
	Time in seconds between two scans of the network interface list. On
2544
	systems where we are notified about interface status changes
2545
	asynchronously (such as newer versions of Linux), we need to scan the
2546
	list only in order to avoid confusion by lost notification messages,
2547
	so the default time is set to a large value.
2548

    
2549
	<tag><label id="device-primary">primary [ "<m/mask/" ] <m/prefix/</tag>
2550
	If a network interface has more than one network address, BIRD has to
2551
	choose one of them as a primary one. By default, BIRD chooses the
2552
	lexicographically smallest address as the primary one.
2553

    
2554
	This option allows to specify which network address should be chosen as
2555
	a primary one. Network addresses that match <m/prefix/ are preferred to
2556
	non-matching addresses. If more <cf/primary/ options are used, the first
2557
	one has the highest preference. If "<m/mask/" is specified, then such
2558
	<cf/primary/ option is relevant only to matching network interfaces.
2559

    
2560
	In all cases, an address marked by operating system as secondary cannot
2561
	be chosen as the primary one.
2562
</descrip>
2563

    
2564
<p>As the Device protocol doesn't generate any routes, it cannot have
2565
any attributes. Example configuration looks like this:
2566

    
2567
<p><code>
2568
protocol device {
2569
	scan time 10;		# Scan the interfaces often
2570
	primary "eth0" 192.168.1.1;
2571
	primary 192.168.0.0/16;
2572
}
2573
</code>
2574

    
2575

    
2576
<sect>Direct
2577
<label id="direct">
2578

    
2579
<p>The Direct protocol is a simple generator of device routes for all the
2580
directly connected networks according to the list of interfaces provided by the
2581
kernel via the Device protocol.
2582

    
2583
<p>The question is whether it is a good idea to have such device routes in BIRD
2584
routing table. OS kernel usually handles device routes for directly connected
2585
networks by itself so we don't need (and don't want) to export these routes to
2586
the kernel protocol. OSPF protocol creates device routes for its interfaces
2587
itself and BGP protocol is usually used for exporting aggregate routes. Although
2588
there are some use cases that use the direct protocol (like abusing eBGP as an
2589
IGP routing protocol), in most cases it is not needed to have these device
2590
routes in BIRD routing table and to use the direct protocol.
2591

    
2592
<p>There is one notable case when you definitely want to use the direct protocol
2593
-- running BIRD on BSD systems. Having high priority device routes for directly
2594
connected networks from the direct protocol protects kernel device routes from
2595
being overwritten or removed by IGP routes during some transient network
2596
conditions, because a lower priority IGP route for the same network is not
2597
exported to the kernel routing table. This is an issue on BSD systems only, as
2598
on Linux systems BIRD cannot change non-BIRD route in the kernel routing table.
2599

    
2600
<p>There are just few configuration options for the Direct protocol:
2601

    
2602
<p><descrip>
2603
	<tag><label id="direct-iface">interface <m/pattern/ [, <m/.../]</tag>
2604
	By default, the Direct protocol will generate device routes for all the
2605
	interfaces available. If you want to restrict it to some subset of
2606
	interfaces or addresses (e.g. if you're using multiple routing tables
2607
	for policy routing and some of the policy domains don't contain all
2608
	interfaces), just use this clause. See <ref id="proto-iface" name="interface">
2609
	common option for detailed description. The Direct protocol uses
2610
	extended interface clauses.
2611

    
2612
	<tag><label id="direct-check-link">check link <m/switch/</tag>
2613
	If enabled, a hardware link state (reported by OS) is taken into
2614
	consideration. Routes for directly connected networks are generated only
2615
	if link up is reported and they are withdrawn when link disappears
2616
	(e.g., an ethernet cable is unplugged). Default value is no.
2617
</descrip>
2618

    
2619
<p>Direct device routes don't contain any specific attributes.
2620

    
2621
<p>Example config might look like this:
2622

    
2623
<p><code>
2624
protocol direct {
2625
	interface "-arc*", "*";		# Exclude the ARCnets
2626
}
2627
</code>
2628

    
2629

    
2630
<sect>Kernel
2631
<label id="krt">
2632

    
2633
<p>The Kernel protocol is not a real routing protocol. Instead of communicating
2634
with other routers in the network, it performs synchronization of BIRD's routing
2635
tables with the OS kernel. Basically, it sends all routing table updates to the
2636
kernel and from time to time it scans the kernel tables to see whether some
2637
routes have disappeared (for example due to unnoticed up/down transition of an
2638
interface) or whether an `alien' route has been added by someone else (depending
2639
on the <cf/learn/ switch, such routes are either ignored or accepted to our
2640
table).
2641

    
2642
<p>Unfortunately, there is one thing that makes the routing table synchronization
2643
a bit more complicated. In the kernel routing table there are also device routes
2644
for directly connected networks. These routes are usually managed by OS itself
2645
(as a part of IP address configuration) and we don't want to touch that. They
2646
are completely ignored during the scan of the kernel tables and also the export
2647
of device routes from BIRD tables to kernel routing tables is restricted to
2648
prevent accidental interference. This restriction can be disabled using
2649
<cf/device routes/ switch.
2650

    
2651
<p>If your OS supports only a single routing table, you can configure only one
2652
instance of the Kernel protocol. If it supports multiple tables (in order to
2653
allow policy routing; such an OS is for example Linux), you can run as many
2654
instances as you want, but each of them must be connected to a different BIRD
2655
routing table and to a different kernel table.
2656

    
2657
<p>Because the kernel protocol is partially integrated with the connected
2658
routing table, there are two limitations - it is not possible to connect more
2659
kernel protocols to the same routing table and changing route destination
2660
(gateway) in an export filter of a kernel protocol does not work. Both
2661
limitations can be overcome using another routing table and the pipe protocol.
2662

    
2663
<sect1>Configuration
2664
<label id="krt-config">
2665

    
2666
<p><descrip>
2667
	<tag><label id="krt-persist">persist <m/switch/</tag>
2668
	Tell BIRD to leave all its routes in the routing tables when it exits
2669
	(instead of cleaning them up).
2670

    
2671
	<tag><label id="krt-scan-time">scan time <m/number/</tag>
2672
	Time in seconds between two consecutive scans of the kernel routing
2673
	table.
2674

    
2675
	<tag><label id="krt-learn">learn <m/switch/</tag>
2676
	Enable learning of routes added to the kernel routing tables by other
2677
	routing daemons or by the system administrator. This is possible only on
2678
	systems which support identification of route authorship.
2679

    
2680
	<tag><label id="krt-device-routes">device routes <m/switch/</tag>
2681
	Enable export of device routes to the kernel routing table. By default,
2682
	such routes are rejected (with the exception of explicitly configured
2683
	device routes from the static protocol) regardless of the export filter
2684
	to protect device routes in kernel routing table (managed by OS itself)
2685
	from accidental overwriting or erasing.
2686

    
2687
	<tag><label id="krt-kernel-table">kernel table <m/number/</tag>
2688
	Select which kernel table should this particular instance of the Kernel
2689
	protocol work with. Available only on systems supporting multiple
2690
	routing tables.
2691

    
2692
	<tag><label id="krt-metric">metric <m/number/</tag> (Linux)
2693
	Use specified value as a kernel metric (priority) for all routes sent to
2694
	the kernel. When multiple routes for the same network are in the kernel
2695
	routing table, the Linux kernel chooses one with lower metric. Also,
2696
	routes with different metrics do not clash with each other, therefore
2697
	using dedicated metric value is a reliable way to avoid overwriting
2698
	routes from other sources (e.g. kernel device routes). Metric 0 has a
2699
	special meaning of undefined metric, in which either OS default is used,
2700
	or per-route metric can be set using <cf/krt_metric/ attribute. Default:
2701
	0 (undefined).
2702

    
2703
	<tag><label id="krt-graceful-restart">graceful restart <m/switch/</tag>
2704
	Participate in graceful restart recovery. If this option is enabled and
2705
	a graceful restart recovery is active, the Kernel protocol will defer
2706
	synchronization of routing tables until the end of the recovery. Note
2707
	that import of kernel routes to BIRD is not affected.
2708

    
2709
	<tag><label id="krt-merge-paths">merge paths <M>switch</M> [limit <M>number</M>]</tag>
2710
	Usually, only best routes are exported to the kernel protocol. With path
2711
	merging enabled, both best routes and equivalent non-best routes are
2712
	merged during export to generate one ECMP (equal-cost multipath) route
2713
	for each network. This is useful e.g. for BGP multipath. Note that best
2714
	routes are still pivotal for route export (responsible for most
2715
	properties of resulting ECMP routes), while exported non-best routes are
2716
	responsible just for additional multipath next hops. This option also
2717
	allows to specify a limit on maximal number of nexthops in one route. By
2718
	default, multipath merging is disabled. If enabled, default value of the
2719
	limit is 16.
2720
</descrip>
2721

    
2722
<sect1>Attributes
2723
<label id="krt-attr">
2724

    
2725
<p>The Kernel protocol defines several attributes. These attributes are
2726
translated to appropriate system (and OS-specific) route attributes. We support
2727
these attributes:
2728

    
2729
<descrip>
2730
	<tag><label id="rta-krt-source">int krt_source/</tag>
2731
	The original source of the imported kernel route. The value is
2732
	system-dependent. On Linux, it is a value of the protocol field of the
2733
	route. See /etc/iproute2/rt_protos for common values. On BSD, it is
2734
	based on STATIC and PROTOx flags. The attribute is read-only.
2735

    
2736
	<tag><label id="rta-krt-metric">int krt_metric/</tag> (Linux)
2737
	The kernel metric of the route. When multiple same routes are in a
2738
	kernel routing table, the Linux kernel chooses one with lower metric.
2739
	Note that preferred way to set kernel metric is to use protocol option
2740
	<cf/metric/, unless per-route metric values are needed.
2741

    
2742
	<tag><label id="rta-krt-prefsrc">ip krt_prefsrc/</tag> (Linux)
2743
	The preferred source address. Used in source address selection for
2744
	outgoing packets. Has to be one of the IP addresses of the router.
2745

    
2746
	<tag><label id="rta-krt-realm">int krt_realm/</tag> (Linux)
2747
	The realm of the route. Can be used for traffic classification.
2748

    
2749
	<tag><label id="rta-krt-scope">int krt_scope/</tag> (Linux IPv4)
2750
	The scope of the route. Valid values are 0-254, although Linux kernel
2751
	may reject some values depending on route type and nexthop. It is
2752
	supposed to represent `indirectness' of the route, where nexthops of
2753
	routes are resolved through routes with a higher scope, but in current
2754
	kernels anything below <it/link/ (253) is treated as <it/global/ (0).
2755
	When not present, global scope is implied for all routes except device
2756
	routes, where link scope is used by default.
2757
</descrip>
2758

