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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,
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ASCII text and dvi/postscript (generated from sgml using
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sgmltools). You should always edit master copy.
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This is a slightly modified linuxdoc dtd.  Anything in <descrip> tags is considered definition of
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configuration primitives, <cf> is fragment of configuration within normal text, <m> is
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"meta" information within fragment of configuration - something in config which is not keyword.
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    (set-fill-column 100)
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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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<sect>What is BIRD
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<p><label id="intro">
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The name `BIRD' is actually an acronym standing for `BIRD Internet Routing Daemon'.
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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 standing
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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 discover in a moment)
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which works as a dynamic router in an Internet type network (that is, in a network running either
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the IPv4 or the IPv6 protocol). Routers are devices which forward packets between interconnected
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networks in 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 Internet to discover
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the topology of the network which allows them to find optimal (in terms of some metric) rules for
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forwarding of packets (which are called routing tables) and to adapt themselves to the
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changing conditions such 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 hard to configure and
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not open to any changes (on the other hand, their special hardware design allows them to keep up with lots of high-speed network interfaces, better than general-purpose computer does). Fortunately, most operating systems of the UNIX family allow an ordinary 
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computer to act as a router and forward packets belonging to the other hosts, but only according to
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a statically configured table.
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<p>A <em/Routing Daemon/ is in UNIX terminology a non-interactive program running on
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background which does the dynamic part of Internet routing, that is it communicates
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with the other routers, calculates routing tables and sends them to the OS kernel
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which does the actual packet forwarding. There already exist other such routing
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daemons: routed (RIP only), GateD (non-free), Zebra<HTMLURL URL="http://www.zebra.org">
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and MRTD<HTMLURL URL="http://sourceforge.net/projects/mrt">, but their capabilities are
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limited and they are relatively hard to configure 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 be
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used in near future and to have a clean extensible architecture allowing new routing
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protocols to be incorporated easily. Among other features, BIRD 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 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
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		to change the configuration, just edit the configuration file
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		and notify BIRD to re-read it and it will smoothly switch itself
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		to the new configuration, not disturbing routing protocols
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		unless 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 University, Prague,
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Czech Republic as a student project. It can be freely distributed under the terms of the GNU General
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Public License.
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<p>BIRD has been designed to work on all UNIX-like systems. It has
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been developed and tested under Linux 2.0 to 2.6, and then ported to
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FreeBSD, NetBSD and OpenBSD, porting to other systems (even non-UNIX
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ones) should be relatively easy due to its highly modular
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architecture.
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<p>BIRD supports either IPv4 or IPv6 protocol, but have to be compiled
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separately for each one. Therefore, a dualstack router would run two
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instances of BIRD (one for IPv4 and one for IPv6), with completely
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separate setups (configuration files, tools ...).
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<sect>Installing BIRD
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<p>On a recent UNIX system with GNU development tools (GCC, binutils, m4, make) 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:
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<tt/--enable-ipv6/ which enables building of an IPv6 version of BIRD,
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<tt/--with-protocols=/ to produce a slightly smaller 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.
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<file>/usr/local</file>.
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<sect>Running BIRD
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<p>You can pass several command-line options to bird:
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<descrip>
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	<tag>-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>-d</tag>
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	enable debug messages and run bird in foreground.
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	<tag>-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>-p</tag>
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	just parse the config file and exit. Return value is zero if the config file is valid,
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	nonzero if there are some errors.
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	<tag>-s <m/name of communication socket/</tag>
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	use given filename for a  socket for communications with the client, default is <it/prefix/<file>/var/run/bird.ctl</file>.
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	<tag>-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>-g <m/group/</tag>
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	use that group ID, see the next section for details.
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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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<p>BIRD, as a routing daemon, uses several privileged operations (like
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setting routing table and using raw sockets). Traditionally, BIRD is
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executed and runs with root privileges, which may be prone to security
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problems. The recommended way is to use a privilege restriction
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(options <cf/-u/, <cf/-g/). In that case BIRD is executed with root
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privileges, but it changes its user and group ID to an unprivileged
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ones, while using Linux capabilities to retain just required
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privileges (capabilities CAP_NET_*). Note that the control socket is
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created before the privileges are dropped, but the config file is read
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after that. The privilege restriction is not implemented in BSD port
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of BIRD.
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<p>A nonprivileged user (as an argument to <cf/-u/ options) may be the
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user <cf/nobody/, but it is suggested to use a new dedicated user
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account (like <cf/bird/). The similar considerations apply for
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the group option, but there is one more condition -- the users
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in the same group can use <file/birdc/ to control BIRD.
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<p>Finally, there is a possibility to use external tools to run BIRD in
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an environment with restricted privileges. This may need some
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configuration, but it is generally easy -- BIRD needs just the
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standard library, privileges to read the config file and create the
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control socket and the CAP_NET_* capabilities.
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<chapt>About routing tables
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<p>BIRD has one or more routing tables which may or may not be
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synchronized with OS kernel and which may or may not be synchronized with
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each other (see the Pipe protocol). Each routing table contains a list of
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known routes. Each route consists of:
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<itemize>
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	<item>network prefix this route is for (network address and prefix length -- the number of bits forming the network part of the 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
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	using this 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
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	may not be present (typically protocol metrics)
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</itemize>
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Routing table maintains multiple entries
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for a network, but at most one entry for one network and one
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protocol. The entry with the highest preference is used for routing (we
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will call such an entry the <it/selected route/). If
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there are more entries with the same preference and they are from the same
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protocol, the protocol decides (typically according to metrics). If they aren't,
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an internal ordering is used to break the tie. You can
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get the list of route attributes in the Route attributes section.
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<p>Each protocol is connected to a routing table through two filters
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which can accept, reject and modify the routes. An <it/export/
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filter checks routes passed from the routing table to the protocol,
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an <it/import/ filter checks routes in the opposite direction.
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When the routing table gets a route from a protocol, it recalculates
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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
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in the network. Note that although most protocols are interested 
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in receiving just selected routes, some protocols (e.g. the <cf/Pipe/
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protocol) receive and process all entries in routing tables (accepted
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by filters).
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<p><label id="dsc-sorted">Usually, a routing table just chooses a
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selected route from a list of entries for one network. But if the
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<cf/sorted/ option is activated, these lists of entries are kept
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completely sorted (according to preference or some protocol-dependent
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metric).
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This is needed for some features of some protocols
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(e.g. <cf/secondary/ option of BGP protocol, which allows to accept
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not just a selected route, but the first route (in the sorted list)
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that is accepted by filters), but it is incompatible with some other
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features (e.g. <cf/deterministic med/ option of BGP protocol, which
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activates a way of choosing selected route that cannot be described
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using comparison and ordering). Minor advantage is that routes are
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shown sorted in <cf/show route/, minor disadvantage is that it is
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slightly more computationally expensive.
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<chapt>Configuration
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<sect>Introduction
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<p>BIRD is configured using a text configuration file. Upon startup, BIRD reads <it/prefix/<file>/etc/bird.conf</file> (unless the
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<tt/-c/ command line option is given). Configuration may be changed at user's request: if you modify
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the 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
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which allows you to talk with BIRD in an extensive way.
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<p>In the config, everything on a line after <cf/#/ or inside <cf>/*
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*/</cf> is a comment, whitespace characters are treated as a single space. If there's a variable number of options, they are grouped using
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the <cf/{ }/ brackets. Each option is terminated by a <cf/;/. Configuration
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is case sensitive.
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<p>Here is an example of a simple config file. It enables
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synchronization of routing tables with OS kernel, scans for 
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new network interfaces every 10 seconds 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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<p><descrip>
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	<tag>include "<m/filename/"</tag> 
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	This statement causes inclusion of a new file. The maximal depth is set to 5.
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	<tag>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 <cf/{
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	error, trace }/ etc.) into selected destination (a file specified as a filename string,
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	syslog with optional name argument, or the stderr 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. You may specify more than one <cf/log/ line to establish logging to multiple
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	destinations. Default: log everything to the system log.
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	<tag>debug protocols all|off|{ states, routes, filters, interfaces, events, packets }</tag>
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	Set global defaults of protocol debugging options. See <cf/debug/ in the following section. Default: off.
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	<tag>debug commands <m/number/</tag>
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	Control logging of client connections (0 for no logging, 1 for
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	logging of connects and disconnects, 2 and higher for logging of
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	all client commands). Default: 0.
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	<tag>mrtdump "<m/filename/"</tag>
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	Set MRTdump file name. This option must be specified to allow MRTdump feature.
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	Default: no dump file.
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	<tag>mrtdump protocols all|off|{ states, messages }</tag>
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	Set global defaults of MRTdump options. See <cf/mrtdump/ in the following section.
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	Default: off.
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	<tag>filter <m/name local variables/{ <m/commands/ }</tag> Define a filter. You can learn more about filters
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	in the following chapter. 
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	<tag>function <m/name/ (<m/parameters/) <m/local variables/ { <m/commands/ }</tag> Define a function. You can learn more
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	about functions in the following chapter.
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	<tag>protocol rip|ospf|bgp|... [<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 "rip5" generated
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	automatically if you don't specify any <cf><m/name/</cf>). You can learn more about
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	configuring protocols in their own chapters. When <cf>from <m/name2/</cf> expression is
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	used, initial protocol options are taken from protocol or template <cf><m/name2/</cf>
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	You can run more than one instance of most protocols (like RIP or BGP). By default, no
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	instances are configured.
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	<tag>template rip|bgp|... [<m/name/ [from <m/name2/]] { <m>protocol options</m> }</tag>
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	Define a protocol template instance called <cf><m/name/</cf> (or with a name like "bgp1"
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	generated automatically if you don't specify any <cf><m/name/</cf>). Protocol templates can
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	be used to group common options when many similarly configured protocol instances are to be
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	defined. Protocol 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 <cf/from/ expression)
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	are not implemented for OSPF protocol.
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	<tag>define <m/constant/ = (<m/expression/)|<m/number/|<m/IP address/</tag>
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	Define a constant. You can use it later in every place you could use a simple integer or an IP address.
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	Besides, there are some predefined numeric constants based on /etc/iproute2/rt_* files.
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	A list of defined constants can be seen (together with other symbols) using 'show symbols' command.
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	<tag>router id <m/IPv4 address/</tag> Set BIRD's router ID. It's a world-wide unique identification of your router, usually one of router's IPv4 addresses. Default: in IPv4 version, the lowest IP address of a non-loopback interface. In IPv6 version, this option is mandatory. 
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	<tag>listen bgp [address <m/address/] [port <m/port/] [dual]</tag>
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	This option allows to specify address and port where BGP
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	protocol should listen. It is global option as listening
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	socket is common to all BGP instances. Default is to listen on
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	all addresses (0.0.0.0) and port 179. In IPv6 mode, option
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	<cf/dual/ can be used to specify that BGP socket should accept
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	both IPv4 and IPv6 connections (but even in that case, BIRD
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	would accept IPv6 routes only). Such behavior was default in
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	older versions of BIRD.
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	<tag>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
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	BIRD.  The first argument specifies for which purpose such
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	format is used. <cf/route/ is a format used in 'show route'
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	command output, <cf/protocol/ is used in 'show protocols'
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	command output, <cf/base/ is used for other commands and
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	<cf/log/ is used in a log file.
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	"<m/format1/" is a format string using <it/strftime(3)/
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	notation (see <it/man strftime/ for details). <m/limit> and
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	"<m/format2/" allow to specify the second format string for
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	times in past deeper than <m/limit/ seconds. There are two
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	shorthands: <cf/iso long/ is a ISO 8601 date/time format
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	(YYYY-MM-DD hh:mm:ss) that can be also specified using <cf/"%F
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	%T"/. <cf/iso short/ is a variant of ISO 8601 that uses just
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	the time format (hh:mm:ss) for near times (up to 20 hours in
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	the past) and the date format (YYYY-MM-DD) for far times. This
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	is a shorthand for <cf/"%T" 72000 "%F"/.
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	By default, BIRD uses an short, ad-hoc format for <cf/route/
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	and <cf/protocol/ times, and a <cf/iso long/ similar format
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	(DD-MM-YYYY hh:mm:ss) for <cf/base/ and <cf/log/. These
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	defaults are here for a compatibility with older versions
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	and might change in the future.
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	<tag>table <m/name/ [sorted]</tag>
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	Create a new routing table. The default routing table is
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	created implicitly, other routing tables have to be added by
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	this command. Option <cf/sorted/ can be used to enable
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	sorting of routes, see <ref id="dsc-sorted" name="sorted table">
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	description for details.
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	<tag>roa table <m/name/ [ { roa table options ... } ]</tag>
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	Create a new ROA (Route Origin Authorization) table. ROA
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	tables can be used to validate route origination of BGP
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	routes. A ROA table contains ROA entries, each consist of a
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	network prefix, a max prefix length and an AS number. A ROA
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	entry specifies prefixes which could be originated by that AS
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	number. ROA tables could be filled with data from RPKI (RFC
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	6480) or from public databases like Whois. ROA tables are 
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	examined by <cf/roa_check()/ operator in filters.
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	Currently, there is just one option,
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	<cf>roa <m/prefix/ max <m/num/ as <m/num/</cf>, which
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	can be used to populate the ROA table with static ROA
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	entries. The option may be used multiple times. Other entries
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	can be added dynamically by <cf/add roa/ command.
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	<tag>eval <m/expr/</tag> Evaluates given filter expression. It
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	is used by us for testing of filters.
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</descrip>
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<sect>Protocol options
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<p>For each protocol instance, you can configure a bunch of options.
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Some of them (those described in this section) are generic, some are
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specific to the protocol (see sections talking about the protocols).
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<p>Several options use a <cf><m/switch/</cf> argument. It can be either
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<cf/on/, <cf/yes/ or a numeric expression with a non-zero value for the
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option to be enabled or <cf/off/, <cf/no/ or a numeric expression evaluating
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to zero to disable it. An empty <cf><m/switch/</cf> is equivalent to <cf/on/
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("silence means agreement").
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<descrip>
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	<tag>preference <m/expr/</tag> Sets the preference of routes generated by this protocol. Default: protocol dependent.
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	<tag>disabled <m/switch/</tag> Disables the protocol. You can change the disable/enable status from the command
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	line interface without needing to touch the configuration. Disabled protocols are not activated. Default: protocol is enabled.
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	<tag>debug all|off|{ states, routes, filters, interfaces, events, packets }</tag>
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	Set protocol debugging options. If asked, each protocol is capable of
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	writing trace messages about its work to the log (with category
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	<cf/trace/). You can either request printing of <cf/all/ trace messages
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	or only of the types selected: <cf/states/ for protocol state changes
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	(protocol going up, down, starting, stopping etc.),
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	<cf/routes/ for routes exchanged with the routing table,
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	<cf/filters/ for details on route filtering,
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	<cf/interfaces/ for interface change events sent to the protocol,
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	<cf/events/ for events internal to the protocol and
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	<cf/packets/ for packets sent and received by the protocol. Default: off.
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	<tag>mrtdump all|off|{ states, messages }</tag>
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	Set protocol MRTdump flags. MRTdump is a standard binary
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	format for logging information from routing protocols and
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	daemons.  These flags control what kind of information is
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	logged from the protocol to the MRTdump file (which must be
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	specified by global <cf/mrtdump/ option, see the previous
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	section). Although these flags are similar to flags of
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	<cf/debug/ option, their meaning is different and
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	protocol-specific. For BGP protocol, <cf/states/ logs BGP
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	state changes and <cf/messages/ logs received BGP messages.
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	Other protocols does not support MRTdump yet.
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	<tag>router id <m/IPv4 address/</tag> This option can be used
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	to override global router id for a given protocol. Default:
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	uses global router id.
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	<tag>import all | none | filter <m/name/ | filter { <m/filter commands/ } | where <m/filter expression/</tag> 
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	Specify a filter to be used for filtering routes coming from
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	the protocol to the routing table. <cf/all/ is shorthand for
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	<cf/where true/ and <cf/none/ is shorthand for
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	<cf/where false/. Default: <cf/all/.
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	<tag>export <m/filter/</tag>
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	This is similar to the <cf>import</cf> keyword, except that it
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	works in the direction from the routing table to the protocol.
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	Default: <cf/none/.
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	<tag>import limit <m/number/ [action warn | block | restart | disable]</tag>
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	Specify an import route limit (a maximum number of routes
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	imported from the protocol) and optionally the action to be
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	taken when the limit is hit. Warn action just prints warning
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	log message. Block action ignores new routes coming from the
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	protocol. Restart and disable actions shut the protocol down
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	like appropriate commands. Disable is the default action if an
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	action is not explicitly specified. Note that limits are reset
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	during protocol reconfigure, reload or restart.
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	Default: <cf/none/.
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	<tag>export limit <m/number/ [action warn | block | restart | disable]</tag>
474
	Specify an export route limit, works similarly to
475
	the <cf>import limit</cf> option, but for the routes exported
476
	to the protocol. This option is experimental, there are some
477
	problems in details of its behavior -- the number of exported
478
	routes can temporarily exceed the limit without triggering it
479
	during protocol reload, exported routes counter ignores route
480
	blocking and block action also blocks route updates of already
481
	accepted routes -- and these details will probably change in
482
	the future. Default: <cf/none/.
483