    
2759
<p>In Linux, there is also a plenty of obscure route attributes mostly focused
2760
on tuning TCP performance of local connections. BIRD supports most of these
2761
attributes, see Linux or iproute2 documentation for their meaning. Attributes
2762
<cf/krt_lock_*/ and <cf/krt_feature_*/ have type bool, others have type int.
2763
Supported attributes are:
2764

    
2765
<cf/krt_mtu/, <cf/krt_lock_mtu/, <cf/krt_window/, <cf/krt_lock_window/,
2766
<cf/krt_rtt/, <cf/krt_lock_rtt/, <cf/krt_rttvar/, <cf/krt_lock_rttvar/,
2767
<cf/krt_sstresh/, <cf/krt_lock_sstresh/, <cf/krt_cwnd/, <cf/krt_lock_cwnd/,
2768
<cf/krt_advmss/, <cf/krt_lock_advmss/, <cf/krt_reordering/, <cf/krt_lock_reordering/,
2769
<cf/krt_hoplimit/, <cf/krt_lock_hoplimit/, <cf/krt_rto_min/, <cf/krt_lock_rto_min/,
2770
<cf/krt_initcwnd/, <cf/krt_initrwnd/, <cf/krt_quickack/,
2771
<cf/krt_feature_ecn/, <cf/krt_feature_allfrag/
2772

    
2773
<sect1>Example
2774
<label id="krt-exam">
2775

    
2776
<p>A simple configuration can look this way:
2777

    
2778
<p><code>
2779
protocol kernel {
2780
	export all;
2781
}
2782
</code>
2783

    
2784
<p>Or for a system with two routing tables:
2785

    
2786
<p><code>
2787
protocol kernel {		# Primary routing table
2788
	learn;			# Learn alien routes from the kernel
2789
	persist;		# Don't remove routes on bird shutdown
2790
	scan time 10;		# Scan kernel routing table every 10 seconds
2791
	import all;
2792
	export all;
2793
}
2794

    
2795
protocol kernel {		# Secondary routing table
2796
	table auxtable;
2797
	kernel table 100;
2798
	export all;
2799
}
2800
</code>
2801

    
2802

    
2803
<sect>OSPF
2804
<label id="ospf">
2805

    
2806
<sect1>Introduction
2807
<label id="ospf-intro">
2808

    
2809
<p>Open Shortest Path First (OSPF) is a quite complex interior gateway
2810
protocol. The current IPv4 version (OSPFv2) is defined in <rfc id="2328"> and
2811
the current IPv6 version (OSPFv3) is defined in <rfc id="5340"> It's a link
2812
state (a.k.a. shortest path first) protocol -- each router maintains a database
2813
describing the autonomous system's topology. Each participating router has an
2814
identical copy of the database and all routers run the same algorithm
2815
calculating a shortest path tree with themselves as a root. OSPF chooses the
2816
least cost path as the best path.
2817

    
2818
<p>In OSPF, the autonomous system can be split to several areas in order to
2819
reduce the amount of resources consumed for exchanging the routing information
2820
and to protect the other areas from incorrect routing data. Topology of the area
2821
is hidden to the rest of the autonomous system.
2822

    
2823
<p>Another very important feature of OSPF is that it can keep routing information
2824
from other protocols (like Static or BGP) in its link state database as external
2825
routes. Each external route can be tagged by the advertising router, making it
2826
possible to pass additional information between routers on the boundary of the
2827
autonomous system.
2828

    
2829
<p>OSPF quickly detects topological changes in the autonomous system (such as
2830
router interface failures) and calculates new loop-free routes after a short
2831
period of convergence. Only a minimal amount of routing traffic is involved.
2832

    
2833
<p>Each router participating in OSPF routing periodically sends Hello messages
2834
to all its interfaces. This allows neighbors to be discovered dynamically. Then
2835
the neighbors exchange theirs parts of the link state database and keep it
2836
identical by flooding updates. The flooding process is reliable and ensures that
2837
each router detects all changes.
2838

    
2839
<sect1>Configuration
2840
<label id="ospf-config">
2841

    
2842
<p>First, the desired OSPF version can be specified by using <cf/ospf v2/ or
2843
<cf/ospf v3/ as a protocol type. By default, OSPFv2 is used. In the main part of
2844
configuration, there can be multiple definitions of OSPF areas, each with a
2845
different id. These definitions includes many other switches and multiple
2846
definitions of interfaces. Definition of interface may contain many switches and
2847
constant definitions and list of neighbors on nonbroadcast networks.
2848

    
2849
<code>
2850
protocol ospf [v2|v3] &lt;name&gt; {
2851
	rfc1583compat &lt;switch&gt;;
2852
	instance id &lt;num&gt;;
2853
	stub router &lt;switch&gt;;
2854
	tick &lt;num&gt;;
2855
	ecmp &lt;switch&gt; [limit &lt;num&gt;];
2856
	merge external &lt;switch&gt;;
2857
	area &lt;id&gt; {
2858
		stub;
2859
		nssa;
2860
		summary &lt;switch&gt;;
2861
		default nssa &lt;switch&gt;;
2862
		default cost &lt;num&gt;;
2863
		default cost2 &lt;num&gt;;
2864
		translator &lt;switch&gt;;
2865
		translator stability &lt;num&gt;;
2866

    
2867
                networks {
2868
			&lt;prefix&gt;;
2869
			&lt;prefix&gt; hidden;
2870
		}
2871
                external {
2872
			&lt;prefix&gt;;
2873
			&lt;prefix&gt; hidden;
2874
			&lt;prefix&gt; tag &lt;num&gt;;
2875
		}
2876
		stubnet &lt;prefix&gt;;
2877
		stubnet &lt;prefix&gt; {
2878
			hidden &lt;switch&gt;;
2879
			summary &lt;switch&gt;;
2880
			cost &lt;num&gt;;
2881
		}
2882
		interface &lt;interface pattern&gt; [instance &lt;num&gt;] {
2883
			cost &lt;num&gt;;
2884
			stub &lt;switch&gt;;
2885
			hello &lt;num&gt;;
2886
			poll &lt;num&gt;;
2887
			retransmit &lt;num&gt;;
2888
			priority &lt;num&gt;;
2889
			wait &lt;num&gt;;
2890
			dead count &lt;num&gt;;
2891
			dead &lt;num&gt;;
2892
			secondary &lt;switch&gt;;
2893
			rx buffer [normal|large|&lt;num&gt;];
2894
			tx length &lt;num&gt;;
2895
			type [broadcast|bcast|pointopoint|ptp|
2896
				nonbroadcast|nbma|pointomultipoint|ptmp];
2897
			link lsa suppression &lt;switch&gt;;
2898
			strict nonbroadcast &lt;switch&gt;;
2899
			real broadcast &lt;switch&gt;;
2900
			ptp netmask &lt;switch&gt;;
2901
			check link &lt;switch&gt;;
2902
			bfd &lt;switch&gt;;
2903
			ecmp weight &lt;num&gt;;
2904
			ttl security [&lt;switch&gt;; | tx only]
2905
			tx class|dscp &lt;num&gt;;
2906
			tx priority &lt;num&gt;;
2907
			authentication none|simple|cryptographic;
2908
			password "&lt;text&gt;";
2909
			password "&lt;text&gt;" {
2910
				id &lt;num&gt;;
2911
				generate from "&lt;date&gt;";
2912
				generate to "&lt;date&gt;";
2913
				accept from "&lt;date&gt;";
2914
				accept to "&lt;date&gt;";
2915
				from "&lt;date&gt;";
2916
				to "&lt;date&gt;";
2917
				algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
2918
			};
2919
			neighbors {
2920
				&lt;ip&gt;;
2921
				&lt;ip&gt; eligible;
2922
			};
2923
		};
2924
		virtual link &lt;id&gt; [instance &lt;num&gt;] {
2925
			hello &lt;num&gt;;
2926
			retransmit &lt;num&gt;;
2927
			wait &lt;num&gt;;
2928
			dead count &lt;num&gt;;
2929
			dead &lt;num&gt;;
2930
			authentication none|simple|cryptographic;
2931
			password "&lt;text&gt;";
2932
			password "&lt;text&gt;" {
2933
				id &lt;num&gt;;
2934
				generate from "&lt;date&gt;";
2935
				generate to "&lt;date&gt;";
2936
				accept from "&lt;date&gt;";
2937
				accept to "&lt;date&gt;";
2938
				from "&lt;date&gt;";
2939
				to "&lt;date&gt;";
2940
				algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
2941
			};
2942
		};
2943
	};
2944
}
2945
</code>
2946

    
2947
<descrip>
2948
	<tag><label id="ospf-rfc1583compat">rfc1583compat <M>switch</M></tag>
2949
	This option controls compatibility of routing table calculation with
2950
	<rfc id="1583">. Default value is no.
2951

    
2952
	<tag><label id="ospf-instance-id">instance id <m/num/</tag>
2953
	When multiple OSPF protocol instances are active on the same links, they
2954
	should use different instance IDs to distinguish their packets. Although
2955
	it could be done on per-interface basis, it is often preferred to set
2956
	one instance ID to whole OSPF domain/topology (e.g., when multiple
2957
	instances are used to represent separate logical topologies on the same
2958
	physical network). This option specifies the default instance ID for all
2959
	interfaces of the OSPF instance. Note that this option, if used, must
2960
	precede interface definitions. Default value is 0.
2961

    
2962
	<tag><label id="ospf-stub-router">stub router <M>switch</M></tag>
2963
	This option configures the router to be a stub router, i.e., a router
2964
	that participates in the OSPF topology but does not allow transit
2965
	traffic. In OSPFv2, this is implemented by advertising maximum metric
2966
	for outgoing links. In OSPFv3, the stub router behavior is announced by
2967
	clearing the R-bit in the router LSA. See <rfc id="6987"> for details.
2968
	Default value is no.
2969

    
2970
	<tag><label id="ospf-tick">tick <M>num</M></tag>
2971
	The routing table calculation and clean-up of areas' databases is not
2972
	performed when a single link state change arrives. To lower the CPU
2973
	utilization, it's processed later at periodical intervals of <m/num/
2974
	seconds. The default value is 1.
2975

    
2976
	<tag><label id="ospf-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
2977
	This option specifies whether OSPF is allowed to generate ECMP
2978
	(equal-cost multipath) routes. Such routes are used when there are
2979
	several directions to the destination, each with the same (computed)
2980
	cost. This option also allows to specify a limit on maximum number of
2981
	nexthops in one route. By default, ECMP is disabled. If enabled,
2982
	default	value of the limit is 16.
2983

    
2984
	<tag><label id="ospf-merge-external">merge external <M>switch</M></tag>
2985
	This option specifies whether OSPF should merge external routes from
2986
	different routers/LSAs for the same destination. When enabled together
2987
	with <cf/ecmp/, equal-cost external routes will be combined to multipath
2988
	routes in the same way as regular routes. When disabled, external routes
2989
	from different LSAs are treated as separate even if they represents the
2990
	same destination. Default value is no.
2991

    
2992
	<tag><label id="ospf-area">area <M>id</M></tag>
2993
	This defines an OSPF area with given area ID (an integer or an IPv4
2994
	address, similarly to a router ID). The most important area is the
2995
	backbone (ID 0) to which every other area must be connected.
2996

    
2997
	<tag><label id="ospf-stub">stub</tag>
2998
	This option configures the area to be a stub area. External routes are
2999
	not flooded into stub areas. Also summary LSAs can be limited in stub
3000
	areas (see option <cf/summary/). By default, the area is not a stub
3001
	area.
3002

    
3003
	<tag><label id="ospf-nssa">nssa</tag>
3004
	This option configures the area to be a NSSA (Not-So-Stubby Area). NSSA
3005
	is a variant of a stub area which allows a limited way of external route
3006
	propagation. Global external routes are not propagated into a NSSA, but
3007
	an external route can be imported into NSSA as a (area-wide) NSSA-LSA
3008
	(and possibly translated and/or aggregated on area boundary). By
3009
	default, the area is not NSSA.
3010

    
3011
	<tag><label id="ospf-summary">summary <M>switch</M></tag>
3012
	This option controls propagation of summary LSAs into stub or NSSA
3013
	areas. If enabled, summary LSAs are propagated as usual, otherwise just
3014
	the default summary route (0.0.0.0/0) is propagated (this is sometimes
3015
	called totally stubby area). If a stub area has more area boundary
3016
	routers, propagating summary LSAs could lead to more efficient routing
3017
	at the cost of larger link state database. Default value is no.
3018

    
3019
	<tag><label id="ospf-default-nssa">default nssa <M>switch</M></tag>
3020
	When <cf/summary/ option is enabled, default summary route is no longer
3021
	propagated to the NSSA. In that case, this option allows to originate
3022
	default route as NSSA-LSA to the NSSA. Default value is no.
3023

    
3024
	<tag><label id="ospf-default-cost">default cost <M>num</M></tag>
3025
	This option controls the cost of a default route propagated to stub and
3026
	NSSA areas. Default value is 1000.
3027

    
3028
	<tag><label id="ospf-default-cost2">default cost2 <M>num</M></tag>
3029
	When a default route is originated as NSSA-LSA, its cost can use either
3030
	type 1 or type 2 metric. This option allows to specify the cost of a
3031
	default route in type 2 metric. By default, type 1 metric (option
3032
	<cf/default cost/) is used.
3033

    
3034
	<tag><label id="ospf-translator">translator <M>switch</M></tag>
3035
	This option controls translation of NSSA-LSAs into external LSAs. By
3036
	default, one translator per NSSA is automatically elected from area
3037
	boundary routers. If enabled, this area boundary router would
3038
	unconditionally translate all NSSA-LSAs regardless of translator
3039
	election. Default value is no.
3040

    
3041
	<tag><label id="ospf-translator-stability">translator stability <M>num</M></tag>
3042
	This option controls the translator stability interval (in seconds).
3043
	When the new translator is elected, the old one keeps translating until
3044
	the interval is over. Default value is 40.
3045

    
3046
	<tag><label id="ospf-networks">networks { <m/set/ }</tag>
3047
	Definition of area IP ranges. This is used in summary LSA origination.
3048
	Hidden networks are not propagated into other areas.
3049

    
3050
	<tag><label id="ospf-external">external { <m/set/ }</tag>
3051
	Definition of external area IP ranges for NSSAs. This is used for
3052
	NSSA-LSA translation. Hidden networks are not translated into external
3053
	LSAs. Networks can have configured route tag.
3054

    
3055
	<tag><label id="ospf-stubnet">stubnet <m/prefix/ { <m/options/ }</tag>
3056
	Stub networks are networks that are not transit networks between OSPF
3057
	routers. They are also propagated through an OSPF area as a part of a
3058
	link state database. By default, BIRD generates a stub network record
3059
	for each primary network address on each OSPF interface that does not
3060
	have any OSPF neighbors, and also for each non-primary network address
3061
	on each OSPF interface. This option allows to alter a set of stub
3062
	networks propagated by this router.
3063

    
3064
	Each instance of this option adds a stub network with given network
3065
	prefix to the set of propagated stub network, unless option <cf/hidden/
3066
	is used. It also suppresses default stub networks for given network
3067
	prefix. When option <cf/summary/ is used, also default stub networks
3068
	that are subnetworks of given stub network are suppressed. This might be
3069
	used, for example, to aggregate generated stub networks.
3070

    
3071
	<tag><label id="ospf-iface">interface <M>pattern</M> [instance <m/num/]</tag>
3072
	Defines that the specified interfaces belong to the area being defined.
3073
	See <ref id="proto-iface" name="interface"> common option for detailed
3074
	description. In OSPFv2, extended interface clauses are used, because
3075
	each network prefix is handled as a separate virtual interface.
3076

    
3077
	You can specify alternative instance ID for the interface definition,
3078
	therefore it is possible to have several instances of that interface
3079
	with different options or even in different areas. For OSPFv2, instance
3080
	ID support is an extension (<rfc id="6549">) and is supposed to be set
3081
	per-protocol. For OSPFv3, it is an integral feature.
3082

    
3083
	<tag><label id="ospf-virtual-link">virtual link <M>id</M> [instance <m/num/]</tag>
3084
	Virtual link to router with the router id. Virtual link acts as a
3085
	point-to-point interface belonging to backbone. The actual area is used
3086
	as a transport area. This item cannot be in the backbone. Like with
3087
	<cf/interface/ option, you could also use several virtual links to one
3088
	destination with different instance IDs.
3089

    
3090
	<tag><label id="ospf-cost">cost <M>num</M></tag>
3091
	Specifies output cost (metric) of an interface. Default value is 10.
3092

    
3093
	<tag><label id="ospf-stub-iface">stub <M>switch</M></tag>
3094
	If set to interface it does not listen to any packet and does not send
3095
	any hello. Default value is no.
3096

    
3097
	<tag><label id="ospf-hello">hello <M>num</M></tag>
3098
	Specifies interval in seconds between sending of Hello messages. Beware,
3099
	all routers on the same network need to have the same hello interval.
3100
	Default value is 10.
3101

    
3102
	<tag><label id="ospf-poll">poll <M>num</M></tag>
3103
	Specifies interval in seconds between sending of Hello messages for some
3104
	neighbors on NBMA network. Default value is 20.
3105

    
3106
	<tag><label id="ospf-retransmit">retransmit <M>num</M></tag>
3107
	Specifies interval in seconds between retransmissions of unacknowledged
3108
	updates. Default value is 5.
3109

    
3110
	<tag><label id="ospf-priority">priority <M>num</M></tag>
3111
	On every multiple access network (e.g., the Ethernet) Designated Router
3112
	and Backup Designated router are elected. These routers have some special
3113
	functions in the flooding process. Higher priority increases preferences
3114
	in this election. Routers with priority 0 are not eligible. Default
3115
	value is 1.
3116

    
3117
	<tag><label id="ospf-wait">wait <M>num</M></tag>
3118
	After start, router waits for the specified number of seconds between
3119
	starting election and building adjacency. Default value is 4*<m/hello/.
3120

    
3121
	<tag><label id="ospf-dead-count">dead count <M>num</M></tag>
3122
	When the router does not receive any messages from a neighbor in
3123
	<m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
3124

    
3125
	<tag><label id="ospf-dead">dead <M>num</M></tag>
3126
	When the router does not receive any messages from a neighbor in
3127
	<m/dead/ seconds, it will consider the neighbor down. If both directives
3128
	<cf/dead count/ and <cf/dead/ are used, <cf/dead/ has precedence.
3129

    
3130
	<tag><label id="ospf-secondary">secondary <M>switch</M></tag>
3131
	On BSD systems, older versions of BIRD supported OSPFv2 only for the
3132
	primary IP address of an interface, other IP ranges on the interface
3133
	were handled as stub networks. Since v1.4.1, regular operation on
3134
	secondary IP addresses is supported, but disabled by default for
3135
	compatibility. This option allows to enable it. The option is a
3136
	transitional measure, will be removed in the next major release as the
3137
	behavior will be changed. On Linux systems, the option is irrelevant, as
3138
	operation on non-primary addresses is already the regular behavior.
3139

    
3140
	<tag><label id="ospf-rx-buffer">rx buffer <M>num</M></tag>
3141
	This option allows to specify the size of buffers used for packet
3142
	processing. The buffer size should be bigger than maximal size of any
3143
	packets. By default, buffers are dynamically resized as needed, but a
3144
	fixed value could be specified. Value <cf/large/ means maximal allowed
3145
	packet size - 65535.
3146

    
3147
	<tag><label id="ospf-tx-length">tx length <M>num</M></tag>
3148
	Transmitted OSPF messages that contain large amount of information are
3149
	segmented to separate OSPF packets to avoid IP fragmentation. This
3150
	option specifies the soft ceiling for the length of generated OSPF
3151
	packets. Default value is the MTU of the network interface. Note that
3152
	larger OSPF packets may still be generated if underlying OSPF messages
3153
	cannot be splitted (e.g. when one large LSA is propagated).
3154

    
3155
	<tag><label id="ospf-type-bcast">type broadcast|bcast</tag>
3156
	BIRD detects a type of a connected network automatically, but sometimes
3157
	it's convenient to force use of a different type manually. On broadcast
3158
	networks (like ethernet), flooding and Hello messages are sent using
3159
	multicasts (a single packet for all the neighbors). A designated router
3160
	is elected and it is responsible for synchronizing the link-state
3161
	databases and originating network LSAs. This network type cannot be used
3162
	on physically NBMA networks and on unnumbered networks (networks without
3163
	proper IP prefix).
3164

    
3165
	<tag><label id="ospf-type-ptp">type pointopoint|ptp</tag>
3166
	Point-to-point networks connect just 2 routers together. No election is
3167
	performed and no network LSA is originated, which makes it simpler and
3168
	faster to establish. This network type is useful not only for physically
3169
	PtP ifaces (like PPP or tunnels), but also for broadcast networks used
3170
	as PtP links. This network type cannot be used on physically NBMA
3171
	networks.
3172

    
3173
	<tag><label id="ospf-type-nbma">type nonbroadcast|nbma</tag>
3174
	On NBMA networks, the packets are sent to each neighbor separately
3175
	because of lack of multicast capabilities. Like on broadcast networks,
3176
	a designated router is elected, which plays a central role in propagation
3177
	of LSAs. This network type cannot be used on unnumbered networks.
3178

    
3179
	<tag><label id="ospf-type-ptmp">type pointomultipoint|ptmp</tag>
3180
	This is another network type designed to handle NBMA networks. In this
3181
	case the NBMA network is treated as a collection of PtP links. This is
3182
	useful if not every pair of routers on the NBMA network has direct
3183
	communication, or if the NBMA network is used as an (possibly
3184
	unnumbered) PtP link.
3185