    
484
	<tag>description "<m/text/"</tag> This is an optional
485
	description of the protocol. It is displayed as a part of the
486
	output of 'show route all' command.
487

    
488
	<tag>table <m/name/</tag> Connect this protocol to a non-default routing table.
489
</descrip>
490

    
491
<p>There are several options that give sense only with certain protocols:
492

    
493
<descrip>
494
	<tag><label id="dsc-iface">interface [-] [ "<m/mask/" ] [ <m/prefix/ ] [, ...] [ { <m/option/ ; [...] } ]</tag>
495

    
496
	Specifies a set of interfaces on which the protocol is activated with
497
	given interface-specific options. A set of interfaces specified by one
498
	interface option is described using an interface pattern. The
499
	interface pattern consists of a sequence of clauses (separated by
500
	commas), each clause may contain a mask, a prefix, or both of them. An
501
	interface matches the clause if its name matches the mask (if
502
	specified) and its address matches the prefix (if specified). Mask is
503
	specified as shell-like pattern. For IPv6, the prefix part of a clause
504
	is generally ignored and interfaces are matched just by their name.
505

    
506
	An interface matches the pattern if it matches any of its
507
	clauses. If the clause begins with <cf/-/, matching interfaces are
508
	excluded. Patterns are parsed left-to-right, thus
509
	<cf/interface "eth0", -"eth*", "*";/ means eth0 and all
510
	non-ethernets.
511

    
512
	An interface option can be used more times with different
513
	interfaces-specific options, in that case for given interface
514
	the first matching interface option is used.
515
	
516
	This option is allowed in Direct, OSPF, RIP and RAdv protocols,
517
	but in OSPF protocol it is used in <cf/area/ subsection.
518

    
519
	Default: none.
520

    
521
	Examples:
522

    
523
	<cf>interface "*" { type broadcast; };</cf> - start the protocol on all interfaces with
524
	<cf>type broadcast</cf> option.
525

    
526
	<cf>interface "eth1", "eth4", "eth5" { type ptp; };</cf> - start the protocol
527
	on enumerated interfaces with <cf>type ptp</cf> option.
528
	
529
	<cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol on all
530
	interfaces that have address from 192.168.0.0/16, but not
531
	from 192.168.1.0/24.
532

    
533
	<cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol on all
534
	interfaces that have address from 192.168.0.0/16, but not
535
	from 192.168.1.0/24.
536

    
537
	<cf>interface "eth*" 192.168.1.0/24;</cf> - start the protocol on all
538
	ethernet interfaces that have address from 192.168.1.0/24.
539

    
540
	<tag><label id="dsc-pass">password "<m/password/" [ { id <m/num/; generate from <m/time/; generate to <m/time/; accept from <m/time/; accept to <m/time/; } ]</tag>
541
	Specifies a password that can be used by the protocol. Password option can
542
	be used more times to specify more passwords. If more passwords are
543
	specified, it is a protocol-dependent decision which one is really
544
	used. Specifying passwords does not mean that authentication is
545
	enabled, authentication can be enabled by separate, protocol-dependent
546
	<cf/authentication/ option.
547
	
548
	This option is allowed in OSPF and RIP protocols. BGP has also
549
	<cf/password/ option, but it is slightly different and described
550
	separately.
551

    
552
	Default: none.
553
</descrip>
554

    
555
<p>Password option can contain section with some (not necessary all) password sub-options:
556

    
557
<descrip>
558
	<tag>id <M>num</M></tag>
559
	 ID of the password, (0-255). If it's not used, BIRD will choose
560
	 ID based on an order of the password item in the interface. For
561
	 example, second password item in one interface will have default
562
	 ID 2. ID is used by some routing protocols to identify which
563
	 password was used to authenticate protocol packets.
564

    
565
	<tag>generate from "<m/time/"</tag>
566
	 The start time of the usage of the password for packet signing.
567
	 The format of <cf><m/time/</cf> is <tt>dd-mm-yyyy HH:MM:SS</tt>.
568

    
569
	<tag>generate to "<m/time/"</tag>
570
	 The last time of the usage of the password for packet signing.
571

    
572
	<tag>accept from "<m/time/"</tag>
573
	 The start time of the usage of the password for packet verification.
574

    
575
	<tag>accept to "<m/time/"</tag>
576
	 The last time of the usage of the password for packet verification.
577
</descrip>
578

    
579
<chapt>Remote control
580

    
581
<p>You can use the command-line client <file>birdc</file> to talk with
582
a running BIRD. Communication is done using a <file/bird.ctl/ UNIX
583
domain socket (unless changed with the <tt/-s/ option given to both
584
the server and the client). The commands can perform simple actions
585
such as enabling/disabling of protocols, telling BIRD to show various
586
information, telling it to show routing table filtered by filter, or
587
asking BIRD to reconfigure. Press <tt/?/ at any time to get online
588
help. Option <tt/-r/ can be used to enable a restricted mode of BIRD
589
client, which allows just read-only commands (<cf/show .../). Option
590
<tt/-v/ can be passed to the client, to make it dump numeric return
591
codes along with the messages. You do not necessarily need to use
592
<file/birdc/ to talk to BIRD, your own applications could do that, too
593
-- the format of communication between BIRD and <file/birdc/ is stable
594
(see the programmer's documentation).
595

    
596
Many commands have the <m/name/ of the protocol instance as an argument.
597
This argument can be omitted if there exists only a single instance.
598

    
599
<p>Here is a brief list of supported functions:
600

    
601
<descrip>
602
	<tag>dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
603
	Dump contents of internal data structures to the debugging output.
604

    
605
	<tag>show status</tag>
606
	Show router status, that is BIRD version, uptime and time from last reconfiguration.
607

    
608
	<tag>show protocols [all]</tag>
609
	Show list of protocol instances along with tables they are connected to and protocol status, possibly giving verbose information, if <cf/all/ is specified.
610

    
611
	<tag>show ospf interface [<m/name/] ["<m/interface/"]</tag>
612
	Show detailed information about OSPF interfaces.
613

    
614
	<tag>show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
615
	Show a list of OSPF neighbors and a state of adjacency to them.
616

    
617
	<tag>show ospf state [all] [<m/name/]</tag>
618
	Show detailed information about OSPF areas based on a content
619
	of the link-state database. It shows network topology, stub
620
	networks, aggregated networks and routers from other areas and
621
	external routes. The command shows information about reachable
622
	network nodes, use option <cf/all/ to show information about
623
	all network nodes in the link-state database.
624

    
625
	<tag>show ospf topology [all] [<m/name/]</tag>
626
	Show a topology of OSPF areas based on a content of the
627
	link-state database.  It is just a stripped-down version of
628
	'show ospf state'.
629

    
630
	<tag>show ospf lsadb [global | area <m/id/ | link] [type <m/num/] [lsid <m/id/] [self | router <m/id/] [<m/name/] </tag>
631
	Show contents of an OSPF LSA database. Options could be used to filter entries.
632

    
633
	<tag>show static [<m/name/]</tag>
634
	Show detailed information about static routes.
635

    
636
	<tag>show interfaces [summary]</tag>
637
	Show the list of interfaces. For each interface, print its type, state, MTU and addresses assigned. 
638

    
639
	<tag>show symbols [table|filter|function|protocol|template|roa|<m/symbol/]</tag>
640
	Show the list of symbols defined in the configuration (names of protocols, routing tables etc.).
641

    
642
	<tag>show route [[for] <m/prefix/|<m/IP/] [table <m/sym/] [filter <m/f/|where <m/c/] [(export|preexport) <m/p/] [protocol <m/p/] [<m/options/]</tag>
643
	Show contents of a routing table (by default of the main one),
644
	that is routes, their metrics and (in case the <cf/all/ switch is given)
645
	all their attributes.
646

    
647
	<p>You can specify a <m/prefix/ if you want to print routes for a
648
	specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
649
	the entry which will be used for forwarding of packets to the given
650
	destination. By default, all routes for each network are printed with
651
	the selected one at the top, unless <cf/primary/ is given in which case
652
	only the selected route is shown.
653

    
654
	<p>You can also ask for printing only routes processed and accepted by
655
	a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
656
	</cf> or matching a given condition (<cf>where <m/condition/</cf>).
657
	The <cf/export/ and <cf/preexport/ switches ask for printing of entries
658
	that are exported to the specified protocol. With <cf/preexport/, the
659
	export filter of the protocol is skipped.
660

    
661
	<p>You can also select just routes added by a specific protocol.
662
	<cf>protocol <m/p/</cf>.
663

    
664
	<p>The <cf/stats/ switch requests showing of route statistics (the
665
	number of networks, number of routes before and after filtering). If
666
	you use <cf/count/ instead, only the statistics will be printed.
667

    
668
	<tag>show roa [<m/prefix/ | in <m/prefix/ | for <m/prefix/] [as <m/num/] [table <m/t/>]</tag>
669
	Show contents of a ROA table (by default of the first one).
670
	You can specify a <m/prefix/ to print ROA entries for a
671
	specific network. If you use <cf>for <m/prefix/</cf>, you'll
672
	get all entries relevant for route validation of the network
673
	prefix; i.e., ROA entries whose prefixes cover the network
674
	prefix. Or you can use <cf>in <m/prefix/</cf> to get ROA entries
675
	covered by the network prefix. You could also use <cf/as/ option
676
	to show just entries for given AS.
677

    
678
	<tag>add roa <m/prefix/ max <m/num/] as <m/num/ [table <m/t/>]</tag>
679
	Add a new ROA entry to a ROA table. Such entry is called
680
	<it/dynamic/ compared to <it/static/ entries specified in the
681
	config file. These dynamic entries survive reconfiguration.
682

    
683
	<tag>delete roa <m/prefix/ max <m/num/] as <m/num/ [table <m/t/>]</tag>
684
	Delete the specified ROA entry from a ROA table. Only dynamic
685
	ROA entries (i.e., the ones added by <cf/add roa/ command) can
686
	be deleted.
687

    
688
	<tag>flush roa [table <m/t/>]</tag>
689
	Remove all dynamic ROA entries from a ROA table.
690

    
691
	<tag>configure [soft] ["<m/config file/"]</tag>
692
	Reload configuration from a given file. BIRD will smoothly
693
	switch itself to the new configuration, protocols are
694
	reconfigured if possible, restarted otherwise. Changes in
695
	filters usually lead to restart of affected protocols. If
696
	<cf/soft/ option is used, changes in filters does not cause
697
	BIRD to restart affected protocols, therefore already accepted
698
	routes (according to old filters) would be still propagated,
699
	but new routes would be processed according to the new
700
	filters.
701

    
702
	<tag>enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
703
	Enable, disable or restart a given protocol instance, instances matching the <cf><m/pattern/</cf> or <cf/all/ instances.
704

    
705
	<tag>reload [in|out] <m/name/|"<m/pattern/"|all</tag>
706
	
707
	Reload a given protocol instance, that means re-import routes
708
	from the protocol instance and re-export preferred routes to
709
	the instance. If <cf/in/ or <cf/out/ options are used, the
710
	command is restricted to one direction (re-import or
711
	re-export).
712

    
713
	This command is useful if appropriate filters have changed but
714
	the protocol instance was not restarted (or reloaded),
715
	therefore it still propagates the old set of routes. For example
716
	when <cf/configure soft/ command was used to change filters.
717

    
718
	Re-export always succeeds, but re-import is protocol-dependent
719
	and might fail (for example, if BGP neighbor does not support
720
	route-refresh extension). In that case, re-export is also
721
	skipped. Note that for the pipe protocol, both directions are
722
	always reloaded together (<cf/in/ or <cf/out/ options are
723
	ignored in that case).
724