    
3186
	<tag><label id="ospf-link-lsa-suppression">link lsa suppression <m/switch/</tag>
3187
	In OSPFv3, link LSAs are generated for each link, announcing link-local
3188
	IPv6 address of the router to its local neighbors. These are useless on
3189
	PtP or PtMP networks and this option allows to suppress the link LSA
3190
	origination for such interfaces. The option is ignored on other than PtP
3191
	or PtMP interfaces. Default value is no.
3192

    
3193
	<tag><label id="ospf-strict-nonbroadcast">strict nonbroadcast <m/switch/</tag>
3194
	If set, don't send hello to any undefined neighbor. This switch is
3195
	ignored on other than NBMA or PtMP interfaces. Default value is no.
3196

    
3197
	<tag><label id="ospf-real-broadcast">real broadcast <m/switch/</tag>
3198
	In <cf/type broadcast/ or <cf/type ptp/ network configuration, OSPF
3199
	packets are sent as IP multicast packets. This option changes the
3200
	behavior to using old-fashioned IP broadcast packets. This may be useful
3201
	as a workaround if IP multicast for some reason does not work or does
3202
	not work reliably. This is a non-standard option and probably is not
3203
	interoperable with other OSPF implementations. Default value is no.
3204

    
3205
	<tag><label id="ospf-ptp-netmask">ptp netmask <m/switch/</tag>
3206
	In <cf/type ptp/ network configurations, OSPFv2 implementations should
3207
	ignore received netmask field in hello packets and should send hello
3208
	packets with zero netmask field on unnumbered PtP links. But some OSPFv2
3209
	implementations perform netmask checking even for PtP links. This option
3210
	specifies whether real netmask will be used in hello packets on <cf/type
3211
 	ptp/ interfaces. You should ignore this option unless you meet some
3212
	compatibility problems related to this issue. Default value is no for
3213
	unnumbered PtP links, yes otherwise.
3214

    
3215
	<tag><label id="ospf-check-link">check link <M>switch</M></tag>
3216
	If set, a hardware link state (reported by OS) is taken into consideration.
3217
	When a link disappears (e.g. an ethernet cable is unplugged), neighbors
3218
	are immediately considered unreachable and only the address of the iface
3219
	(instead of whole network prefix) is propagated. It is possible that
3220
	some hardware drivers or platforms do not implement this feature.
3221
	Default value is no.
3222

    
3223
	<tag><label id="ospf-bfd">bfd <M>switch</M></tag>
3224
	OSPF could use BFD protocol as an advisory mechanism for neighbor
3225
	liveness and failure detection. If enabled, BIRD setups a BFD session
3226
	for each OSPF neighbor and tracks its liveness by it. This has an
3227
	advantage of an order of magnitude lower detection times in case of
3228
	failure. Note that BFD protocol also has to be configured, see
3229
	<ref id="bfd" name="BFD"> section for details. Default value is no.
3230

    
3231
	<tag><label id="ospf-ttl-security">ttl security [<m/switch/ | tx only]</tag>
3232
	TTL security is a feature that protects routing protocols from remote
3233
	spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
3234
	destined to neighbors. Because TTL is decremented when packets are
3235
	forwarded, it is non-trivial to spoof packets with TTL 255 from remote
3236
	locations. Note that this option would interfere with OSPF virtual
3237
	links.
3238

    
3239
	If this option is enabled, the router will send OSPF packets with TTL
3240
	255 and drop received packets with TTL less than 255. If this option si
3241
	set to <cf/tx only/, TTL 255 is used for sent packets, but is not
3242
	checked for received packets. Default value is no.
3243

    
3244
	<tag><label id="ospf-tx-class">tx class|dscp|priority <m/num/</tag>
3245
	These options specify the ToS/DiffServ/Traffic class/Priority of the
3246
	outgoing OSPF packets. See <ref id="proto-tx-class" name="tx class"> common
3247
	option for detailed description.
3248

    
3249
	<tag><label id="ospf-ecmp-weight">ecmp weight <M>num</M></tag>
3250
	When ECMP (multipath) routes are allowed, this value specifies a
3251
	relative weight used for nexthops going through the iface. Allowed
3252
	values are 1-256. Default value is 1.
3253

    
3254
	<tag><label id="ospf-auth-none">authentication none</tag>
3255
	No passwords are sent in OSPF packets. This is the default value.
3256

    
3257
	<tag><label id="ospf-auth-simple">authentication simple</tag>
3258
	Every packet carries 8 bytes of password. Received packets lacking this
3259
	password are ignored. This authentication mechanism is very weak.
3260
	This option is not available in OSPFv3.
3261

    
3262
	<tag><label id="ospf-auth-cryptographic">authentication cryptographic</tag>
3263
	An authentication code is appended to every packet. The specific
3264
	cryptographic algorithm is selected by option <cf/algorithm/ for each
3265
	key. The default cryptographic algorithm for OSPFv2 keys is Keyed-MD5
3266
	and for OSPFv3 keys is HMAC-SHA-256. Passwords are not sent open via
3267
	network, so this mechanism is quite secure. Packets can still be read by
3268
	an attacker.
3269

    
3270
	<tag><label id="ospf-pass">password "<M>text</M>"</tag>
3271
	Specifies a password used for authentication. See
3272
	<ref id="proto-pass" name="password"> common option for detailed
3273
	description.
3274

    
3275
	<tag><label id="ospf-neighbors">neighbors { <m/set/ } </tag>
3276
	A set of neighbors to which Hello messages on NBMA or PtMP networks are
3277
	to be sent. For NBMA networks, some of them could be marked as eligible.
3278
	In OSPFv3, link-local addresses should be used, using global ones is
3279
	possible, but it is nonstandard and might be problematic. And definitely,
3280
	link-local and global addresses should not be mixed.
3281
</descrip>
3282

    
3283
<sect1>Attributes
3284
<label id="ospf-attr">
3285

    
3286
<p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
3287

    
3288
<p>Metric is ranging from 1 to infinity (65535). External routes use
3289
<cf/metric type 1/ or <cf/metric type 2/. A <cf/metric of type 1/ is comparable
3290
with internal <cf/metric/, a <cf/metric of type 2/ is always longer than any
3291
<cf/metric of type 1/ or any <cf/internal metric/. <cf/Internal metric/ or
3292
<cf/metric of type 1/ is stored in attribute <cf/ospf_metric1/, <cf/metric type
3293
2/ is stored in attribute <cf/ospf_metric2/. If you specify both metrics only
3294
metric1 is used.
3295

    
3296
<p>Each external route can also carry attribute <cf/ospf_tag/ which is a 32-bit
3297
integer which is used when exporting routes to other protocols; otherwise, it
3298
doesn't affect routing inside the OSPF domain at all. The fourth attribute
3299
<cf/ospf_router_id/ is a router ID of the router advertising that route /
3300
network. This attribute is read-only. Default is <cf/ospf_metric2 = 10000/ and
3301
<cf/ospf_tag = 0/.
3302

    
3303
<sect1>Example
3304
<label id="ospf-exam">
3305

    
3306
<p><code>
3307
protocol ospf MyOSPF {
3308
	rfc1583compat yes;
3309
	tick 2;
3310
	export filter {
3311
		if source = RTS_BGP then {
3312
			ospf_metric1 = 100;
3313
			accept;
3314
		}
3315
		reject;
3316
	};
3317
	area 0.0.0.0 {
3318
		interface "eth*" {
3319
			cost 11;
3320
			hello 15;
3321
			priority 100;
3322
			retransmit 7;
3323
			authentication simple;
3324
			password "aaa";
3325
		};
3326
		interface "ppp*" {
3327
			cost 100;
3328
			authentication cryptographic;
3329
			password "abc" {
3330
				id 1;
3331
				generate to "22-04-2003 11:00:06";
3332
				accept from "17-01-2001 12:01:05";
3333
				algorithm hmac sha384;
3334
			};
3335
			password "def" {
3336
				id 2;
3337
				generate to "22-07-2005 17:03:21";
3338
				accept from "22-02-2001 11:34:06";
3339
				algorithm hmac sha512;
3340
			};
3341
		};
3342
		interface "arc0" {
3343
			cost 10;
3344
			stub yes;
3345
		};
3346
		interface "arc1";
3347
	};
3348
	area 120 {
3349
		stub yes;
3350
		networks {
3351
			172.16.1.0/24;
3352
			172.16.2.0/24 hidden;
3353
		}
3354
		interface "-arc0" , "arc*" {
3355
			type nonbroadcast;
3356
			authentication none;
3357
			strict nonbroadcast yes;
3358
			wait 120;
3359
			poll 40;
3360
			dead count 8;
3361
			neighbors {
3362
				192.168.120.1 eligible;
3363
				192.168.120.2;
3364
				192.168.120.10;
3365
			};
3366
		};
3367
	};
3368
}
3369
</code>
3370

    
3371

    
3372
<sect>Pipe
3373
<label id="pipe">
3374

    
3375
<sect1>Introduction
3376
<label id="pipe-intro">
3377

    
3378
<p>The Pipe protocol serves as a link between two routing tables, allowing
3379
routes to be passed from a table declared as primary (i.e., the one the pipe is
3380
connected to using the <cf/table/ configuration keyword) to the secondary one
3381
(declared using <cf/peer table/) and vice versa, depending on what's allowed by
3382
the filters. Export filters control export of routes from the primary table to
3383
the secondary one, import filters control the opposite direction.
3384

    
3385
<p>The Pipe protocol may work in the transparent mode mode or in the opaque
3386
mode. In the transparent mode, the Pipe protocol retransmits all routes from
3387
one table to the other table, retaining their original source and attributes.
3388
If import and export filters are set to accept, then both tables would have
3389
the same content. The transparent mode is the default mode.
3390

    
3391
<p>In the opaque mode, the Pipe protocol retransmits optimal route from one
3392
table to the other table in a similar way like other protocols send and receive
3393
routes. Retransmitted route will have the source set to the Pipe protocol, which
3394
may limit access to protocol specific route attributes. This mode is mainly for
3395
compatibility, it is not suggested for new configs. The mode can be changed by
3396
<tt/mode/ option.
3397

    
3398
<p>The primary use of multiple routing tables and the Pipe protocol is for
3399
policy routing, where handling of a single packet doesn't depend only on its
3400
destination address, but also on its source address, source interface, protocol
3401
type and other similar parameters. In many systems (Linux being a good example),
3402
the kernel allows to enforce routing policies by defining routing rules which
3403
choose one of several routing tables to be used for a packet according to its
3404
parameters. Setting of these rules is outside the scope of BIRD's work (on
3405
Linux, you can use the <tt/ip/ command), but you can create several routing
3406
tables in BIRD, connect them to the kernel ones, use filters to control which
3407
routes appear in which tables and also you can employ the Pipe protocol for
3408
exporting a selected subset of one table to another one.
3409

    
3410
<sect1>Configuration
3411
<label id="pipe-config">
3412

    
3413
<p><descrip>
3414
	<tag><label id="pipe-peer-table">peer table <m/table/</tag>
3415
	Defines secondary routing table to connect to. The primary one is
3416
	selected by the <cf/table/ keyword.
3417