    
725
	<tag/down/
726
	Shut BIRD down.
727

    
728
	<tag>debug <m/protocol/|<m/pattern/|all all|off|{ states | routes | filters | events | packets }</tag>
729
	Control protocol debugging.
730
</descrip>
731

    
732
<chapt>Filters
733

    
734
<sect>Introduction
735

    
736
<p>BIRD contains a simple programming language. (No, it can't yet read mail :-). There are
737
two objects in this language: filters and functions. Filters are interpreted by BIRD core when a route is
738
being passed between protocols and routing tables. The filter language contains control structures such
739
as if's and switches, but it allows no loops. An example of a filter using many features can be found in <file>filter/test.conf</file>. 
740

    
741
<p>Filter gets the route, looks at its attributes and
742
modifies some of them if it wishes. At the end, it decides whether to
743
pass the changed route through (using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks
744
like this:
745

    
746
<code>
747
filter not_too_far
748
int var;
749
{
750
	if defined( rip_metric ) then
751
		var = rip_metric;
752
	else {
753
		var = 1;
754
		rip_metric = 1;
755
	}
756
	if rip_metric &gt; 10 then
757
		reject "RIP metric is too big";
758
	else
759
		accept "ok";
760
}
761
</code>
762

    
763
<p>As you can see, a filter has a header, a list of local variables, and a body. The header consists of
764
the <cf/filter/ keyword followed by a (unique) name of filter. The list of local variables consists of
765
<cf><M>type name</M>;</cf> pairs where each pair defines one local variable. The body consists of
766
<cf> { <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You can group
767
several statements to a single compound statement by using braces (<cf>{ <M>statements</M> }</cf>) which is useful if
768
you want to make a bigger block of code conditional.
769

    
770
<p>BIRD supports functions, so that you don't have to repeat the same blocks of code over and
771
over. Functions can have zero or more parameters and they can have local variables. Recursion is not allowed. Function definitions
772
look like this:
773

    
774
<code>
775
function name ()
776
int local_variable;
777
{
778
	local_variable = 5;
779
}
780

    
781
function with_parameters (int parameter)
782
{
783
	print parameter;
784
}
785
</code>
786

    
787
<p>Unlike in C, variables are declared after the <cf/function/ line, but before the first <cf/{/. You can't declare
788
variables in nested blocks. Functions are called like in C: <cf>name();
789
with_parameters(5);</cf>. Function may return values using the <cf>return <m/[expr]/</cf>
790
command. Returning a value exits from current function (this is similar to C).
791

    
792
<p>Filters are declared in a way similar to functions except they can't have explicit
793
parameters. They get a route table entry as an implicit parameter, it is also passed automatically 
794
to any functions called. The filter must terminate with either
795
<cf/accept/ or <cf/reject/ statement. If there's a runtime error in filter, the route
796
is rejected. 
797

    
798
<p>A nice trick to debug filters is to use <cf>show route filter
799
<m/name/</cf> from the command line client. An example session might look
800
like:
801

    
802
<code>
803
pavel@bug:~/bird$ ./birdc -s bird.ctl
804
BIRD 0.0.0 ready.
805
bird> show route
806
10.0.0.0/8         dev eth0 [direct1 23:21] (240)
807
195.113.30.2/32    dev tunl1 [direct1 23:21] (240)
808
127.0.0.0/8        dev lo [direct1 23:21] (240)
809
bird> show route ?
810
show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
811
bird> show route filter { if 127.0.0.5 &tilde; net then accept; }
812
127.0.0.0/8        dev lo [direct1 23:21] (240)
813
bird>
814
</code>
815

    
816
<sect>Data types
817

    
818
<p>Each variable and each value has certain type. Booleans, integers and enums are
819
incompatible with each other (that is to prevent you from shooting in the foot).
820

    
821
<descrip>
822
	<tag/bool/ This is a boolean type, it can have only two values, <cf/true/ and
823
	  <cf/false/. Boolean is the only type you can use in <cf/if/
824
	  statements.
825

    
826
	<tag/int/ This is a general integer type, you can expect it to store signed values from -2000000000
827
	  to +2000000000. Overflows are not checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
828

    
829
	<tag/pair/ This is a pair of two short integers. Each component can have values from 0 to
830
	  65535. Literals of this type are written as <cf/(1234,5678)/. The same syntax can also be
831
	  used to construct a pair from two arbitrary integer expressions (for example <cf/(1+2,a)/).
832

    
833
	<tag/quad/ This is a dotted quad of numbers used to represent
834
	  router IDs (and others).  Each component can have a value
835
	  from 0 to 255. Literals of this type are written like IPv4
836
	  addresses.
837

    
838
	<tag/string/ This is a string of characters. There are no ways to modify strings in
839
	  filters. You can pass them between functions, assign them to variables of type <cf/string/, print
840
	  such variables, but you can't concatenate two strings. String literals
841
	  are written as <cf/"This is a string constant"/.
842

    
843
	<tag/ip/ This type can hold a single IP address. Depending on the compile-time configuration of BIRD you are using, it
844
	  is either an IPv4 or IPv6 address. IP addresses are written in the standard notation (<cf/10.20.30.40/ or <cf/fec0:3:4::1/). You can apply special operator <cf>.mask(<M>num</M>)</cf>
845
	  on values of type ip. It masks out all but first <cf><M>num</M></cf> bits from the IP
846
	  address. So <cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
847

    
848
	<tag/prefix/ This type can hold a network prefix consisting of IP address and prefix length. Prefix literals are written as
849
	  <cf><M>ipaddress</M>/<M>pxlen</M></cf>, or
850
	  <cf><m>ipaddress</m>/<m>netmask</m></cf>. There are two special
851
	  operators on prefixes:
852
	  <cf/.ip/ which extracts the IP address from the pair, and <cf/.len/, which separates prefix
853
	  length from the pair. So <cf>1.2.0.0/16.pxlen = 16</cf> is true.
854

    
855
	<tag/ec/ This is a specialized type used to represent BGP
856
	  extended community values. It is essentially a 64bit value,
857
	  literals of this type are usually written as <cf>(<m/kind/,
858
	  <m/key/, <m/value/)</cf>, where <cf/kind/ is a kind of
859
	  extended community (e.g. <cf/rt/ / <cf/ro/ for a route
860
	  target / route origin communities), the format and possible
861
	  values of <cf/key/ and <cf/value/ are usually integers, but
862
	  it depends on the used kind. Similarly to pairs, ECs can be
863
	  constructed using expressions for <cf/key/ and
864
	  <cf/value/ parts, (e.g. <cf/(ro, myas, 3*10)/, where
865
	  <cf/myas/ is an integer variable).
866
 
867
	<tag/int|pair|quad|ip|prefix|ec|enum set/
868
	  Filters recognize four types of sets. Sets are similar to strings: you can pass them around
869
	  but you can't modify them. Literals of type <cf>int set</cf> look like <cf>
870
	  [ 1, 2, 5..7 ]</cf>. As you can see, both simple values and ranges are permitted in
871
	  sets.
872

    
873
	  For pair sets, expressions like <cf/(123,*)/ can be used to denote ranges (in
874
	  that case <cf/(123,0)..(123,65535)/). You can also use <cf/(123,5..100)/ for range
875
	  <cf/(123,5)..(123,100)/. You can also use <cf/*/ and <cf/a..b/ expressions
876
	  in the first part of a pair, note that such expressions are translated to a set
877
	  of intervals, which may be memory intensive. E.g. <cf/(*,4..20)/ is translated to
878
	  <cf/(0,4..20), (1,4..20), (2,4..20), ... (65535, 4..20)/.
879

    
880
	  EC sets use similar expressions like pair sets, e.g. <cf/(rt, 123, 10..20)/ 
881
	  or <cf/(ro, 123, *)/. Expressions requiring the translation (like  <cf/(rt, *, 3)/)
882
	  are not allowed (as they usually have 4B range for ASNs).
883

    
884
	  You can also use expressions for int, pair and EC set values. However it must
885
	  be possible to evaluate these expressions before daemon boots. So you can use
886
	  only constants inside them. E.g.
887
	<code>
888
	 define one=1;
889
	 define myas=64500;
890
	 int set odds;
891
	 pair set ps;
892
	 ec set es;
893

    
894
	 odds = [ one, 2+1, 6-one, 2*2*2-1, 9, 11 ];
895
	 ps = [ (1,one+one), (3,4)..(4,8), (5,*), (6,3..6), (7..9,*) ];
896
	 es = [ (rt, myas, 3*10), (rt, myas+one, 0..16*16*16-1), (ro, myas+2, *) ];
897
	</code>
898

    
899
	  Sets of prefixes are special: their literals does not allow ranges, but allows
900
	  prefix patterns that are written as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
901
	  Prefix <cf><m>ip1</m>/<m>len1</m></cf> matches prefix pattern <cf><m>ip2</m>/<m>len2</m>{<m>l</m>,<m>h</m>}</cf> if 
902
	  the first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are identical and <cf>len1 &lt;= ip1 &lt;= len2</cf>.
903
	  A valid prefix pattern has to satisfy <cf>low &lt;= high</cf>, but <cf/pxlen/ is not constrained by <cf/low/
904
	  or <cf/high/. Obviously, a prefix matches a prefix set literal if it matches any prefix pattern in the
905
	  prefix set literal.
906

    
907
	  There are also two shorthands for prefix patterns: <cf><m>address</m>/<m/len/+</cf> is a shorthand for
908
	  <cf><m>address</m>/<m/len/{<m/len/,<m/maxlen/}</cf> (where <cf><m>maxlen</m></cf> is 32 for IPv4 and 128 for IPv6), 
909
	  that means network prefix <cf><m>address</m>/<m/len/</cf> and all its subnets. <cf><m>address</m>/<m/len/-</cf>
910
	  is a shorthand for <cf><m>address</m>/<m/len/{0,<m/len/}</cf>, that means network prefix <cf><m>address</m>/<m/len/</cf>
911
	  and all its supernets (network prefixes that contain it).
912

    
913
	  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} ]</cf> matches
914
	  prefix <cf>1.0.0.0/8</cf>, all subprefixes of <cf>2.0.0.0/8</cf>, all superprefixes of <cf>3.0.0.0/8</cf> and prefixes
915
	  <cf/4.X.X.X/ whose prefix length is 16 to 24. <cf>[ 0.0.0.0/0{20,24} ]</cf> matches all prefixes (regardless of
916
	  IP address) whose prefix length is 20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP address
917
	  <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 &tilde; [ 1.0.0.0/8{15,17} ]</cf> is true,
918
	  but <cf>1.0.0.0/16 &tilde; [ 1.0.0.0/8- ]</cf> is false.
919

    
920
	  Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
921
	  in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as 
922
	  <cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
923
	  <cf>192.168.0.0/16{24,32}</cf>.
924

    
925
	<tag/enum/
926
	  Enumeration types are fixed sets of possibilities. You can't define your own
927
	  variables of such type, but some route attributes are of enumeration
928
	  type. Enumeration types are incompatible with each other.
929

    
930
	<tag/bgppath/
931
	  BGP path is a list of autonomous system numbers. You can't write literals of this type.
932
	  There are several special operators on bgppaths:
933

    
934
	  <cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
935

    
936
          <cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
937

    
938
	  Both <cf/first/ and <cf/last/ return zero if there is no appropriate ASN,
939
          for example if the path contains an AS set element as the first (or the last) part.
940

    
941
          <cf><m/P/.len</cf> returns the length of path <m/P/.
942

    
943
          <cf>prepend(<m/P/,<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and returns the result.
944
          Statement <cf><m/P/ = prepend(<m/P/, <m/A/);</cf> can be shortened to
945
          <cf><m/P/.prepend(<m/A/);</cf> if <m/P/ is appropriate route attribute
946
          (for example <cf/bgp_path/).
947

    
948
	<tag/bgpmask/
949
	  BGP masks are patterns used for BGP path matching
950
	  (using <cf>path &tilde; [= 2 3 5 * =]</cf> syntax). The masks
951
	  resemble wildcard patterns as used by UNIX shells. Autonomous
952
	  system numbers match themselves, <cf/*/ matches any (even empty)
953
	  sequence of arbitrary AS numbers and <cf/?/ matches one arbitrary AS number.
954
	  For example, if <cf>bgp_path</cf> is 4 3 2 1, then:
955
	  <tt>bgp_path &tilde; [= * 4 3 * =]</tt> is true, but 
956
	  <tt>bgp_path &tilde; [= * 4 5 * =]</tt> is false.
957
	  BGP mask expressions can also contain integer expressions enclosed in parenthesis
958
	  and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>.
959
	  There is also old syntax that uses / .. / instead of [= .. =] and ? instead of *.
960

    
961
	<tag/clist/
962
	  Clist is similar to a set, except that unlike other sets, it
963
	  can be modified. The type is used for community list (a set
964
	  of pairs) and for cluster list (a set of quads). There exist
965
	  no literals of this type. There are three special operators on
966
	  clists:
967

    
968
          <cf>add(<m/C/,<m/P/)</cf> adds pair (or quad) <m/P/ to clist
969
	  <m/C/ and returns the result.  If item <m/P/ is already in
970
	  clist <m/C/, it does nothing. <m/P/ may also be a clist,
971
	  in that case all its members are added; i.e., it works as clist union.
972

    
973
          <cf>delete(<m/C/,<m/P/)</cf> deletes pair (or quad)
974
	  <m/P/ from clist <m/C/ and returns the result.  If clist
975
	  <m/C/ does not contain item <m/P/, it does nothing.
976
	  <m/P/ may also be a pair (or quad) set, in that case the
977
	  operator deletes all items from clist <m/C/ that are also
978
	  members of set <m/P/. Moreover, <m/P/ may also be a clist,
979
	  which works analogously; i.e., it works as clist difference.
980

    
981
          <cf>filter(<m/C/,<m/P/)</cf> deletes all items from clist
982
	  <m/C/ that are not members of pair (or quad) set <m/P/.
983
	  I.e., <cf/filter/ do the same as <cf/delete/ with inverted
984
	  set <m/P/. <m/P/ may also be a clist, which works analogously;
985
	  i.e., it works as clist intersection.
986

    
987
          Statement <cf><m/C/ = add(<m/C/, <m/P/);</cf> can be shortened to
988
          <cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route
989
          attribute (for example <cf/bgp_community/). Similarly for
990
          <cf/delete/ and <cf/filter/.
991