    
3418
	<tag><label id="pipe-mode">mode opaque|transparent</tag>
3419
	Specifies the mode for the pipe to work in. Default is transparent.
3420
</descrip>
3421

    
3422
<sect1>Attributes
3423
<label id="pipe-attr">
3424

    
3425
<p>The Pipe protocol doesn't define any route attributes.
3426

    
3427
<sect1>Example
3428
<label id="pipe-exam">
3429

    
3430
<p>Let's consider a router which serves as a boundary router of two different
3431
autonomous systems, each of them connected to a subset of interfaces of the
3432
router, having its own exterior connectivity and wishing to use the other AS as
3433
a backup connectivity in case of outage of its own exterior line.
3434

    
3435
<p>Probably the simplest solution to this situation is to use two routing tables
3436
(we'll call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that
3437
packets having arrived from interfaces belonging to the first AS will be routed
3438
according to <cf/as1/ and similarly for the second AS. Thus we have split our
3439
router to two logical routers, each one acting on its own routing table, having
3440
its own routing protocols on its own interfaces. In order to use the other AS's
3441
routes for backup purposes, we can pass the routes between the tables through a
3442
Pipe protocol while decreasing their preferences and correcting their BGP paths
3443
to reflect the AS boundary crossing.
3444

    
3445
<code>
3446
table as1;				# Define the tables
3447
table as2;
3448

    
3449
protocol kernel kern1 {			# Synchronize them with the kernel
3450
	table as1;
3451
	kernel table 1;
3452
}
3453

    
3454
protocol kernel kern2 {
3455
	table as2;
3456
	kernel table 2;
3457
}
3458

    
3459
protocol bgp bgp1 {			# The outside connections
3460
	table as1;
3461
	local as 1;
3462
	neighbor 192.168.0.1 as 1001;
3463
	export all;
3464
	import all;
3465
}
3466

    
3467
protocol bgp bgp2 {
3468
	table as2;
3469
	local as 2;
3470
	neighbor 10.0.0.1 as 1002;
3471
	export all;
3472
	import all;
3473
}
3474

    
3475
protocol pipe {				# The Pipe
3476
	table as1;
3477
	peer table as2;
3478
	export filter {
3479
		if net ~ [ 1.0.0.0/8+] then {	# Only AS1 networks
3480
			if preference>10 then preference = preference-10;
3481
			if source=RTS_BGP then bgp_path.prepend(1);
3482
			accept;
3483
		}
3484
		reject;
3485
	};
3486
	import filter {
3487
		if net ~ [ 2.0.0.0/8+] then {	# Only AS2 networks
3488
			if preference>10 then preference = preference-10;
3489
			if source=RTS_BGP then bgp_path.prepend(2);
3490
			accept;
3491
		}
3492
		reject;
3493
	};
3494
}
3495
</code>
3496

    
3497

    
3498
<sect>RAdv
3499
<label id="radv">
3500

    
3501
<sect1>Introduction
3502
<label id="radv-intro">
3503

    
3504
<p>The RAdv protocol is an implementation of Router Advertisements, which are
3505
used in the IPv6 stateless autoconfiguration. IPv6 routers send (in irregular
3506
time intervals or as an answer to a request) advertisement packets to connected
3507
networks. These packets contain basic information about a local network (e.g. a
3508
list of network prefixes), which allows network hosts to autoconfigure network
3509
addresses and choose a default route. BIRD implements router behavior as defined
3510
in <rfc id="4861"> and also the DNS extensions from <rfc id="6106">.
3511

    
3512
<sect1>Configuration
3513
<label id="radv-config">
3514

    
3515
<p>There are several classes of definitions in RAdv configuration -- interface
3516
definitions, prefix definitions and DNS definitions:
3517

    
3518
<descrip>
3519
	<tag><label id="radv-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
3520
	Interface definitions specify a set of interfaces on which the
3521
	protocol is activated and contain interface specific options.
3522
	See <ref id="proto-iface" name="interface"> common options for
3523
	detailed description.
3524

    
3525
	<tag><label id="radv-prefix">prefix <m/prefix/ { <m/options/ }</tag>
3526
	Prefix definitions allow to modify a list of advertised prefixes. By
3527
	default, the advertised prefixes are the same as the network prefixes
3528
	assigned to the interface. For each network prefix, the matching prefix
3529
	definition is found and its options are used. If no matching prefix
3530
	definition is found, the prefix is used with default options.
3531

    
3532
	Prefix definitions can be either global or interface-specific. The
3533
	second ones are part of interface options. The prefix definition
3534
	matching is done in the first-match style, when interface-specific
3535
	definitions are processed before global definitions. As expected, the
3536
	prefix definition is matching if the network prefix is a subnet of the
3537
	prefix in prefix definition.
3538

    
3539
	<tag><label id="radv-rdnss">rdnss { <m/options/ }</tag>
3540
	RDNSS definitions allow to specify a list of advertised recursive DNS
3541
	servers together with their options. As options are seldom necessary,
3542
	there is also a short variant <cf>rdnss <m/address/</cf> that just
3543
	specifies one DNS server. Multiple definitions are cumulative. RDNSS
3544
	definitions may also be interface-specific when used inside interface
3545
	options. By default, interface uses both global and interface-specific
3546
	options, but that can be changed by <cf/rdnss local/ option.
3547
dsc-iface
3548
	<tag><label id="radv-dnssl">dnssl { <m/options/ }</tag>
3549
	DNSSL definitions allow to specify a list of advertised DNS search
3550
	domains together with their options. Like <cf/rdnss/ above, multiple
3551
	definitions are cumulative, they can be used also as interface-specific
3552
	options and there is a short variant <cf>dnssl <m/domain/</cf> that just
3553
	specifies one DNS search domain.
3554

    
3555
	<tag><label id="radv-trigger">trigger <m/prefix/</tag>
3556
	RAdv protocol could be configured to change its behavior based on
3557
	availability of routes. When this option is used, the protocol waits in
3558
	suppressed state until a <it/trigger route/ (for the specified network)
3559
	is exported to the protocol, the protocol also returnsd to suppressed
3560
	state if the <it/trigger route/ disappears. Note that route export
3561
	depends on specified export filter, as usual. This option could be used,
3562
	e.g., for handling failover in multihoming scenarios.
3563

    
3564
	During suppressed state, router advertisements are generated, but with
3565
	some fields zeroed. Exact behavior depends on which fields are zeroed,
3566
	this can be configured by <cf/sensitive/ option for appropriate
3567
	fields. By default, just <cf/default lifetime/ (also called <cf/router
3568
	lifetime/) is zeroed, which means hosts cannot use the router as a
3569
	default router. <cf/preferred lifetime/ and <cf/valid lifetime/ could
3570
	also be configured as <cf/sensitive/ for a prefix, which would cause
3571
	autoconfigured IPs to be deprecated or even removed.
3572
</descrip>
3573

    
3574
<p>Interface specific options:
3575

    
3576
<descrip>
3577
	<tag><label id="radv-iface-max-ra-interval">max ra interval <m/expr/</tag>
3578
	Unsolicited router advertisements are sent in irregular time intervals.
3579
	This option specifies the maximum length of these intervals, in seconds.
3580
	Valid values are 4-1800. Default: 600
3581

    
3582
	<tag><label id="radv-iface-min-ra-interval">min ra interval <m/expr/</tag>
3583
	This option specifies the minimum length of that intervals, in seconds.
3584
	Must be at least 3 and at most 3/4 * <cf/max ra interval/. Default:
3585
	about 1/3 * <cf/max ra interval/.
3586

    
3587
	<tag><label id="radv-iface-min-delay">min delay <m/expr/</tag>
3588
	The minimum delay between two consecutive router advertisements, in
3589
	seconds. Default: 3
3590

    
3591
	<tag><label id="radv-iface-managed">managed <m/switch/</tag>
3592
	This option specifies whether hosts should use DHCPv6 for IP address
3593
	configuration. Default: no
3594

    
3595
	<tag><label id="radv-iface-other-config">other config <m/switch/</tag>
3596
	This option specifies whether hosts should use DHCPv6 to receive other
3597
	configuration information. Default: no
3598

    
3599
	<tag><label id="radv-iface-link-mtu">link mtu <m/expr/</tag>
3600
	This option specifies which value of MTU should be used by hosts. 0
3601
	means unspecified. Default: 0
3602

    
3603
	<tag><label id="radv-iface-reachable-time">reachable time <m/expr/</tag>
3604
	This option specifies the time (in milliseconds) how long hosts should
3605
	assume a neighbor is reachable (from the last confirmation). Maximum is
3606
	3600000, 0 means unspecified. Default 0.
3607

    
3608
	<tag><label id="radv-iface-retrans-timer">retrans timer <m/expr/</tag>
3609
	This option specifies the time (in milliseconds) how long hosts should
3610
	wait before retransmitting Neighbor Solicitation messages. 0 means
3611
	unspecified. Default 0.
3612

    
3613
	<tag><label id="radv-iface-current-hop-limit">current hop limit <m/expr/</tag>
3614
	This option specifies which value of Hop Limit should be used by
3615
	hosts. Valid values are 0-255, 0 means unspecified. Default: 64
3616

    
3617
	<tag><label id="radv-iface-default-lifetime">default lifetime <m/expr/ [sensitive <m/switch/]</tag>
3618
	This option specifies the time (in seconds) how long (after the receipt
3619
	of RA) hosts may use the router as a default router. 0 means do not use
3620
	as a default router. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3621
	Default: 3 * <cf/max ra	interval/, <cf/sensitive/ yes.
3622

    
3623
	<tag><label id="radv-iface-default-preference-low">default preference low|medium|high</tag>
3624
	This option specifies the Default Router Preference value to advertise
3625
	to hosts. Default: medium.
3626

    
3627
	<tag><label id="radv-iface-rdnss-local">rdnss local <m/switch/</tag>
3628
	Use only local (interface-specific) RDNSS definitions for this
3629
	interface. Otherwise, both global and local definitions are used. Could
3630
	also be used to disable RDNSS for given interface if no local definitons
3631
	are specified. Default: no.
3632

    
3633
	<tag><label id="radv-iface-dnssl-local">dnssl local <m/switch/</tag>
3634
	Use only local DNSSL definitions for this interface. See <cf/rdnss local/
3635
	option above. Default: no.
3636
</descrip>
3637

    
3638

    
3639
<p>Prefix specific options
3640

    
3641
<descrip>
3642
	<tag><label id="radv-prefix-skip">skip <m/switch/</tag>
3643
	This option allows to specify that given prefix should not be
3644
	advertised. This is useful for making exceptions from a default policy
3645
	of advertising all prefixes. Note that for withdrawing an already
3646
	advertised prefix it is more useful to advertise it with zero valid
3647
	lifetime. Default: no
3648

    
3649
	<tag><label id="radv-prefix-onlink">onlink <m/switch/</tag>
3650
	This option specifies whether hosts may use the advertised prefix for
3651
	onlink determination. Default: yes
3652