    
992
	<tag/eclist/
993
	  Eclist is a data type used for BGP extended community lists.
994
	  Eclists are very similar to clists, but they are sets of ECs
995
	  instead of pairs. The same operations (like <cf/add/,
996
	  <cf/delete/, or <cf/&tilde;/ membership operator) can be
997
	  used to modify or test eclists, with ECs instead of pairs as
998
	  arguments.
999
</descrip>
1000

    
1001
<sect>Operators
1002

    
1003
<p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>, parentheses <cf/(a*(b+c))/, comparison
1004
<cf/(a=b, a!=b, a&lt;b, a&gt;=b)/. Logical operations include unary not (<cf/!/), and (<cf/&amp;&amp;/) and or (<cf/&verbar;&verbar;/). 
1005
Special operators include <cf/&tilde;/ for "is element of a set" operation - it can be
1006
used on element and set of elements of the same type (returning true if element is contained in the given set), or
1007
on two strings (returning true if first string matches a shell-like pattern stored in second string) or on IP and prefix (returning true if IP is within the range defined by that prefix), or on
1008
prefix and prefix (returning true if first prefix is more specific than second one) or on bgppath and bgpmask (returning true if the path matches the mask) or on number and bgppath (returning true if the number is in the path) or on pair/quad and clist (returning true if the pair/quad is element of the clist) or on clist and pair/quad set (returning true if there is an element of the clist that is also a member of the pair/quad set).
1009

    
1010
<p>There is one operator related to ROA infrastructure -
1011
<cf/roa_check()/. It examines a ROA table and does RFC 6483 route
1012
origin validation for a given network prefix. The basic usage
1013
is <cf>roa_check(<m/table/)</cf>, which checks current route (which
1014
should be from BGP to have AS_PATH argument) in the specified ROA
1015
table and returns ROA_UNKNOWN if there is no relevant ROA, ROA_VALID
1016
if there is a matching ROA, or ROA_INVALID if there are some relevant
1017
ROAs but none of them match. There is also an extended variant
1018
<cf>roa_check(<m/table/, <m/prefix/, <m/asn/)</cf>, which allows to
1019
specify a prefix and an ASN as arguments.
1020

    
1021

    
1022
<sect>Control structures
1023

    
1024
<p>Filters support two control structures: conditions and case switches. 
1025

    
1026
<p>Syntax of a condition is: <cf>if
1027
<M>boolean expression</M> then <M>command1</M>; else <M>command2</M>;</cf> and you can use <cf>{
1028
<M>command_1</M>; <M>command_2</M>; <M>...</M> }</cf> instead of either command. The <cf>else</cf>
1029
clause may be omitted. If the <cf><m>boolean expression</m></cf> is true, <cf><m>command1</m></cf> is executed, otherwise <cf><m>command2</m></cf> is executed.
1030

    
1031
<p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case <m/expr/ { else: |
1032
<m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [ ... ] }</cf>. The expression after
1033
<cf>case</cf> can be of any type which can be on the left side of the &tilde; operator and anything that could
1034
be a member of a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/ grouping.
1035
If <cf><m/expr/</cf> matches one of the <cf/:/ clauses, statements between it and next <cf/:/ statement are executed. If <cf><m/expr/</cf> matches neither of the <cf/:/ clauses, the statements after <cf/else:/ are executed.
1036

    
1037
<p>Here is example that uses <cf/if/ and <cf/case/ structures:
1038

    
1039
<code>
1040
case arg1 {
1041
	2: print "two"; print "I can do more commands without {}";
1042
	3 .. 5: print "three to five";
1043
	else: print "something else";
1044
}
1045

    
1046
if 1234 = i then printn "."; else { 
1047
  print "not 1234"; 
1048
  print "You need {} around multiple commands"; 
1049
}
1050
</code>
1051

    
1052
<sect>Route attributes
1053

    
1054
<p>A filter is implicitly passed a route, and it can access its
1055
attributes just like it accesses variables. Attempts to access undefined
1056
attribute result in a runtime error; you can check if an attribute is
1057
defined by using the <cf>defined( <m>attribute</m> )</cf> operator.
1058
One notable exception to this rule are attributes of clist type, where
1059
undefined value is regarded as empty clist for most purposes.
1060

    
1061
<descrip>
1062
	<tag><m/prefix/ net</tag>
1063
	Network the route is talking about. Read-only. (See the chapter about routing tables.)
1064

    
1065
	<tag><m/enum/ scope</tag>
1066
	The scope of the route. Possible values: <cf/SCOPE_HOST/ for
1067
	routes local to this host, <cf/SCOPE_LINK/ for those specific
1068
	for a physical link, <cf/SCOPE_SITE/ and
1069
	<cf/SCOPE_ORGANIZATION/ for private routes and
1070
	<cf/SCOPE_UNIVERSE/ for globally visible routes. This
1071
	attribute is not interpreted by BIRD and can be used to mark
1072
	routes in filters. The default value for new routes is
1073
	<cf/SCOPE_UNIVERSE/.
1074

    
1075
	<tag><m/int/ preference</tag>
1076
	Preference of the route. Valid values are 0-65535. (See the chapter about routing tables.)
1077

    
1078
	<tag><m/ip/ from</tag>
1079
	The router which the route has originated from. Read-only.
1080
	
1081
	<tag><m/ip/ gw</tag>
1082
	Next hop packets routed using this route should be forwarded to.
1083

    
1084
	<tag><m/string/ proto</tag>
1085
	The name of the protocol which the route has been imported from. Read-only.
1086

    
1087
	<tag><m/enum/ source</tag>
1088
	what protocol has told me about this route. Possible values: <cf/RTS_DUMMY/, <cf/RTS_STATIC/, <cf/RTS_INHERIT/, <cf/RTS_DEVICE/, <cf/RTS_STATIC_DEVICE/, <cf/RTS_REDIRECT/, <cf/RTS_RIP/, <cf/RTS_OSPF/, <cf/RTS_OSPF_IA/, <cf/RTS_OSPF_EXT1/, <cf/RTS_OSPF_EXT2/, <cf/RTS_BGP/, <cf/RTS_PIPE/.
1089

    
1090
	<tag><m/enum/ cast</tag>
1091

    
1092
	Route type (Currently <cf/RTC_UNICAST/ for normal routes,
1093
	<cf/RTC_BROADCAST/, <cf/RTC_MULTICAST/, <cf/RTC_ANYCAST/ will
1094
	be used in the future for broadcast, multicast and anycast
1095
	routes). Read-only.
1096

    
1097
	<tag><m/enum/ dest</tag>
1098
	Type of destination the packets should be sent to
1099
	(<cf/RTD_ROUTER/ for forwarding to a neighboring router,
1100
	<cf/RTD_DEVICE/ for routing to a directly-connected network,
1101
	<cf/RTD_MULTIPATH/ for multipath destinations,
1102
	<cf/RTD_BLACKHOLE/ for packets to be silently discarded,
1103
	<cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that
1104
	should be returned with ICMP host unreachable / ICMP
1105
	administratively prohibited messages). Can be changed, but
1106
	only to <cf/RTD_BLACKHOLE/, <cf/RTD_UNREACHABLE/ or
1107
	<cf/RTD_PROHIBIT/.
1108

    
1109
	<tag><m/int/ igp_metric</tag>
1110
	The optional attribute that can be used to specify a distance
1111
	to the network for routes that do not have a native protocol
1112
	metric attribute (like <cf/ospf_metric1/ for OSPF routes). It
1113
	is used mainly by BGP to compare internal distances to boundary
1114
	routers (see below). It is also used when the route is exported
1115
	to OSPF as a default value for OSPF type 1 metric.
1116
</descrip>
1117

    
1118
<p>There also exist some protocol-specific attributes which are described in the corresponding protocol sections.
1119

    
1120
<sect>Other statements
1121

    
1122
<p>The following statements are available:
1123

    
1124
<descrip>
1125
	<tag><m/variable/ = <m/expr/</tag> Set variable to a given value.
1126

    
1127
	<tag>accept|reject [ <m/expr/ ]</tag> Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
1128

    
1129
	<tag>return <m/expr/</tag> Return <cf><m>expr</m></cf> from the current function, the function ends at this point.
1130

    
1131
	<tag>print|printn <m/expr/ [<m/, expr.../]</tag>
1132
	Prints given expressions; useful mainly while debugging
1133
	filters. The <cf/printn/ variant does not terminate the line.
1134

    
1135
	<tag>quitbird</tag>
1136
	Terminates BIRD. Useful when debugging the filter interpreter.
1137
</descrip>
1138

    
1139
<chapt>Protocols
1140

    
1141
<sect>BGP
1142

    
1143
<p>The Border Gateway Protocol is the routing protocol used for backbone
1144
level routing in the today's Internet. Contrary to the other protocols, its convergence
1145
doesn't rely on all routers following the same rules for route selection,
1146
making it possible to implement any routing policy at any router in the
1147
network, the only restriction being that if a router advertises a route,
1148
it must accept and forward packets according to it.
1149

    
1150
<p>BGP works in terms of autonomous systems (often abbreviated as
1151
AS). Each AS is a part of the network with common management and
1152
common routing policy. It is identified by a unique 16-bit number
1153
(ASN).  Routers within each AS usually exchange AS-internal routing
1154
information with each other using an interior gateway protocol (IGP,
1155
such as OSPF or RIP). Boundary routers at the border of
1156
the AS communicate global (inter-AS) network reachability information with
1157
their neighbors in the neighboring AS'es via exterior BGP (eBGP) and
1158
redistribute received information to other routers in the AS via
1159
interior BGP (iBGP).
1160

    
1161
<p>Each BGP router sends to its neighbors updates of the parts of its
1162
routing table it wishes to export along with complete path information
1163
(a list of AS'es the packet will travel through if it uses the particular
1164
route) in order to avoid routing loops.
1165

    
1166
<p>BIRD supports all requirements of the BGP4 standard as defined in
1167
RFC 4271<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4271.txt">
1168
It also supports the community attributes
1169
(RFC 1997<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1997.txt">),
1170
capability negotiation
1171
(RFC 3392<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc3392.txt">),
1172
MD5 password authentication
1173
(RFC 2385<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2385.txt">),
1174
extended communities
1175
(RFC 4360<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4360.txt">),
1176
route reflectors 
1177
(RFC 4456<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4456.txt">),
1178
multiprotocol extensions
1179
(RFC 4760<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4760.txt">),
1180
4B AS numbers 
1181
(RFC 4893<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4893.txt">),
1182
and 4B AS numbers in extended communities
1183
(RFC 5668<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc5668.txt">).
1184

    
1185

    
1186
For IPv6, it uses the standard multiprotocol extensions defined in
1187
RFC 2283<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2283.txt">
1188
including changes described in the
1189
latest draft<htmlurl url="ftp://ftp.rfc-editor.org/internet-drafts/draft-ietf-idr-bgp4-multiprotocol-v2-05.txt">
1190
and applied to IPv6 according to
1191
RFC 2545<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2545.txt">.
1192

    
1193
<sect1>Route selection rules
1194

    
1195
<p>BGP doesn't have any simple metric, so the rules for selection of an optimal
1196
route among multiple BGP routes with the same preference are a bit more complex
1197
and they are implemented according to the following algorithm. It starts the first
1198
rule, if there are more "best" routes, then it uses the second rule to choose
1199
among them and so on.
1200

    
1201
<itemize>
1202
	<item>Prefer route with the highest Local Preference attribute.
1203
	<item>Prefer route with the shortest AS path.
1204
	<item>Prefer IGP origin over EGP and EGP origin over incomplete.
1205
	<item>Prefer the lowest value of the Multiple Exit Discriminator.
1206
	<item>Prefer routes received via eBGP over ones received via iBGP.
1207
	<item>Prefer routes with lower internal distance to a boundary router.
1208
	<item>Prefer the route with the lowest value of router ID of the
1209
	advertising router.
1210
</itemize>
1211

    
1212
<sect1>IGP routing table
1213

    
1214
<p>BGP is mainly concerned with global network reachability and with
1215
routes to other autonomous systems. When such routes are redistributed
1216
to routers in the AS via BGP, they contain IP addresses of a boundary
1217
routers (in route attribute NEXT_HOP). BGP depends on existing IGP
1218
routing table with AS-internal routes to determine immediate next hops
1219
for routes and to know their internal distances to boundary routers
1220
for the purpose of BGP route selection. In BIRD, there is usually
1221
one routing table used for both IGP routes and BGP routes.
1222

    
1223
<sect1>Configuration
1224

    
1225
<p>Each instance of the BGP corresponds to one neighboring router.
1226
This allows to set routing policy and all the other parameters differently
1227
for each neighbor using the following configuration parameters:
1228

    
1229
<descrip>
1230
	<tag>local [<m/ip/] as <m/number/</tag> Define which AS we
1231
	are part of. (Note that contrary to other IP routers, BIRD is
1232
	able to act as a router located in multiple AS'es
1233
	simultaneously, but in such cases you need to tweak the BGP
1234
	paths manually in the filters to get consistent behavior.)
1235
	Optional <cf/ip/ argument specifies a source address,
1236
	equivalent to the <cf/source address/ option (see below).
1237
	This parameter is mandatory.
1238

    
1239
	<tag>neighbor <m/ip/ as <m/number/</tag> Define neighboring router
1240
	this instance will be talking to and what AS it's located in. Unless
1241
	you use the <cf/multihop/ clause, it must be directly connected to one
1242
	of your router's interfaces. In case the neighbor is in the same AS
1243
	as we are, we automatically switch to iBGP. This parameter is mandatory.
1244

    
1245
	<tag>multihop [<m/number/]</tag> Configure multihop BGP
1246
	session to a neighbor that isn't directly connected.
1247
	Accurately, this option should be used if the configured
1248
	neighbor IP address does not match with any local network
1249
	subnets. Such IP address have to be reachable through system
1250
	routing table. For multihop BGP it is recommended to
1251
	explicitly configure <cf/source address/ to have it
1252
	stable. Optional <cf/number/ argument can be used to specify
1253
	the number of hops (used for TTL). Note that the number of
1254
	networks (edges) in a path is counted, i.e. if two BGP
1255
	speakers are separated by one router, the number of hops is
1256
	2. Default: switched off.
1257

    
1258
	<tag>source address <m/ip/</tag> Define local address we
1259
	should use for next hop calculation and as a source address
1260
	for the BGP session. Default: the address of the local
1261
	end of the interface our neighbor is connected to.
1262

    
1263
	<tag>next hop self</tag> Avoid calculation of the Next Hop
1264
	attribute and always advertise our own source address as a
1265
	next hop.  This needs to be used only occasionally to
1266
	circumvent misconfigurations of other routers.  Default:
1267
	disabled.
1268