    
3653
	<tag><label id="radv-prefix-autonomous">autonomous <m/switch/</tag>
3654
	This option specifies whether hosts may use the advertised prefix for
3655
	stateless autoconfiguration. Default: yes
3656

    
3657
	<tag><label id="radv-prefix-valid-lifetime">valid lifetime <m/expr/ [sensitive <m/switch/]</tag>
3658
	This option specifies the time (in seconds) how long (after the
3659
	receipt of RA) the prefix information is valid, i.e., autoconfigured
3660
	IP addresses can be assigned and hosts with that IP addresses are
3661
	considered directly reachable. 0 means the prefix is no longer
3662
	valid. For <cf/sensitive/ option, see <ref id="radv-trigger" name="trigger">.
3663
	Default: 86400 (1 day), <cf/sensitive/ no.
3664

    
3665
	<tag><label id="radv-prefix-preferred-lifetime">preferred lifetime <m/expr/ [sensitive <m/switch/]</tag>
3666
	This option specifies the time (in seconds) how long (after the
3667
	receipt of RA) IP addresses generated from the prefix using stateless
3668
	autoconfiguration remain preferred. For <cf/sensitive/ option,
3669
	see <ref id="radv-trigger" name="trigger">. Default: 14400 (4 hours),
3670
	<cf/sensitive/ no.
3671
</descrip>
3672

    
3673

    
3674
<p>RDNSS specific options:
3675

    
3676
<descrip>
3677
	<tag><label id="radv-rdnss-ns">ns <m/address/</tag>
3678
	This option specifies one recursive DNS server. Can be used multiple
3679
	times for multiple servers. It is mandatory to have at least one
3680
	<cf/ns/ option in <cf/rdnss/ definition.
3681

    
3682
	<tag><label id="radv-rdnss-lifetime">lifetime [mult] <m/expr/</tag>
3683
	This option specifies the time how long the RDNSS information may be
3684
	used by clients after the receipt of RA. It is expressed either in
3685
	seconds or (when <cf/mult/ is used) in multiples of <cf/max ra
3686
	interval/. Note that RDNSS information is also invalidated when
3687
	<cf/default lifetime/ expires. 0 means these addresses are no longer
3688
	valid DNS servers. Default: 3 * <cf/max ra interval/.
3689
</descrip>
3690

    
3691

    
3692
<p>DNSSL specific options:
3693

    
3694
<descrip>
3695
	<tag><label id="radv-dnssl-domain">domain <m/address/</tag>
3696
	This option specifies one DNS search domain. Can be used multiple times
3697
	for multiple domains. It is mandatory to have at least one <cf/domain/
3698
	option in <cf/dnssl/ definition.
3699

    
3700
	<tag><label id="radv-dnssl-lifetime">lifetime [mult] <m/expr/</tag>
3701
	This option specifies the time how long the DNSSL information may be
3702
	used by clients after the receipt of RA. Details are the same as for
3703
	RDNSS <cf/lifetime/ option above. Default: 3 * <cf/max ra interval/.
3704
</descrip>
3705

    
3706

    
3707
<sect1>Example
3708
<label id="radv-exam">
3709

    
3710
<p><code>
3711
protocol radv {
3712
	interface "eth2" {
3713
		max ra interval 5;	# Fast failover with more routers
3714
		managed yes;		# Using DHCPv6 on eth2
3715
		prefix ::/0 {
3716
			autonomous off;	# So do not autoconfigure any IP
3717
		};
3718
	};
3719

    
3720
	interface "eth*";		# No need for any other options
3721

    
3722
	prefix 2001:0DB8:1234::/48 {
3723
		preferred lifetime 0;	# Deprecated address range
3724
	};
3725

    
3726
	prefix 2001:0DB8:2000::/48 {
3727
		autonomous off;		# Do not autoconfigure
3728
	};
3729

    
3730
	rdnss 2001:0DB8:1234::10;	# Short form of RDNSS
3731

    
3732
	rdnss {
3733
		lifetime mult 10;
3734
		ns 2001:0DB8:1234::11;
3735
		ns 2001:0DB8:1234::12;
3736
	};
3737

    
3738
	dnssl {
3739
		lifetime 3600;
3740
		domain "abc.com";
3741
		domain "xyz.com";
3742
	};
3743
}
3744
</code>
3745

    
3746

    
3747
<sect>RIP
3748
<label id="rip">
3749

    
3750
<sect1>Introduction
3751
<label id="rip-intro">
3752

    
3753
<p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol,
3754
where each router broadcasts (to all its neighbors) distances to all networks it
3755
can reach. When a router hears distance to another network, it increments it and
3756
broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some
3757
network goes unreachable, routers keep telling each other that its distance is
3758
the original distance plus 1 (actually, plus interface metric, which is usually
3759
one). After some time, the distance reaches infinity (that's 15 in RIP) and all
3760
routers know that network is unreachable. RIP tries to minimize situations where
3761
counting to infinity is necessary, because it is slow. Due to infinity being 16,
3762
you can't use RIP on networks where maximal distance is higher than 15
3763
hosts.
3764

    
3765
<p>BIRD supports RIPv1 (<rfc id="1058">), RIPv2 (<rfc id="2453">), RIPng (<rfc
3766
id="2080">), and RIP cryptographic authentication (<rfc id="4822">).
3767

    
3768
<p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
3769
convergence, big network load and inability to handle larger networks makes it
3770
pretty much obsolete. It is still usable on very small networks.
3771

    
3772
<sect1>Configuration
3773
<label id="rip-config">
3774

    
3775
<p>RIP configuration consists mainly of common protocol options and interface
3776
definitions, most RIP options are interface specific. RIPng (RIP for IPv6)
3777
protocol instance can be configured by using <cf/rip ng/ instead of just
3778
<cf/rip/ as a protocol type.
3779

    
3780
<code>
3781
protocol rip [ng] [&lt;name&gt;] {
3782
	infinity &lt;number&gt;;
3783
	ecmp &lt;switch&gt; [limit &lt;number&gt;];
3784
	interface &lt;interface pattern&gt; {
3785
		metric &lt;number&gt;;
3786
		mode multicast|broadcast;
3787
		passive &lt;switch&gt;;
3788
		address &lt;ip&gt;;
3789
		port &lt;number&gt;;
3790
		version 1|2;
3791
		split horizon &lt;switch&gt;;
3792
		poison reverse &lt;switch&gt;;
3793
		check zero &lt;switch&gt;;
3794
		update time &lt;number&gt;;
3795
		timeout time &lt;number&gt;;
3796
		garbage time &lt;number&gt;;
3797
		ecmp weight &lt;number&gt;;
3798
		ttl security &lt;switch&gt;; | tx only;
3799
		tx class|dscp &lt;number&gt;;
3800
		tx priority &lt;number&gt;;
3801
		rx buffer &lt;number&gt;;
3802
		tx length &lt;number&gt;;
3803
		check link &lt;switch&gt;;
3804
		authentication none|plaintext|cryptographic;
3805
		password "&lt;text&gt;";
3806
		password "&lt;text&gt;" {
3807
			id &lt;num&gt;;
3808
			generate from "&lt;date&gt;";
3809
			generate to "&lt;date&gt;";
3810
			accept from "&lt;date&gt;";
3811
			accept to "&lt;date&gt;";
3812
			from "&lt;date&gt;";
3813
			to "&lt;date&gt;";
3814
			algorithm ( keyed md5 | keyed sha1 | hmac sha1 | hmac sha256 | hmac sha384 | hmac sha512 );
3815
		};
3816
	};
3817
}
3818
</code>
3819

    
3820
<descrip>
3821
	<tag><label id="rip-infinity">infinity <M>number</M></tag>
3822
	Selects the distance of infinity. Bigger values will make
3823
	protocol convergence even slower. The default value is 16.
3824

    
3825
	<tag><label id="rip-ecmp">ecmp <M>switch</M> [limit <M>number</M>]</tag>
3826
	This option specifies whether RIP is allowed to generate ECMP
3827
	(equal-cost multipath) routes. Such routes are used when there are
3828
	several directions to the destination, each with the same (computed)
3829
	cost. This option also allows to specify a limit on maximum number of
3830
	nexthops in one route. By default, ECMP is disabled. If enabled,
3831
	default	value of the limit is 16.
3832

    
3833
	<tag><label id="rip-iface">interface <m/pattern/ [, <m/.../] { <m/options/ }</tag>
3834
	Interface definitions specify a set of interfaces on which the
3835
	protocol is activated and contain interface specific options.
3836
	See <ref id="proto-iface" name="interface"> common options for
3837
	detailed description.
3838
</descrip>
3839

    
3840
<p>Interface specific options:
3841

    
3842
<descrip>
3843
	<tag><label id="rip-iface-metric">metric <m/num/</tag>
3844
	This option specifies the metric of the interface. When a route is
3845
	received from the interface, its metric is increased by this value
3846
	before further processing. Valid values are 1-255, but values higher
3847
	than infinity has no further meaning. Default: 1.
3848

    
3849
	<tag><label id="rip-iface-mode">mode multicast|broadcast</tag>
3850
	This option selects the mode for RIP to use on the interface. The
3851
	default is multicast mode for RIPv2 and broadcast mode for RIPv1.
3852
	RIPng always uses the multicast mode.
3853

    
3854
	<tag><label id="rip-iface-passive">passive <m/switch/</tag>
3855
	Passive interfaces receive routing updates but do not transmit any
3856
	messages. Default: no.
3857

    
3858
	<tag><label id="rip-iface-address">address <m/ip/</tag>
3859
	This option specifies a destination address used for multicast or
3860
	broadcast messages, the default is the official RIP (224.0.0.9) or RIPng
3861
	(ff02::9) multicast address, or an appropriate broadcast address in the
3862
	broadcast mode.
3863

    
3864
	<tag><label id="rip-iface-port">port <m/number/</tag>
3865
	This option selects an UDP port to operate on, the default is the
3866
	official RIP (520) or RIPng (521) port.
3867

    
3868
	<tag><label id="rip-iface-version">version 1|2</tag>
3869
	This option selects the version of RIP used on the interface. For RIPv1,
3870
	automatic subnet aggregation is not implemented, only classful network
3871
	routes and host routes are propagated. Note that BIRD allows RIPv1 to be
3872
	configured with features that are defined for RIPv2 only, like
3873
	authentication or using multicast sockets. The default is RIPv2 for IPv4
3874
	RIP, the option is not supported for RIPng, as no further versions are
3875
	defined.
3876

    
3877
	<tag><label id="rip-iface-version-only">version only <m/switch/</tag>
3878
	Regardless of RIP version configured for the interface, BIRD accepts
3879
	incoming packets of any RIP version. This option restrict accepted
3880
	packets to the configured version. Default: no.
3881

    
3882
	<tag><label id="rip-iface-split-horizon">split horizon <m/switch/</tag>
3883
	Split horizon is a scheme for preventing routing loops. When split
3884
	horizon is active, routes are not regularly propagated back to the
3885
	interface from which they were received. They are either not propagated
3886
	back at all (plain split horizon) or propagated back with an infinity
3887
	metric (split horizon with poisoned reverse). Therefore, other routers
3888
	on the interface will not consider the router as a part of an
3889
	independent path to the destination of the route. Default: yes.
3890