    
1269
	<tag>missing lladdr self|drop|ignore</tag>Next Hop attribute
1270
	in BGP-IPv6 sometimes contains just the global IPv6 address,
1271
	but sometimes it has to contain both global and link-local
1272
	IPv6 addresses. This option specifies what to do if BIRD have
1273
	to send both addresses but does not know link-local address.
1274
	This situation might happen when routes from other protocols
1275
	are exported to BGP, or when improper updates are received
1276
	from BGP peers.  <cf/self/ means that BIRD advertises its own
1277
	local address instead. <cf/drop/ means that BIRD skips that
1278
	prefixes and logs error. <cf/ignore/ means that BIRD ignores
1279
	the problem and sends just the global address (and therefore
1280
	forms improper BGP update). Default: <cf/self/, unless BIRD
1281
	is configured as a route server (option <cf/rs client/), in
1282
	that case default is <cf/ignore/, because route servers usually
1283
	do not forward packets themselves.
1284

    
1285
	<tag>gateway direct|recursive</tag>For received routes, their
1286
	<cf/gw/ (immediate next hop) attribute is computed from
1287
	received <cf/bgp_next_hop/ attribute. This option specifies
1288
	how it is computed. Direct mode means that the IP address from
1289
	<cf/bgp_next_hop/ is used if it is directly reachable,
1290
	otherwise the neighbor IP address is used. Recursive mode
1291
	means that the gateway is computed by an IGP routing table
1292
	lookup for the IP address from <cf/bgp_next_hop/. Recursive
1293
	mode is the behavior specified by the BGP standard. Direct
1294
	mode is simpler, does not require any routes in a routing
1295
	table, and was used in older versions of BIRD, but does not
1296
	handle well nontrivial iBGP setups and multihop.  Recursive
1297
	mode is incompatible with <ref id="dsc-sorted" name="sorted
1298
	tables">. Default: <cf/direct/ for singlehop eBGP,
1299
	<cf/recursive/ otherwise.
1300

    
1301
	<tag>igp table <m/name/</tag> Specifies a table that is used
1302
	as an IGP routing table. Default: the same as the table BGP is
1303
	connected to.
1304
	
1305
	<tag>ttl security <m/switch/</tag> Use GTSM (RFC 5082 - the
1306
	generalized TTL security mechanism). GTSM protects against
1307
	spoofed packets by ignoring received packets with a smaller
1308
	than expected TTL. To work properly, GTSM have to be enabled
1309
	on both sides of a BGP session. If both <cf/ttl security/ and
1310
	<cf/multihop/ options are enabled, <cf/multihop/ option should
1311
	specify proper hop value to compute expected TTL. Kernel
1312
	support required: Linux: 2.6.34+ (IPv4), 2.6.35+ (IPv6), BSD:
1313
	since long ago, IPv4 only. Note that full (ICMP protection,
1314
	for example) RFC 5082 support is provided by Linux
1315
	only. Default: disabled.
1316
	
1317
	<tag>password <m/string/</tag> Use this password for MD5 authentication
1318
	of BGP sessions. Default: no authentication. Password has to be set by
1319
	external utility (e.g. setkey(8)) on BSD systems.
1320

    
1321
	<tag>passive <m/switch/</tag> Standard BGP behavior is both
1322
        initiating outgoing connections and accepting incoming
1323
        connections. In passive mode, outgoing connections are not
1324
        initiated. Default: off.
1325

    
1326
	<tag>rr client</tag> Be a route reflector and treat the neighbor as
1327
	a route reflection client. Default: disabled.
1328

    
1329
	<tag>rr cluster id <m/IPv4 address/</tag> Route reflectors use cluster id
1330
	to avoid route reflection loops. When there is one route reflector in a cluster
1331
	it usually uses its router id as a cluster id, but when there are more route
1332
	reflectors in a cluster, these need to be configured (using this option) to
1333
	use a common cluster id. Clients in a cluster need not know their cluster
1334
	id and this option is not allowed for them. Default: the same as router id.
1335

    
1336
	<tag>rs client</tag> Be a route server and treat the neighbor
1337
	as a route server client. A route server is used as a
1338
	replacement for full mesh EBGP routing in Internet exchange
1339
	points in a similar way to route reflectors used in IBGP routing.
1340
	BIRD does not implement obsoleted RFC 1863, but uses ad-hoc implementation,
1341
	which behaves like plain EBGP but reduces modifications to advertised route
1342
	attributes to be transparent (for example does not prepend its AS number to
1343
	AS PATH attribute and keeps MED attribute). Default: disabled.
1344

    
1345
	<tag>secondary <m/switch/</tag> Usually, if an import filter
1346
	rejects a selected route, no other route is propagated for
1347
	that network. This option allows to try the next route in
1348
	order until one that is accepted is found or all routes for
1349
	that network are rejected. This can be used for route servers
1350
	that need to propagate different tables to each client but do
1351
	not want to have these tables explicitly (to conserve memory).
1352
	This option requires that the connected routing table is
1353
	<ref id="dsc-sorted" name="sorted">. Default: off.
1354

    
1355
	<tag>enable route refresh <m/switch/</tag> When BGP speaker
1356
	changes its import filter, it has to re-examine all routes
1357
	received from its neighbor against the new filter. As these
1358
	routes might not be available, there is a BGP protocol
1359
	extension Route Refresh (specified in RFC 2918) that allows
1360
	BGP speaker to request re-advertisement of all routes from its
1361
	neighbor. This option specifies whether BIRD advertises this
1362
	capability and accepts such requests. Even when disabled, BIRD
1363
	can send route refresh requests. Default: on.
1364

    
1365
	<tag>interpret communities <m/switch/</tag> RFC 1997 demands
1366
	that BGP speaker should process well-known communities like
1367
	no-export (65535, 65281) or no-advertise (65535, 65282). For
1368
	example, received route carrying a no-adverise community
1369
	should not be advertised to any of its neighbors. If this
1370
	option is enabled (which is by default), BIRD has such
1371
	behavior automatically (it is evaluated when a route is
1372
	exported to the BGP protocol just before the export filter).
1373
	Otherwise, this integrated processing of well-known
1374
	communities is disabled. In that case, similar behavior can be
1375
	implemented in the export filter.  Default: on.
1376

    
1377
	<tag>enable as4 <m/switch/</tag> BGP protocol was designed to use 2B AS numbers
1378
	and was extended later to allow 4B AS number. BIRD supports 4B AS extension,
1379
	but by disabling this option it can be persuaded not to advertise it and
1380
	to maintain old-style sessions with its neighbors. This might be useful for
1381
	circumventing bugs in neighbor's implementation of 4B AS extension.
1382
	Even when disabled (off), BIRD behaves internally as AS4-aware BGP router.
1383
	Default: on.
1384

    
1385
	<tag>capabilities <m/switch/</tag> Use capability advertisement
1386
	to advertise optional capabilities. This is standard behavior
1387
	for newer BGP implementations, but there might be some older
1388
	BGP implementations that reject such connection attempts.
1389
	When disabled (off), features that request it (4B AS support)
1390
	are also disabled. Default: on, with automatic fallback to
1391
	off when received capability-related error.
1392

    
1393
	<tag>advertise ipv4 <m/switch/</tag> Advertise IPv4 multiprotocol capability.
1394
	This is not a correct behavior according to the strict interpretation
1395
	of RFC 4760, but it is widespread and required by some BGP
1396
	implementations (Cisco and Quagga). This option is relevant
1397
	to IPv4 mode with enabled capability advertisement only. Default: on.
1398

    
1399
	<tag>route limit <m/number/</tag> The maximal number of routes
1400
	that may be imported from the protocol. If the route limit is
1401
	exceeded, the connection is closed with error. Limit is currently implemented as
1402
	<cf/import limit number exceed restart/. Default: no limit.
1403

    
1404
	<tag>disable after error <m/switch/</tag> When an error is encountered (either
1405
	locally or by the other side), disable the instance automatically
1406
	and wait for an administrator to fix the problem manually. Default: off.
1407

    
1408
	<tag>hold time <m/number/</tag> Time in seconds to wait for a Keepalive
1409
	message from the other side before considering the connection stale.
1410
	Default: depends on agreement with the neighboring router, we prefer
1411
	240 seconds if the other side is willing to accept it.
1412

    
1413
	<tag>startup hold time <m/number/</tag> Value of the hold timer used
1414
	before the routers have a chance to exchange open messages and agree
1415
	on the real value. Default: 240 seconds.
1416

    
1417
	<tag>keepalive time <m/number/</tag> Delay in seconds between sending
1418
	of two consecutive Keepalive messages. Default: One third of the hold time.
1419

    
1420
	<tag>connect retry time <m/number/</tag> Time in seconds to wait before
1421
	retrying a failed attempt to connect. Default: 120 seconds.
1422

    
1423
	<tag>start delay time <m/number/</tag> Delay in seconds between protocol
1424
	startup and the first attempt to connect. Default: 5 seconds.
1425

    
1426
	<tag>error wait time <m/number/,<m/number/</tag> Minimum and maximum delay in seconds between a protocol
1427
	failure (either local or reported by the peer) and automatic restart.
1428
	Doesn't apply when <cf/disable after error/ is configured. If consecutive
1429
	errors happen, the delay is increased exponentially until it reaches the maximum. Default: 60, 300.
1430

    
1431
	<tag>error forget time <m/number/</tag> Maximum time in seconds between two protocol
1432
	failures to treat them as a error sequence which makes the <cf/error wait time/
1433
	increase exponentially. Default: 300 seconds.
1434

    
1435
	<tag>path metric <m/switch/</tag> Enable comparison of path lengths
1436
	when deciding which BGP route is the best one. Default: on.
1437

    
1438
	<tag>med metric <m/switch/</tag> Enable comparison of MED
1439
	attributes (during best route selection) even between routes
1440
	received from different ASes.  This may be useful if all MED
1441
	attributes contain some consistent metric, perhaps enforced in
1442
	import filters of AS boundary routers. If this option is
1443
	disabled, MED attributes are compared only if routes are
1444
	received from the same AS (which is the standard behavior).
1445
	Default: off.
1446

    
1447
	<tag>deterministic med <m/switch/</tag> BGP route selection
1448
	algorithm is often viewed as a comparison between individual
1449
	routes (e.g. if a new route appears and is better than the
1450
	current best one, it is chosen as the new best one). But the
1451
	proper route selection, as specified by RFC 4271, cannot be
1452
	fully implemented in that way. The problem is mainly in
1453
	handling the MED attribute. BIRD, by default, uses an
1454
	simplification based on individual route comparison, which in
1455
	some cases may lead to temporally dependent behavior (i.e. the
1456
	selection is dependent on the order in which routes appeared).
1457
	This option enables a different (and slower) algorithm
1458
	implementing proper RFC 4271 route selection, which is
1459
	deterministic. Alternative way how to get deterministic
1460
	behavior is to use <cf/med metric/ option. This option is
1461
	incompatible with <ref id="dsc-sorted" name="sorted tables">.
1462
	Default: off.
1463

    
1464
	<tag>igp metric <m/switch/</tag> Enable comparison of internal
1465
 	distances to boundary routers during best route selection. Default: on.
1466

    
1467
	<tag>prefer older <m/switch/</tag> Standard route selection algorithm
1468
	breaks ties by comparing router IDs. This changes the behavior
1469
	to prefer older routes (when both are external and from different
1470
	peer). For details, see RFC 5004. Default: off.
1471

    
1472
	<tag>default bgp_med <m/number/</tag> Value of the Multiple Exit
1473
	Discriminator to be used during route selection when the MED attribute
1474
	is missing. Default: 0.
1475

    
1476
	<tag>default bgp_local_pref <m/number/</tag> A default value
1477
	for the Local Preference attribute. It is used when a new
1478
	Local Preference attribute is attached to a route by the BGP
1479
	protocol itself (for example, if a route is received through
1480
	eBGP and therefore does not have such attribute). Default: 100
1481
	(0 in pre-1.2.0 versions of BIRD).
1482
</descrip>
1483

    
1484
<sect1>Attributes
1485

    
1486
<p>BGP defines several route attributes. Some of them (those marked with `<tt/I/' in the
1487
table below) are available on internal BGP connections only, some of them (marked
1488
with `<tt/O/') are optional.
1489

    
1490
<descrip>
1491
	<tag>bgppath <cf/bgp_path/</tag> Sequence of AS numbers describing the AS path
1492
	the packet will travel through when forwarded according to the particular route.
1493
	In case of internal BGP it doesn't contain the number of the local AS.
1494

    
1495
	<tag>int <cf/bgp_local_pref/ [I]</tag> Local preference value used for
1496
	selection among multiple BGP routes (see the selection rules above). It's
1497
	used as an additional metric which is propagated through the whole local AS.
1498

    
1499
	<tag>int <cf/bgp_med/ [O]</tag> The Multiple Exit Discriminator of the route
1500
	is an optional attribute which is used on external (inter-AS) links to
1501
	convey to an adjacent AS the optimal entry point into the local AS.
1502
	The received attribute is also propagated over internal BGP links.
1503
	The attribute value is zeroed when a route is exported to an external BGP
1504
	instance to ensure that the attribute received from a neighboring AS is
1505
	not propagated to other neighboring ASes. A new value might be set in
1506
	the export filter of an external BGP instance.
1507
	See RFC 4451<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4451.txt">
1508
	for further discussion of BGP MED attribute.
1509

    
1510
	<tag>enum <cf/bgp_origin/</tag> Origin of the route: either <cf/ORIGIN_IGP/
1511
	if the route has originated in an interior routing protocol or
1512
	<cf/ORIGIN_EGP/ if it's been imported from the <tt>EGP</tt> protocol
1513
	(nowadays it seems to be obsolete) or <cf/ORIGIN_INCOMPLETE/ if the origin
1514
	is unknown.
1515

    
1516
	<tag>ip <cf/bgp_next_hop/</tag> Next hop to be used for forwarding of packets
1517
	to this destination. On internal BGP connections, it's an address of the
1518
	originating router if it's inside the local AS or a boundary router the
1519
	packet will leave the AS through if it's an exterior route, so each BGP
1520
	speaker within the AS has a chance to use the shortest interior path
1521
	possible to this point.
1522

    
1523
	<tag>void <cf/bgp_atomic_aggr/ [O]</tag> This is an optional attribute
1524
	which carries no value, but the sole presence of which indicates that the route
1525
	has been aggregated from multiple routes by some router on the path from
1526
	the originator.
1527