    
3891
	<tag><label id="rip-iface-poison-reverse">poison reverse <m/switch/</tag>
3892
	When split horizon is active, this option specifies whether the poisoned
3893
	reverse variant (propagating routes back with an infinity metric) is
3894
	used. The poisoned reverse has some advantages in faster convergence,
3895
	but uses more network traffic. Default: yes.
3896

    
3897
	<tag><label id="rip-iface-check-zero">check zero <m/switch/</tag>
3898
	Received RIPv1 packets with non-zero values in reserved fields should
3899
	be discarded. This option specifies whether the check is performed or
3900
	such packets are just processed as usual. Default: yes.
3901

    
3902
	<tag><label id="rip-iface-update-time">update time <m/number/</tag>
3903
	Specifies the number of seconds between periodic updates. A lower number
3904
	will mean faster convergence but bigger network load. Default: 30.
3905

    
3906
	<tag><label id="rip-iface-timeout-time">timeout time <m/number/</tag>
3907
	Specifies the time interval (in seconds) between the last received route
3908
	announcement and the route expiration. After that, the network is
3909
	considered unreachable, but still is propagated with infinity distance.
3910
	Default: 180.
3911

    
3912
	<tag><label id="rip-iface-garbage-time">garbage time <m/number/</tag>
3913
	Specifies the time interval (in seconds) between the route expiration
3914
	and the removal of the unreachable network entry. The garbage interval,
3915
	when a route with infinity metric is propagated, is used for both
3916
	internal (after expiration) and external (after withdrawal) routes.
3917
	Default: 120.
3918

    
3919
	<tag><label id="rip-iface-ecmp-weight">ecmp weight <m/number/</tag>
3920
	When ECMP (multipath) routes are allowed, this value specifies a
3921
	relative weight used for nexthops going through the iface. Valid
3922
	values are 1-256. Default value is 1.
3923

    
3924
	<tag><label id="rip-iface-auth">authentication none|plaintext|cryptographic</tag>
3925
	Selects authentication method to be used. <cf/none/ means that packets
3926
	are not authenticated at all, <cf/plaintext/ means that a plaintext
3927
	password is embedded into each packet, and <cf/cryptographic/ means that
3928
	packets are authenticated using some cryptographic hash function
3929
	selected by option <cf/algorithm/ for each key. The default
3930
	cryptographic algorithm for RIP keys is Keyed-MD5. If you set
3931
	authentication to not-none, it is a good idea to add <cf>password</cf>
3932
	section. Default: none.
3933

    
3934
	<tag><label id="rip-iface-pass">password "<m/text/"</tag>
3935
	Specifies a password used for authentication. See <ref id="proto-pass"
3936
	name="password"> common option for detailed description.
3937

    
3938
	<tag><label id="rip-iface-ttl-security">ttl security [<m/switch/ | tx only]</tag>
3939
	TTL security is a feature that protects routing protocols from remote
3940
	spoofed packets by using TTL 255 instead of TTL 1 for protocol packets
3941
	destined to neighbors. Because TTL is decremented when packets are
3942
	forwarded, it is non-trivial to spoof packets with TTL 255 from remote
3943
	locations.
3944

    
3945
	If this option is enabled, the router will send RIP packets with TTL 255
3946
	and drop received packets with TTL less than 255. If this option si set
3947
	to <cf/tx only/, TTL 255 is used for sent packets, but is not checked
3948
	for received packets. Such setting does not offer protection, but offers
3949
	compatibility with neighbors regardless of whether they use ttl
3950
	security.
3951

    
3952
	For RIPng, TTL security is a standard behavior (required by <rfc
3953
	id="2080">) and therefore default value is yes. For IPv4 RIP, default
3954
	value is no.
3955

    
3956
	<tag><label id="rip-iface-tx-class">tx class|dscp|priority <m/number/</tag>
3957
	These options specify the ToS/DiffServ/Traffic class/Priority of the
3958
	outgoing RIP packets. See <ref id="proto-tx-class" name="tx class"> common
3959
	option for detailed description.
3960

    
3961
	<tag><label id="rip-iface-rx-buffer">rx buffer <m/number/</tag>
3962
	This option specifies the size of buffers used for packet processing.
3963
	The buffer size should be bigger than maximal size of received packets.
3964
	The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
3965

    
3966
	<tag><label id="rip-iface-tx-length">tx length <m/number/</tag>
3967
	This option specifies the maximum length of generated RIP packets. To
3968
	avoid IP fragmentation, it should not exceed the interface MTU value.
3969
	The default value is 532 for IPv4 RIP and interface MTU value for RIPng.
3970

    
3971
	<tag><label id="rip-iface-check-link">check link <m/switch/</tag>
3972
	If set, the hardware link state (as reported by OS) is taken into
3973
	consideration. When the link disappears (e.g. an ethernet cable is
3974
	unplugged), neighbors are immediately considered unreachable and all
3975
	routes received from them are withdrawn. It is possible that some
3976
	hardware drivers or platforms do not implement this feature.
3977
	Default: no.
3978
</descrip>
3979

    
3980
<sect1>Attributes
3981
<label id="rip-attr">
3982

    
3983
<p>RIP defines two route attributes:
3984

    
3985
<descrip>
3986
	<tag>int <cf/rip_metric/</tag>
3987
	RIP metric of the route (ranging from 0 to <cf/infinity/). When routes
3988
	from different RIP instances are available and all of them have the same
3989
	preference, BIRD prefers the route with lowest <cf/rip_metric/. When a
3990
	non-RIP route is exported to RIP, the default metric is 1.
3991

    
3992
	<tag><label id="rta-rip-tag">int rip_tag/</tag>
3993
	RIP route tag: a 16-bit number which can be used to carry additional
3994
	information with the route (for example, an originating AS number in
3995
	case of external routes). When a non-RIP route is exported to RIP, the
3996
	default tag is 0.
3997
</descrip>
3998

    
3999
<sect1>Example
4000
<label id="rip-exam">
4001

    
4002
<p><code>
4003
protocol rip {
4004
        debug all;
4005
        port 1520;
4006
        period 12;
4007
        garbage time 60;
4008
        interface "eth0" { metric 3; mode multicast; };
4009
        interface "eth*" { metric 2; mode broadcast; };
4010
        authentication cryptographic;
4011
        password "secret-shared-key" { algorithm hmac sha256; };
4012
        import filter { print "importing"; accept; };
4013
        export filter { print "exporting"; accept; };
4014
}
4015
</code>
4016

    
4017
<sect>RPKI
4018

    
4019
<sect1>Introduction
4020

    
4021
<p>The Resource Public Key Infrastructure (RPKI) is mechanism for origin
4022
validation of BGP routes (RFC 6480). BIRD supports only so-called RPKI-based
4023
origin validation. There is implemented RPKI to Router (RPKI-RTR) protocol (RFC
4024
6810).  It uses some of the RPKI data to allow a router to verify that the
4025
autonomous system announcing an IP address prefix is in fact authorized to do
4026
so. This is not crypto checked so can be violated. But it should prevent the
4027
vast majority of accidental hijackings on the Internet today, e.g. the famous
4028
Pakastani accidental announcement of YouTube's address space.
4029

    
4030
<p>The RPKI-RTR protocol receives and maintains a set of ROAs from a cache
4031
server (also called validator). You can validate routes (RFC 6483) using
4032
function <cf/roa_check()/ in filter and set it as import filter at the BGP
4033
protocol. BIRD should re-validate all of affected routes after RPKI update by
4034
RFC 6811, but we don't support it yet! You can use a BIRD's client command
4035
<cf>reload in <m/bgp_protocol_name/</cf> for manual call of revalidation of all
4036
routes.
4037

    
4038
<sect1>Supported transports
4039
<itemize>
4040
        <item>Unprotected transport over TCP uses a port 323. The cache server
4041
        and BIRD router should be on the same trusted and controlled network
4042
        for security reasons.
4043
        <item>SSHv2 encrypted transport connection uses the normal SSH port
4044
        22.
4045
</itemize>
4046

    
4047
<sect1>Configuration
4048

    
4049
<p>We currently support just one cache server per protocol. However you can
4050
define more RPKI protocols generally.
4051

    
4052
<code>
4053
protocol rpki [&lt;name&gt;] {
4054
        roa4 { table &lt;tab&gt;; };
4055
        roa6 { table &lt;tab&gt;; };
4056
        remote &lt;ip&gt; | "&lt;domain&gt;" [port &lt;num&gt;];
4057
        port &lt;num&gt;;
4058
        refresh [keep] &lt;num&gt;;
4059
        retry [keep] &lt;num&gt;;
4060
        expire [keep] &lt;num&gt;;
4061
        transport tcp;
4062
        transport ssh {
4063
                bird private key "&lt;/path/to/id_rsa&gt;";
4064
                remote public key "&lt;/path/to/known_host&gt;";
4065
                user "&lt;name&gt;";
4066
        };
4067
}
4068
</code>
4069

    
4070
<p>Alse note that you have to specify ROA table into which will be imported
4071
routes from a cache server. If you want to import only IPv4 prefixes you have
4072
to specify only roa4 table. Similarly with IPv6 prefixes only. If you want to
4073
fetch both IPv4 and even IPv6 ROAs you have to specify both types of ROA
4074
tables.
4075

    
4076
<sect2>RPKI protocol options
4077

    
4078
<descrip>
4079
        <tag>remote <m/ip/ | "<m/hostname/" [port <m/num/]</tag> Specifies
4080
        a destination address of the cache server.  Can be specified by an IP
4081
        address or by full domain name string.  Only one cache can be specified
4082
        per protocol. This option is required.
4083

    
4084
        <tag>port <m/num/</tag> Specifies the port number. The default port
4085
        number is 323 for transport without any encryption and 22 for transport
4086
        with SSH encryption.
4087

    
4088
        <tag>refresh [keep] <m/num/</tag> Time period in seconds. Tells how
4089
        long to wait before next attempting to poll the cache using a Serial
4090
        Query or a Reset Query packet. Must be lower than 86400 seconds (one
4091
        day). Too low value can caused a false positive detection of
4092
        network connection problems.  A keyword <cf/keep/ suppresses updating
4093
        this value by a cache server.
4094
        Default: 3600 seconds
4095

    
4096
        <tag>retry [keep] <m/num/</tag> Time period in seconds between a failed
4097
        Serial/Reset Query and a next attempt.  Maximum allowed value is 7200
4098
        seconds (two hours). Too low value can caused a false positive
4099
        detection of network connection problems.  A keyword <cf/keep/
4100
        suppresses updating this value by a cache server.
4101
        Default: 600 seconds
4102