    
1528
<!-- we don't handle aggregators right since they are of a very obscure type
1529
	<tag>bgp_aggregator</tag>
1530
-->
1531
	<tag>clist <cf/bgp_community/ [O]</tag> List of community values associated
1532
	with the route. Each such value is a pair (represented as a <cf/pair/ data
1533
	type inside the filters) of 16-bit integers, the first of them containing the number of the AS which defines
1534
	the community and the second one being a per-AS identifier. There are lots
1535
	of uses of the community mechanism, but generally they are used to carry
1536
	policy information like "don't export to USA peers". As each AS can define
1537
	its own routing policy, it also has a complete freedom about which community
1538
	attributes it defines and what will their semantics be.
1539

    
1540
	<tag>eclist <cf/bgp_ext_community/ [O]</tag> List of extended community
1541
	values associated with the route. Extended communities have similar usage
1542
	as plain communities, but they have an extended range (to allow 4B ASNs)
1543
	and a nontrivial structure with a type field. Individual community values are
1544
	represented using an <cf/ec/ data type inside the filters.
1545

    
1546
	<tag>quad <cf/bgp_originator_id/ [I, O]</tag> This attribute is created by the
1547
	route reflector when reflecting the route and contains the router ID of the
1548
	originator of the route in the local AS.
1549

    
1550
	<tag>clist <cf/bgp_cluster_list/ [I, O]</tag> This attribute contains a list
1551
	of cluster IDs of route reflectors. Each route reflector prepends its
1552
	cluster ID when reflecting the route.
1553
</descrip>
1554

    
1555
<sect1>Example
1556

    
1557
<p><code>
1558
protocol bgp {
1559
	local as 65000;			     # Use a private AS number
1560
	neighbor 198.51.100.130 as 64496;    # Our neighbor ...
1561
	multihop;			     # ... which is connected indirectly
1562
	export filter {			     # We use non-trivial export rules
1563
		if source = RTS_STATIC then { # Export only static routes
1564
		        # Assign our community
1565
			bgp_community.add((65000,64501));
1566
			# Artificially increase path length
1567
			# by advertising local AS number twice
1568
			if bgp_path ~ [= 65000 =] then
1569
				bgp_path.prepend(65000);
1570
			accept;
1571
		}
1572
		reject;
1573
	};
1574
	import all;
1575
	source address 198.51.100.14;	# Use a non-standard source address
1576
}
1577
</code>
1578

    
1579
<sect>Device
1580

    
1581
<p>The Device protocol is not a real routing protocol.  It doesn't generate
1582
any routes and it only serves as a module for getting information about network
1583
interfaces from the kernel.
1584

    
1585
<p>Except for very unusual circumstances, you probably should include
1586
this protocol in the configuration since almost all other protocols
1587
require network interfaces to be defined for them to work with.
1588

    
1589
<sect1>Configuration
1590

    
1591
<p><descrip>
1592
	<tag>scan time <m/number/</tag> Time in seconds between two scans
1593
	of the network interface list. On systems where we are notified about
1594
	interface status changes asynchronously (such as newer versions of
1595
	Linux), we need to scan the list only in order to avoid confusion by lost
1596
	notification messages, so the default time is set to a large value.
1597

    
1598
	<tag>primary  [ "<m/mask/" ] <m/prefix/</tag>
1599
	If a network interface has more than one network address, BIRD
1600
	has to choose one of them as a primary one. By default, BIRD
1601
	chooses the lexicographically smallest address as the primary
1602
	one.
1603

    
1604
	This option allows to specify which network address should be
1605
	chosen as a primary one. Network addresses that match
1606
	<m/prefix/ are preferred to non-matching addresses. If more
1607
	<cf/primary/ options are used, the first one has the highest
1608
	preference. If "<m/mask/" is specified, then such
1609
	<cf/primary/ option is relevant only to matching network
1610
	interfaces.
1611

    
1612
	In all cases, an address marked by operating system as
1613
	secondary cannot be chosen as the primary one. 
1614
</descrip>
1615

    
1616
<p>As the Device protocol doesn't generate any routes, it cannot have
1617
any attributes. Example configuration looks like this:
1618

    
1619
<p><code>
1620
protocol device {
1621
	scan time 10;		# Scan the interfaces often
1622
	primary "eth0" 192.168.1.1;
1623
	primary 192.168.0.0/16;
1624
}
1625
</code>
1626

    
1627
<sect>Direct
1628

    
1629
<p>The Direct protocol is a simple generator of device routes for all the
1630
directly connected networks according to the list of interfaces provided
1631
by the kernel via the Device protocol.
1632

    
1633
<p>The question is whether it is a good idea to have such device
1634
routes in BIRD routing table. OS kernel usually handles device routes
1635
for directly connected networks by itself so we don't need (and don't
1636
want) to export these routes to the kernel protocol. OSPF protocol
1637
creates device routes for its interfaces itself and BGP protocol is
1638
usually used for exporting aggregate routes. Although there are some
1639
use cases that use the direct protocol (like abusing eBGP as an IGP
1640
routing protocol), in most cases it is not needed to have these device
1641
routes in BIRD routing table and to use the direct protocol.
1642

    
1643
<p>The only configurable thing about direct is what interfaces it watches:
1644

    
1645
<p><descrip>
1646
	<tag>interface <m/pattern [, ...]/</tag> By default, the Direct
1647
	protocol will generate device routes for all the interfaces
1648
	available. If you want to restrict it to some subset of interfaces
1649
	(for example if you're using multiple routing tables for policy
1650
	routing and some of the policy domains don't contain all interfaces),
1651
	just use this clause.
1652
</descrip>
1653

    
1654
<p>Direct device routes don't contain any specific attributes.
1655

    
1656
<p>Example config might look like this:
1657

    
1658
<p><code>
1659
protocol direct {
1660
	interface "-arc*", "*";		# Exclude the ARCnets
1661
}
1662
</code>
1663

    
1664
<sect>Kernel
1665

    
1666
<p>The Kernel protocol is not a real routing protocol. Instead of communicating
1667
with other routers in the network, it performs synchronization of BIRD's routing
1668
tables with the OS kernel. Basically, it sends all routing table updates to the kernel
1669
and from time to time it scans the kernel tables to see whether some routes have
1670
disappeared (for example due to unnoticed up/down transition of an interface)
1671
or whether an `alien' route has been added by someone else (depending on the
1672
<cf/learn/ switch, such routes are either ignored or accepted to our
1673
table).
1674

    
1675
<p>Unfortunately, there is one thing that makes the routing table
1676
synchronization a bit more complicated. In the kernel routing table
1677
there are also device routes for directly connected networks. These
1678
routes are usually managed by OS itself (as a part of IP address
1679
configuration) and we don't want to touch that.  They are completely
1680
ignored during the scan of the kernel tables and also the export of
1681
device routes from BIRD tables to kernel routing tables is restricted
1682
to prevent accidental interference. This restriction can be disabled using
1683
<cf/device routes/ switch.
1684

    
1685
<p>If your OS supports only a single routing table, you can configure
1686
only one instance of the Kernel protocol. If it supports multiple
1687
tables (in order to allow policy routing; such an OS is for example
1688
Linux), you can run as many instances as you want, but each of them
1689
must be connected to a different BIRD routing table and to a different
1690
kernel table.
1691

    
1692
<p>Because the kernel protocol is partially integrated with the
1693
connected routing table, there are two limitations - it is not
1694
possible to connect more kernel protocols to the same routing table
1695
and changing route destination/gateway in an export
1696
filter of a kernel protocol does not work. Both limitations can be
1697
overcome using another routing table and the pipe protocol.
1698

    
1699
<sect1>Configuration
1700

    
1701
<p><descrip>
1702
	<tag>persist <m/switch/</tag> Tell BIRD to leave all its routes in the
1703
	routing tables when it exits (instead of cleaning them up).
1704
	<tag>scan time <m/number/</tag> Time in seconds between two consecutive scans of the
1705
	kernel routing table.
1706
	<tag>learn <m/switch/</tag> Enable learning of routes added to the kernel
1707
	routing tables by other routing daemons or by the system administrator.
1708
	This is possible only on systems which support identification of route
1709
	authorship.
1710

    
1711
	<tag>device routes <m/switch/</tag> Enable export of device
1712
	routes to the kernel routing table. By default, such routes
1713
	are rejected (with the exception of explicitly configured
1714
	device routes from the static protocol) regardless of the
1715
	export filter to protect device routes in kernel routing table
1716
	(managed by OS itself) from accidental overwriting or erasing.
1717

    
1718
	<tag>kernel table <m/number/</tag> Select which kernel table should
1719
	this particular instance of the Kernel protocol work with. Available
1720
	only on systems supporting multiple routing tables.
1721
</descrip>
1722

    
1723
<sect1>Attributes
1724

    
1725
<p>The Kernel protocol defines several attributes. These attributes
1726
are translated to appropriate system (and OS-specific) route attributes.
1727
We support these attributes:
1728

    
1729
<descrip>
1730
	<tag>int <cf/krt_source/</tag> The original source of the imported
1731
	kernel route.  The value is system-dependent. On Linux, it is
1732
	a value of the protocol field of the route. See
1733
	/etc/iproute2/rt_protos for common values.  On BSD, it is
1734
	based on STATIC and PROTOx flags. The attribute is read-only.
1735

    
1736
	<tag>int <cf/krt_metric/</tag> The kernel metric of
1737
	the route.  When multiple same routes are in a kernel routing
1738
	table, the Linux kernel chooses one with lower metric.
1739

    
1740
	<tag>ip <cf/krt_prefsrc/</tag> (Linux) The preferred source address.
1741
 	Used in source address selection for outgoing packets. Have to
1742
 	be one of IP addresses of the router.
1743

    
1744
	<tag>int <cf/krt_realm/</tag> (Linux) The realm of the route. Can be
1745
	used for traffic classification.
1746
</descrip>
1747

    
1748
<sect1>Example
1749

    
1750
<p>A simple configuration can look this way:
1751

    
1752
<p><code>
1753
protocol kernel {
1754
	export all;
1755
}
1756
</code>
1757

    
1758
<p>Or for a system with two routing tables:
1759

    
1760
<p><code>
1761
protocol kernel {		# Primary routing table
1762
	learn;			# Learn alien routes from the kernel
1763
	persist;		# Don't remove routes on bird shutdown
1764
	scan time 10;		# Scan kernel routing table every 10 seconds
1765
	import all;
1766
	export all;
1767
}
1768

    
1769
protocol kernel {		# Secondary routing table
1770
	table auxtable;
1771
	kernel table 100;
1772
	export all;
1773
}
1774
</code>
1775

    
1776
<sect>OSPF
1777

    
1778
<sect1>Introduction
1779

    
1780
<p>Open Shortest Path First (OSPF) is a quite complex interior gateway
1781
protocol. The current IPv4 version (OSPFv2) is defined in RFC
1782
2328<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2328.txt"> and
1783
the current IPv6 version (OSPFv3) is defined in RFC 5340<htmlurl
1784
url="ftp://ftp.rfc-editor.org/in-notes/rfc5340.txt">  It's a link state
1785
(a.k.a. shortest path first) protocol -- each router maintains a
1786
database describing the autonomous system's topology. Each participating
1787
router has an identical copy of the database and all routers run the
1788
same algorithm calculating a shortest path tree with themselves as a
1789
root. OSPF chooses the least cost path as the best path.
1790

    
1791
<p>In OSPF, the autonomous system can be split to several areas in order
1792
to reduce the amount of resources consumed for exchanging the routing
1793
information and to protect the other areas from incorrect routing data.
1794
Topology of the area is hidden to the rest of the autonomous system.
1795

    
1796
<p>Another very important feature of OSPF is that
1797
it can keep routing information from other protocols (like Static or BGP)
1798
in its link state database as external routes. Each external route can
1799
be tagged by the advertising router, making it possible to pass additional
1800
information between routers on the boundary of the autonomous system.
1801

    
1802
<p>OSPF quickly detects topological changes in the autonomous system (such
1803
as router interface failures) and calculates new loop-free routes after a short
1804
period of convergence. Only a minimal amount of 
1805
routing traffic is involved.
1806

    
1807
<p>Each router participating in OSPF routing periodically sends Hello messages
1808
to all its interfaces. This allows neighbors to be discovered dynamically.
1809
Then the neighbors exchange theirs parts of the link state database and keep it
1810
identical by flooding updates. The flooding process is reliable and ensures
1811
that each router detects all changes.
1812

    
1813
<sect1>Configuration
1814

    
1815
<p>In the main part of configuration, there can be multiple definitions of
1816
OSPF areas, each with a different id. These definitions includes many other
1817
switches and multiple definitions of interfaces. Definition of interface
1818
may contain many switches and constant definitions and list of neighbors
1819
on nonbroadcast networks.
1820

    
1821
<code>
1822
protocol ospf &lt;name&gt; {
1823
	rfc1583compat &lt;switch&gt;;
1824
	tick &lt;num&gt;;
1825
	ecmp &lt;switch&gt; [limit &lt;num&gt;];
1826
	area &lt;id&gt; {
1827
		stub;
1828
		nssa;
1829
		summary &lt;switch&gt;;
1830
		default nssa &lt;switch&gt;;
1831
		default cost &lt;num&gt;;
1832
		default cost2 &lt;num&gt;;
1833
		translator &lt;switch&gt;;
1834
		translator stability &lt;num&gt;;
1835

    
1836
                networks {
1837
			&lt;prefix&gt;;
1838
			&lt;prefix&gt; hidden;
1839
		}
1840
                external {
1841
			&lt;prefix&gt;;
1842
			&lt;prefix&gt; hidden;
1843
			&lt;prefix&gt; tag &lt;num&gt;;
1844
		}
1845
		stubnet &lt;prefix&gt;;
1846
		stubnet &lt;prefix&gt; {
1847
			hidden &lt;switch&gt;;
1848
			summary &lt;switch&gt;;
1849
			cost &lt;num&gt;;
1850
		}
1851
		interface &lt;interface pattern&gt; [instance &lt;num&gt;] {
1852
			cost &lt;num&gt;;
1853
			stub &lt;switch&gt;;
1854
			hello &lt;num&gt;;
1855
			poll &lt;num&gt;;
1856
			retransmit &lt;num&gt;;
1857
			priority &lt;num&gt;;
1858
			wait &lt;num&gt;;
1859
			dead count &lt;num&gt;;
1860
			dead &lt;num&gt;;
1861
			rx buffer [normal|large|&lt;num&gt;];
1862
			type [broadcast|bcast|pointopoint|ptp|
1863
				nonbroadcast|nbma|pointomultipoint|ptmp];
1864
			strict nonbroadcast &lt;switch&gt;;
1865
			real broadcast &lt;switch&gt;;
1866
			check link &lt;switch&gt;;
1867
			ecmp weight &lt;num&gt;;
1868
			authentication [none|simple|cryptographic];
1869
			password "&lt;text&gt;";
1870
			password "&lt;text&gt;" {
1871
				id &lt;num&gt;;
1872
				generate from "&lt;date&gt;";
1873
				generate to "&lt;date&gt;";
1874
				accept from "&lt;date&gt;";
1875
				accept to "&lt;date&gt;";
1876
			};
1877
			neighbors {
1878
				&lt;ip&gt;;
1879
				&lt;ip&gt; eligible;
1880
			};
1881
		};
1882
		virtual link &lt;id&gt; [instance &lt;num&gt;] {
1883
			hello &lt;num&gt;;
1884
			retransmit &lt;num&gt;;
1885
			wait &lt;num&gt;;
1886
			dead count &lt;num&gt;;
1887
			dead &lt;num&gt;;
1888
			authentication [none|simple|cryptographic];
1889
			password "&lt;text&gt;";
1890
		};
1891
	};
1892
}
1893
</code>
1894

    
1895
<descrip>
1896
	<tag>rfc1583compat <M>switch</M></tag>
1897
	 This option controls compatibility of routing table
1898
	 calculation with RFC 1583<htmlurl
1899
	 url="ftp://ftp.rfc-editor.org/in-notes/rfc1583.txt">. Default
1900
	 value is no.
1901

    
1902
	<tag>tick <M>num</M></tag>
1903
	 The routing table calculation and clean-up of areas' databases
1904
         is not performed when a single link state
1905
	 change arrives. To lower the CPU utilization, it's processed later
1906
	 at periodical intervals of <m/num/ seconds. The default value is 1.
1907

    
1908
	<tag>ecmp <M>switch</M> [limit <M>number</M>]</tag>
1909
	 This option specifies whether OSPF is allowed to generate
1910
	 ECMP (equal-cost multipath) routes. Such routes are used when
1911
	 there are several directions to the destination, each with
1912
	 the same (computed) cost. This option also allows to specify
1913
	 a limit on maximal number of nexthops in one route. By
1914
	 default, ECMP is disabled.  If enabled, default value of the
1915
	 limit is 16.
1916

    
1917
	<tag>area <M>id</M></tag>
1918
	 This defines an OSPF area with given area ID (an integer or an IPv4
1919
	 address, similarly to a router ID). The most important area is
1920
	 the backbone (ID 0) to which every other area must be connected.
1921

    
1922
	<tag>stub</tag>
1923
	 This option configures the area to be a stub area. External
1924
	 routes are not flooded into stub areas. Also summary LSAs can be
1925
	 limited in stub areas (see option <cf/summary/).
1926
	 By default, the area is not a stub area.
1927

    
1928
	<tag>nssa</tag>
1929
	 This option configures the area to be a NSSA (Not-So-Stubby
1930
	 Area). NSSA is a variant of a stub area which allows a
1931
	 limited way of external route propagation. Global external
1932
	 routes are not propagated into a NSSA, but an external route
1933
	 can be imported into NSSA as a (area-wide) NSSA-LSA (and
1934
	 possibly translated and/or aggregated on area boundary).
1935
	 By default, the area is not NSSA.
1936

    
1937
	<tag>summary <M>switch</M></tag>
1938
	 This option controls propagation of summary LSAs into stub or
1939
	 NSSA areas. If enabled, summary LSAs are propagated as usual,
1940
	 otherwise just the default summary route (0.0.0.0/0) is
1941
	 propagated (this is sometimes called totally stubby area). If
1942
	 a stub area has more area boundary routers, propagating
1943
	 summary LSAs could lead to more efficient routing at the cost
1944
	 of larger link state database. Default value is no.
1945

    
1946
	<tag>default nssa <M>switch</M></tag>
1947
 	 When <cf/summary/ option is enabled, default summary route is
1948
	 no longer propagated to the NSSA. In that case, this option
1949
	 allows to originate default route as NSSA-LSA to the NSSA.
1950
	 Default value is no.
1951

    
1952
	<tag>default cost <M>num</M></tag>
1953
	 This option controls the cost of a default route propagated to
1954
	 stub and NSSA areas. Default value is 1000.
1955

    
1956
	<tag>default cost2 <M>num</M></tag>
1957
	 When a default route is originated as NSSA-LSA, its cost
1958
	 can use either type 1 or type 2 metric. This option allows
1959
	 to specify the cost of a default route in type 2 metric.
1960
	 By default, type 1 metric (option <cf/default cost/) is used.
1961

    
1962
	<tag>translator <M>switch</M></tag>
1963
	 This option controls translation of NSSA-LSAs into external
1964
	 LSAs. By default, one translator per NSSA is automatically
1965
	 elected from area boundary routers. If enabled, this area
1966
	 boundary router would unconditionally translate all NSSA-LSAs
1967
	 regardless of translator election. Default value is no.
1968

    
1969
	<tag>translator stability <M>num</M></tag>
1970
	 This option controls the translator stability interval (in
1971
	 seconds). When the new translator is elected, the old one
1972
	 keeps translating until the interval is over. Default value
1973
	 is 40.
1974

    
1975
	<tag>networks { <m/set/ }</tag>
1976
         Definition of area IP ranges. This is used in summary LSA origination.
1977
	 Hidden networks are not propagated into other areas.
1978

    
1979
	<tag>external { <m/set/ }</tag>
1980
         Definition of external area IP ranges for NSSAs. This is used
1981
	 for NSSA-LSA translation. Hidden networks are not translated
1982
	 into external LSAs. Networks can have configured route tag.
1983

    
1984
	<tag>stubnet <m/prefix/ { <m/options/ }</tag>
1985
	 Stub networks are networks that are not transit networks
1986
	 between OSPF routers. They are also propagated through an
1987
	 OSPF area as a part of a link state database. By default,
1988
	 BIRD generates a stub network record for each primary network
1989
	 address on each OSPF interface that does not have any OSPF
1990
	 neighbors, and also for each non-primary network address on
1991
	 each OSPF interface. This option allows to alter a set of
1992
	 stub networks propagated by this router. 
1993

    
1994
	 Each instance of this option adds a stub network with given
1995
	 network prefix to the set of propagated stub network, unless
1996
	 option <cf/hidden/ is used. It also suppresses default stub
1997
	 networks for given network prefix. When option
1998
	 <cf/summary/ is used, also default stub networks that are
1999
	 subnetworks of given stub network are suppressed. This might
2000
	 be used, for example, to aggregate generated stub networks.
2001
	 
2002
	<tag>interface <M>pattern</M> [instance <m/num/]</tag>
2003
	 Defines that the specified interfaces belong to the area being defined.
2004
	 See <ref id="dsc-iface" name="interface"> common option for detailed description.
2005
	 In OSPFv3, you can specify instance ID for that interface
2006
	 description, so it is possible to have several instances of
2007
	 that interface with different options or even in different areas.
2008

    
2009
	<tag>virtual link <M>id</M> [instance <m/num/]</tag>
2010
	 Virtual link to router with the router id. Virtual link acts
2011
         as a point-to-point interface belonging to backbone. The
2012
         actual area is used as transport area. This item cannot be in
2013
         the backbone. In OSPFv3, you could also use several virtual
2014
         links to one destination with different instance IDs.
2015

    
2016
	<tag>cost <M>num</M></tag>
2017
	 Specifies output cost (metric) of an interface. Default value is 10.
2018

    
2019
	<tag>stub <M>switch</M></tag>
2020
	 If set to interface it does not listen to any packet and does not send
2021
	 any hello. Default value is no.
2022

    
2023
	<tag>hello <M>num</M></tag>
2024
	 Specifies interval in seconds between sending of Hello messages. Beware, all
2025
	 routers on the same network need to have the same hello interval.
2026
	 Default value is 10.
2027

    
2028
	<tag>poll <M>num</M></tag>
2029
	 Specifies interval in seconds between sending of Hello messages for
2030
	 some neighbors on NBMA network. Default value is 20.
2031

    
2032
	<tag>retransmit <M>num</M></tag>
2033
	 Specifies interval in seconds between retransmissions of unacknowledged updates.
2034
	 Default value is 5.
2035

    
2036
        <tag>priority <M>num</M></tag>
2037
	 On every multiple access network (e.g., the Ethernet) Designed Router
2038
	 and Backup Designed router are elected. These routers have some
2039
	 special functions in the flooding process. Higher priority increases
2040
	 preferences in this election. Routers with priority 0 are not
2041
	 eligible. Default value is 1.
2042

    
2043
	<tag>wait <M>num</M></tag>
2044
	 After start, router waits for the specified number of seconds between starting
2045
	 election and building adjacency. Default value is 40.
2046
	 
2047
	<tag>dead count <M>num</M></tag>
2048
	 When the router does not receive any messages from a neighbor in
2049
	 <m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
2050

    
2051
	<tag>dead <M>num</M></tag>
2052
	 When the router does not receive any messages from a neighbor in
2053
	 <m/dead/ seconds, it will consider the neighbor down. If both directives
2054
	 <m/dead count/ and <m/dead/ are used, <m/dead/ has precendence.
2055

    
2056
	<tag>rx buffer <M>num</M></tag>
2057
	 This sets the size of buffer used for receiving packets. The buffer should
2058
	 be bigger than maximal size of any packets. Value NORMAL (default)
2059
	 means 2*MTU, value LARGE means maximal allowed packet - 65535.
2060

    
2061
	<tag>type broadcast|bcast</tag>
2062
	 BIRD detects a type of a connected network automatically, but
2063
	 sometimes it's convenient to force use of a different type
2064
	 manually. On broadcast networks (like ethernet), flooding
2065
	 and Hello messages are sent using multicasts (a single packet
2066
	 for all the neighbors). A designated router is elected and it
2067
	 is responsible for synchronizing the link-state databases and
2068
	 originating network LSAs. This network type cannot be used on
2069
	 physically NBMA networks and on unnumbered networks (networks
2070
	 without proper IP prefix).
2071

    
2072
	<tag>type pointopoint|ptp</tag>
2073
	 Point-to-point networks connect just 2 routers together. No
2074
	 election is performed and no network LSA is originated, which
2075
	 makes it simpler and faster to establish. This network type
2076
	 is useful not only for physically PtP ifaces (like PPP or
2077
	 tunnels), but also for broadcast networks used as PtP links.
2078
	 This network type cannot be used on physically NBMA networks.
2079

    
2080
	<tag>type nonbroadcast|nbma</tag>
2081
	 On NBMA networks, the packets are sent to each neighbor
2082
	 separately because of lack of multicast capabilities.
2083
	 Like on broadcast networks, a designated router is elected,
2084
	 which plays a central role in propagation of LSAs.
2085
	 This network type cannot be used on unnumbered networks.
2086

    
2087
	<tag>type pointomultipoint|ptmp</tag>
2088
	 This is another network type designed to handle NBMA
2089
	 networks. In this case the NBMA network is treated as a
2090
	 collection of PtP links. This is useful if not every pair of
2091
	 routers on the NBMA network has direct communication, or if
2092
	 the NBMA network is used as an (possibly unnumbered) PtP
2093
	 link.
2094

    
2095
	<tag>strict nonbroadcast <M>switch</M></tag>
2096
	 If set, don't send hello to any undefined neighbor. This switch
2097
	 is ignored on other than NBMA or PtMP networks. Default value is no.
2098

    
2099
	<tag>real broadcast <m/switch/</tag>
2100
	 In <cf/type broadcast/ or <cf/type ptp/ network
2101
	 configuration, OSPF packets are sent as IP multicast
2102
	 packets. This option changes the behavior to using
2103
	 old-fashioned IP broadcast packets. This may be useful as a
2104
	 workaround if IP multicast for some reason does not work or
2105
	 does not work reliably. This is a non-standard option and
2106
	 probably is not interoperable with other OSPF
2107
	 implementations. Default value is no.
2108

    
2109
	<tag>check link <M>switch</M></tag>
2110
	 If set, a hardware link state (reported by OS) is taken into
2111
	 consideration. When a link disappears (e.g. an ethernet cable is
2112
	 unplugged), neighbors are immediately considered unreachable
2113
	 and only the address of the iface (instead of whole network
2114
	 prefix) is propagated. It is possible that some hardware
2115
	 drivers or platforms do not implement this feature. Default value is no.
2116

    
2117
	<tag>ecmp weight <M>num</M></tag>
2118
	 When ECMP (multipath) routes are allowed, this value specifies
2119
	 a relative weight used for nexthops going through the iface.
2120
	 Allowed values are 1-256. Default value is 1.
2121

    
2122
	<tag>authentication none</tag>
2123
	 No passwords are sent in OSPF packets. This is the default value.
2124

    
2125
	<tag>authentication simple</tag>
2126
	 Every packet carries 8 bytes of password. Received packets
2127
	 lacking this password are ignored. This authentication mechanism is
2128
	 very weak.
2129

    
2130
	<tag>authentication cryptographic</tag>
2131
	 16-byte long MD5 digest is appended to every packet. For the digest
2132
         generation 16-byte long passwords are used. Those passwords are 
2133
         not sent via network, so this mechanism is quite secure.
2134
         Packets can still be read by an attacker.
2135

    
2136
	<tag>password "<M>text</M>"</tag>
2137
	 An 8-byte or 16-byte password used for authentication.
2138
	 See <ref id="dsc-pass" name="password"> common option for detailed description.
2139

    
2140
	<tag>neighbors { <m/set/ } </tag>
2141
	 A set of neighbors to which Hello messages on NBMA or PtMP
2142
	 networks are to be sent. For NBMA networks, some of them
2143
	 could be marked as eligible.
2144

    
2145
</descrip>
2146

    
2147
<sect1>Attributes
2148

    
2149
<p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
2150
Metric is ranging from 1 to infinity (65535).
2151
External routes use <cf/metric type 1/ or <cf/metric type 2/.
2152
A <cf/metric of type 1/ is comparable with internal <cf/metric/, a
2153
<cf/metric of type 2/ is always longer
2154
than any <cf/metric of type 1/ or any <cf/internal metric/.
2155
<cf/Internal metric/ or <cf/metric of type 1/ is stored in attribute
2156
<cf/ospf_metric1/, <cf/metric type 2/ is stored in attribute <cf/ospf_metric2/.
2157
If you specify both metrics only metric1 is used.
2158