    
4103
        <tag>expire [keep] <m/num/</tag> Time period in seconds. Received
4104
        records are deleted if the client was unable to successfully refresh
4105
        data for this time period.  Must be in range from 600 seconds (ten
4106
        minutes) to 172800 seconds (two days).  A keyword <cf/keep/
4107
        suppresses updating this value by a cache server.
4108
        Default: 7200 seconds
4109

    
4110
        <tag>transport tcp</tag> Unprotected transport over TCP. It's a default
4111
        transport. Should be used only on secure private networks.
4112
        Default: tcp
4113

    
4114
        <tag>transport ssh { <m/SSH transport options.../ }</tag> It enables a
4115
        SSHv2 transport encryption. Cannot be combined with a TCP transport.
4116
        Default: off
4117
</descrip>
4118

    
4119
<sect3>SSH transport options
4120
<descrip>
4121
	<tag>bird private key "<m>/path/to/id_rsa</m>"</tag>
4122
	A path to the BIRD's private SSH key for authentication.
4123
	It can be a <cf><m>id_rsa</m></cf> file.
4124

    
4125
	<tag>remote public key "<m>/path/to/known_host</m>"</tag>
4126
	A path to the cache's public SSH key for verification identity
4127
	of the cache server. It could be a path to <cf><m>known_host</m></cf> file.
4128

    
4129
	<tag>user "<m/name/"</tag>
4130
	A SSH user name for authentication. This option is a required.
4131
</descrip>
4132

    
4133
<sect1>Examples
4134
<sect2>BGP origin validation
4135
<p>Policy: Don't import <cf/ROA_INVALID/ routes.
4136
<code>
4137
roa4 table r4;
4138
roa6 table r6;
4139

    
4140
protocol rpki {
4141
	debug all;
4142
	
4143
	roa4 { table r4; };
4144
	roa6 { table r6; };
4145

    
4146
	# Please, do not use rpki-validator.realmv6.org in production
4147
	remote "rpki-validator.realmv6.org" port 8282;
4148
	
4149
	retry keep 5;
4150
	refresh keep 30;
4151
	expire 600;
4152
}
4153

    
4154
filter peer_in {
4155
	if (roa_check(r4, net, bgp_path.last) = ROA_INVALID ||
4156
	    roa_check(r6, net, bgp_path.last) = ROA_INVALID) then
4157
	{
4158
		print "Ignore invalid ROA ", net, " for ASN ", bgp_path.last;
4159
		reject;
4160
	}
4161
	accept;
4162
}
4163

    
4164
protocol bgp {
4165
	debug all;
4166
	local as 65000;
4167
	neighbor 192.168.2.1 as 65001;
4168
	import filter peer_in;
4169
}
4170
</code>
4171

    
4172
<sect2>SSHv2 transport encryption
4173
<code>
4174
roa4 table r4;
4175
roa6 table r6;
4176

    
4177
protocol rpki {
4178
	debug all;
4179
	
4180
	roa4 { table r4; };
4181
	roa6 { table r6; };
4182
	
4183
	remote 127.0.0.1 port 2345;
4184
	transport ssh {
4185
		bird private key "/home/birdgeek/.ssh/id_rsa";
4186
		remote public key "/home/birdgeek/.ssh/known_hosts";
4187
		user "birdgeek";
4188
	};
4189
	
4190
	# Default interval values
4191
}
4192
</code>
4193

    
4194

    
4195

    
4196
<sect>Static
4197
<label id="static">
4198

    
4199
<p>The Static protocol doesn't communicate with other routers in the network,
4200
but instead it allows you to define routes manually. This is often used for
4201
specifying how to forward packets to parts of the network which don't use
4202
dynamic routing at all and also for defining sink routes (i.e., those telling to
4203
return packets as undeliverable if they are in your IP block, you don't have any
4204
specific destination for them and you don't want to send them out through the
4205
default route to prevent routing loops).
4206

    
4207
<p>There are four types of static routes: `classical' routes telling to forward
4208
packets to a neighboring router (single path or multipath, possibly weighted),
4209
device routes specifying forwarding to hosts on a directly connected network,
4210
recursive routes computing their nexthops by doing route table lookups for a
4211
given IP, and special routes (sink, blackhole etc.)  which specify a special
4212
action to be done instead of forwarding the packet.
4213

    
4214
<p>When the particular destination is not available (the interface is down or
4215
the next hop of the route is not a neighbor at the moment), Static just
4216
uninstalls the route from the table it is connected to and adds it again as soon
4217
as the destination becomes adjacent again.
4218

    
4219
<p>There are three classes of definitions in Static protocol configuration --
4220
global options, static route definitions, and per-route options. Usually, the
4221
definition of the protocol contains mainly a list of static routes.
4222

    
4223
<p>Global options:
4224

    
4225
<descrip>
4226
	<tag><label id="static-check-link">check link <m/switch/</tag>
4227
	If set, hardware link states of network interfaces are taken into
4228
	consideration.  When link disappears (e.g. ethernet cable is unplugged),
4229
	static routes directing to that interface are removed. It is possible
4230
	that some hardware drivers or platforms do not implement this feature.
4231
	Default: off.
4232

    
4233
	<tag><label id="static-igp-table">igp table <m/name/</tag>
4234
	Specifies a table that is used for route table lookups of recursive
4235
	routes. Default: the same table as the protocol is connected to.
4236
</descrip>
4237

    
4238
<p>Route definitions (each may also contain a block of per-route options):
4239

    
4240
<descrip>
4241
	<tag><label id="static-route-via-ip">route <m/prefix/ via <m/ip/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]]</tag>
4242
	Static single path route through a neighboring router. For link-local next hops,
4243
	interface can be specified as a part of the address (e.g.,
4244
	<cf/via fe80::1234%eth0/). MPLS labels should be specified in outer-first order.
4245

    
4246
	<tag><label id="static-route-via-mpath">route <m/prefix/ via <m/ip/ [mpls <m/num/[/<m/num/[/<m/num/[...]]]] [weight <m/num/] [bfd <m/switch/] [via ...]</tag>
4247
	Static multipath route. Contains several nexthops (gateways), possibly
4248
	with their weights and MPLS labels.
4249

    
4250
	<tag><label id="static-route-via-iface">route <m/prefix/ via <m/"interface"/</tag>
4251
	Static device route through an interface to hosts on a directly
4252
	connected network.
4253

    
4254
	<tag><label id="static-route-recursive">route <m/prefix/ recursive <m/ip/</tag>
4255
	Static recursive route, its nexthop depends on a route table lookup for
4256
	given IP address.
4257

    
4258
	<tag><label id="static-route-drop">route <m/prefix/ blackhole|unreachable|prohibit</tag>
4259
	Special routes specifying to silently drop the packet, return it as
4260
	unreachable or return it as administratively prohibited. First two
4261
	targets are also known as <cf/drop/ and <cf/reject/.
4262
</descrip>
4263

    
4264
<p>Per-route options:
4265

    
4266
<descrip>
4267
	<tag><label id="static-route-bfd">bfd <m/switch/</tag>
4268
	The Static protocol could use BFD protocol for next hop liveness
4269
	detection. If enabled, a BFD session to the route next hop is created
4270
	and the static route is BFD-controlled -- the static route is announced
4271
	only if the next hop liveness is confirmed by BFD. If the BFD session
4272
	fails, the static route is removed. Note that this is a bit different
4273
	compared to other protocols, which may use BFD as an advisory mechanism
4274
	for fast failure detection but ignores it if a BFD session is not even
4275
	established.
4276

    
4277
	This option can be used for static routes with a direct next hop, or
4278
	also for for individual next hops in a static multipath route (see
4279
	above). Note that BFD protocol also has to be configured, see
4280
	<ref id="bfd" name="BFD"> section for details. Default value is no.
4281

    
4282
	<tag><label id="static-route-filter"><m/filter expression/</tag>
4283
	This is a special option that allows filter expressions to be configured
4284
	on per-route basis. Can be used multiple times. These expressions are
4285
	evaluated when the route is originated, similarly to the import filter
4286
	of the static protocol. This is especially useful for configuring route
4287
	attributes, e.g., <cf/ospf_metric1 = 100;/ for a route that will be
4288
	exported to the OSPF protocol.
4289
</descrip>
4290

    
4291
<p>Static routes have no specific attributes.
4292

    
4293
<p>Example static config might look like this:
4294

    
4295
<p><code>
4296
protocol static {
4297
	table testable;			# Connect to a non-default routing table
4298
	check link;			# Advertise routes only if link is up
4299
	route 0.0.0.0/0 via 198.51.100.130; # Default route
4300
	route 10.0.0.0/8 multipath	# Multipath route
4301
		via 198.51.100.10 weight 2
4302
		via 198.51.100.20 bfd	# BFD-controlled next hop
4303
		via 192.0.2.1;
4304
	route 203.0.113.0/24 unreachable; # Sink route
4305
	route 10.2.0.0/24 via "arc0";	# Secondary network
4306
	route 192.168.10.0/24 via 198.51.100.100 {
4307
		ospf_metric1 = 20;	# Set extended attribute
4308
	}
4309
	route 192.168.10.0/24 via 198.51.100.100 {
4310
		ospf_metric2 = 100;	# Set extended attribute
4311
		ospf_tag = 2;		# Set extended attribute
4312
		bfd;			# BFD-controlled route
4313
	}
4314
}
4315
</code>
4316

    
4317

    
4318
<chapt>Conclusions
4319
<label id="conclusion">
4320

    
4321
<sect>Future work
4322
<label id="future-work">
4323

    
4324
<p>Although BIRD supports all the commonly used routing protocols, there are
4325
still some features which would surely deserve to be implemented in future
4326
versions of BIRD:
4327

    
4328
<itemize>
4329
<item>Opaque LSA's
4330
<item>Route aggregation and flap dampening
4331
<item>Multipath routes
4332
<item>Multicast routing protocols
4333
<item>Ports to other systems
4334
</itemize>
4335

    
4336

    
4337
<sect>Getting more help
4338
<label id="help">
4339

    
4340
<p>If you use BIRD, you're welcome to join the bird-users mailing list
4341
(<HTMLURL URL="mailto:bird-users@network.cz" name="bird-users@network.cz">)
4342
where you can share your experiences with the other users and consult
4343
your problems with the authors. To subscribe to the list, visit
4344
<HTMLURL URL="http://bird.network.cz/?m_list" name="http://bird.network.cz/?m_list">.
4345
The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
4346

    
4347
<p>BIRD is a relatively young system and it probably contains some bugs. You can
4348
report any problems to the bird-users list and the authors will be glad to solve
4349
them, but before you do so, please make sure you have read the available
4350
documentation and that you are running the latest version (available at
4351
<HTMLURL URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">).
4352
(Of course, a patch which fixes the bug is always welcome as an attachment.)
4353

    
4354
<p>If you want to understand what is going inside, Internet standards are a good
4355
and interesting reading. You can get them from
4356
<HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or a
4357
nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc"
4358
name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
4359

    
4360
<p><it/Good luck!/
4361

    
4362
</book>
4363

    
4364
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4365
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