    
2159
Each external route can also carry attribute <cf/ospf_tag/ which is a
2160
32-bit integer which is used when exporting routes to other protocols;
2161
otherwise, it doesn't affect routing inside the OSPF domain at all.
2162
The fourth attribute <cf/ospf_router_id/ is a router ID of the router
2163
advertising that route/network. This attribute is read-only. Default
2164
is <cf/ospf_metric2 = 10000/ and <cf/ospf_tag = 0/.
2165

    
2166
<sect1>Example
2167

    
2168
<p>
2169

    
2170
<code>
2171
protocol ospf MyOSPF {
2172
        rfc1583compat yes;
2173
        tick 2;
2174
	export filter {
2175
		if source = RTS_BGP then {
2176
			ospf_metric1 = 100;
2177
			accept;
2178
		}
2179
		reject;
2180
	};
2181
	area 0.0.0.0 {
2182
		interface "eth*" {
2183
			cost 11;
2184
			hello 15;
2185
			priority 100;
2186
			retransmit 7;
2187
			authentication simple;
2188
			password "aaa";
2189
		};
2190
		interface "ppp*" {
2191
			cost 100;
2192
			authentication cryptographic;
2193
			password "abc" {
2194
				id 1;
2195
				generate to "22-04-2003 11:00:06";
2196
				accept from "17-01-2001 12:01:05";
2197
			};
2198
			password "def" {
2199
				id 2;
2200
				generate to "22-07-2005 17:03:21";
2201
				accept from "22-02-2001 11:34:06";
2202
			};
2203
		};
2204
		interface "arc0" {
2205
			cost 10;
2206
			stub yes;
2207
		};
2208
		interface "arc1";
2209
	};
2210
	area 120 {
2211
		stub yes;
2212
		networks {
2213
			172.16.1.0/24;
2214
			172.16.2.0/24 hidden;
2215
		}
2216
		interface "-arc0" , "arc*" {
2217
			type nonbroadcast;
2218
			authentication none;
2219
			strict nonbroadcast yes;
2220
			wait 120;
2221
			poll 40;
2222
			dead count 8;
2223
			neighbors {
2224
				192.168.120.1 eligible;
2225
				192.168.120.2;
2226
				192.168.120.10;
2227
			};
2228
		};
2229
	};
2230
}
2231
</code>
2232

    
2233
<sect>Pipe
2234

    
2235
<sect1>Introduction
2236

    
2237
<p>The Pipe protocol serves as a link between two routing tables, allowing routes to be
2238
passed from a table declared as primary (i.e., the one the pipe is connected to using the
2239
<cf/table/ configuration keyword) to the secondary one (declared using <cf/peer table/)
2240
and vice versa, depending on what's allowed by the filters. Export filters control export
2241
of routes from the primary table to the secondary one, import filters control the opposite
2242
direction.
2243

    
2244
<p>The Pipe protocol may work in the transparent mode mode or in the opaque mode.
2245
In the transparent mode, the Pipe protocol retransmits all routes from
2246
one table to the other table, retaining their original source and
2247
attributes.  If import and export filters are set to accept, then both
2248
tables would have the same content. The transparent mode is the default mode.
2249

    
2250
<p>In the opaque mode, the Pipe protocol retransmits optimal route
2251
from one table to the other table in a similar way like other
2252
protocols send and receive routes. Retransmitted route will have the
2253
source set to the Pipe protocol, which may limit access to protocol
2254
specific route attributes. This mode is mainly for compatibility, it
2255
is not suggested for new configs. The mode can be changed by
2256
<tt/mode/ option.
2257

    
2258
<p>The primary use of multiple routing tables and the Pipe protocol is for policy routing,
2259
where handling of a single packet doesn't depend only on its destination address, but also
2260
on its source address, source interface, protocol type and other similar parameters.
2261
In many systems (Linux being a good example), the kernel allows to enforce routing policies
2262
by defining routing rules which choose one of several routing tables to be used for a packet
2263
according to its parameters. Setting of these rules is outside the scope of BIRD's work
2264
(on Linux, you can use the <tt/ip/ command), but you can create several routing tables in BIRD,
2265
connect them to the kernel ones, use filters to control which routes appear in which tables
2266
and also you can employ the Pipe protocol for exporting a selected subset of one table to
2267
another one.
2268

    
2269
<sect1>Configuration
2270

    
2271
<p><descrip>
2272
	<tag>peer table <m/table/</tag> Defines secondary routing table to connect to. The
2273
	primary one is selected by the <cf/table/ keyword.
2274

    
2275
	<tag>mode opaque|transparent</tag> Specifies the mode for the pipe to work in. Default is opaque.
2276
</descrip>
2277

    
2278
<sect1>Attributes
2279

    
2280
<p>The Pipe protocol doesn't define any route attributes.
2281

    
2282
<sect1>Example
2283

    
2284
<p>Let's consider a router which serves as a boundary router of two different autonomous
2285
systems, each of them connected to a subset of interfaces of the router, having its own
2286
exterior connectivity and wishing to use the other AS as a backup connectivity in case
2287
of outage of its own exterior line.
2288

    
2289
<p>Probably the simplest solution to this situation is to use two routing tables (we'll
2290
call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that packets having
2291
arrived from interfaces belonging to the first AS will be routed according to <cf/as1/
2292
and similarly for the second AS. Thus we have split our router to two logical routers,
2293
each one acting on its own routing table, having its own routing protocols on its own
2294
interfaces. In order to use the other AS's routes for backup purposes, we can pass
2295
the routes between the tables through a Pipe protocol while decreasing their preferences
2296
and correcting their BGP paths to reflect the AS boundary crossing.
2297

    
2298
<code>
2299
table as1;				# Define the tables
2300
table as2;
2301

    
2302
protocol kernel kern1 {			# Synchronize them with the kernel
2303
	table as1;
2304
	kernel table 1;
2305
}
2306

    
2307
protocol kernel kern2 {
2308
	table as2;
2309
	kernel table 2;
2310
}
2311

    
2312
protocol bgp bgp1 {			# The outside connections
2313
	table as1;
2314
	local as 1;
2315
	neighbor 192.168.0.1 as 1001;
2316
	export all;
2317
	import all;
2318
}
2319

    
2320
protocol bgp bgp2 {
2321
	table as2;
2322
	local as 2;
2323
	neighbor 10.0.0.1 as 1002;
2324
	export all;
2325
	import all;
2326
}
2327

    
2328
protocol pipe {				# The Pipe
2329
	table as1;
2330
	peer table as2;
2331
	export filter {
2332
		if net ~ [ 1.0.0.0/8+] then {	# Only AS1 networks
2333
			if preference>10 then preference = preference-10;
2334
			if source=RTS_BGP then bgp_path.prepend(1);
2335
			accept;
2336
		}
2337
		reject;
2338
	};
2339
	import filter {
2340
		if net ~ [ 2.0.0.0/8+] then {	# Only AS2 networks
2341
			if preference>10 then preference = preference-10;
2342
			if source=RTS_BGP then bgp_path.prepend(2);
2343
			accept;
2344
		}
2345
		reject;
2346
	};
2347
}
2348
</code>
2349

    
2350
<sect>RAdv
2351

    
2352
<sect1>Introduction
2353

    
2354
<p>The RAdv protocol is an implementation of Router Advertisements,
2355
which are used in the IPv6 stateless autoconfiguration. IPv6 routers
2356
send (in irregular time intervals or as an answer to a request)
2357
advertisement packets to connected networks. These packets contain
2358
basic information about a local network (e.g. a list of network
2359
prefixes), which allows network hosts to autoconfigure network
2360
addresses and choose a default route. BIRD implements router behavior
2361
as defined in
2362
RFC 4861<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4861.txt">
2363
and also the DNS extensions from
2364
RFC 6106<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc6106.txt">.
2365

    
2366
<sect1>Configuration
2367

    
2368
<p>There are several classes of definitions in RAdv configuration --
2369
interface definitions, prefix definitions and DNS definitions:
2370

    
2371
<descrip>
2372
	<tag>interface <m/pattern [, ...]/  { <m/options/ }</tag>
2373
	Interface definitions specify a set of interfaces on which the
2374
	protocol is activated and contain interface specific options.
2375
	See <ref id="dsc-iface" name="interface"> common options for
2376
	detailed description.
2377

    
2378
	<tag>prefix <m/prefix/ { <m/options/ }</tag>
2379
	Prefix definitions allow to modify a list of advertised
2380
	prefixes. By default, the advertised prefixes are the same as
2381
	the network prefixes assigned to the interface. For each
2382
	network prefix, the matching prefix definition is found and
2383
	its options are used. If no matching prefix definition is
2384
	found, the prefix is used with default options.
2385

    
2386
	Prefix definitions can be either global or interface-specific.
2387
	The second ones are part of interface options. The prefix
2388
	definition matching is done in the first-match style, when
2389
	interface-specific definitions are processed before global
2390
	definitions. As expected, the prefix definition is matching if
2391
	the network prefix is a subnet of the prefix in prefix
2392
	definition.
2393

    
2394
	<tag>rdnss { <m/options/ }</tag>
2395
	RDNSS definitions allow to specify a list of advertised
2396
	recursive DNS servers together with their options. As options
2397
	are seldom necessary, there is also a short variant <cf>rdnss
2398
	<m/address/</cf> that just specifies one DNS server. Multiple
2399
	definitions are cumulative. RDNSS definitions may also be
2400
	interface-specific when used inside interface options. By
2401
	default, interface uses both global and interface-specific
2402
	options, but that can be changed by <cf/rdnss local/ option.
2403

    
2404
	<tag>dnssl { <m/options/ }</tag>
2405
	DNSSL definitions allow to specify a list of advertised DNS
2406
	search domains together with their options. Like <cf/rdnss/
2407
	above, multiple definitions are cumulative, they can be used
2408
	also as interface-specific options and there is a short
2409
	variant <cf>dnssl <m/domain/</cf> that just specifies one DNS
2410
        search domain.
2411
</descrip>
2412

    
2413
<p>Interface specific options:
2414

    
2415
<descrip>
2416
	<tag>max ra interval <m/expr/</tag>
2417
	Unsolicited router advertisements are sent in irregular time
2418
	intervals. This option specifies the maximum length of these
2419
	intervals, in seconds. Valid values are 4-1800. Default: 600
2420

    
2421
	<tag>min ra interval <m/expr/</tag>
2422
	This option specifies the minimum length of that intervals, in
2423
	seconds. Must be at least 3 and at most 3/4 * <cf/max ra interval/.
2424
	Default: about 1/3 * <cf/max ra interval/.
2425

    
2426
	<tag>min delay <m/expr/</tag>
2427
	The minimum delay between two consecutive router advertisements,
2428
	in seconds. Default: 3
2429

    
2430
	<tag>managed <m/switch/</tag>
2431
	This option specifies whether hosts should use DHCPv6 for
2432
	IP address configuration. Default: no
2433

    
2434
	<tag>other config <m/switch/</tag>
2435
	This option specifies whether hosts should use DHCPv6 to
2436
	receive other configuration information. Default: no
2437

    
2438
	<tag>link mtu <m/expr/</tag>
2439
	This option specifies which value of MTU should be used by
2440
	hosts. 0 means unspecified. Default: 0
2441

    
2442
	<tag>reachable time <m/expr/</tag>
2443
	This option specifies the time (in milliseconds) how long
2444
	hosts should assume a neighbor is reachable (from the last
2445
	confirmation). Maximum is 3600000, 0 means unspecified.
2446
	Default 0.
2447

    
2448
	<tag>retrans timer <m/expr/</tag>
2449
	This option specifies the time (in milliseconds) how long
2450
	hosts should wait before retransmitting Neighbor Solicitation
2451
	messages. 0 means unspecified. Default 0.
2452

    
2453
	<tag>current hop limit <m/expr/</tag>
2454
	This option specifies which value of Hop Limit should be used
2455
	by hosts. Valid values are 0-255, 0 means unspecified. Default: 64
2456

    
2457
	<tag>default lifetime <m/expr/</tag>
2458
	This option specifies the time (in seconds) how long (after
2459
	the receipt of RA) hosts may use the router as a default
2460
	router. 0 means do not use as a default router. Default: 3 *
2461
	<cf/max ra interval/.
2462

    
2463
	<tag>rdnss local <m/bool/</tag>
2464
	Use only local (interface-specific) RDNSS definitions for this
2465
	interface. Otherwise, both global and local definitions are
2466
	used. Could also be used to disable RDNSS for given interface
2467
	if no local definitons are specified. Default: no.
2468

    
2469
	<tag>dnssl local <m/bool/</tag>
2470
	Use only local DNSSL definitions for this interface. See
2471
	<cf/rdnss local/ option above. Default: no.
2472
</descrip>
2473

    
2474

    
2475
<p>Prefix specific options:
2476

    
2477
<descrip>
2478
	<tag>onlink <m/switch/</tag>
2479
	This option specifies whether hosts may use the advertised
2480
	prefix for onlink determination. Default: yes
2481

    
2482
	<tag>autonomous <m/switch/</tag>
2483
	This option specifies whether hosts may use the advertised
2484
	prefix for stateless autoconfiguration. Default: yes
2485

    
2486
	<tag>valid lifetime <m/expr/</tag>
2487
	This option specifies the time (in seconds) how long (after
2488
	the receipt of RA) the prefix information is valid, i.e.,
2489
	autoconfigured IP addresses can be assigned and hosts with
2490
	that IP addresses are considered directly reachable. 0 means
2491
	the prefix is no longer valid. Default: 86400 (1 day)
2492

    
2493
	<tag>preferred lifetime <m/expr/</tag>
2494
	This option specifies the time (in seconds) how long (after
2495
	the receipt of RA) IP addresses generated from the prefix
2496
	using stateless autoconfiguration remain preferred. Default:
2497
	14400 (4 hours)
2498
</descrip>
2499

    
2500

    
2501
<p>RDNSS specific options:
2502

    
2503
<descrip>
2504
	<tag>ns <m/address/</tag>
2505
	This option specifies one recursive DNS server. Can be used
2506
	multiple times for multiple servers. It is mandatory to have
2507
	at least one <cf/ns/ option in <cf/rdnss/ definition.
2508

    
2509
	<tag>lifetime [mult] <m/expr/</tag>
2510
	This option specifies the time how long the RDNSS information
2511
        may be used by clients after the receipt of RA. It is
2512
        expressed either in seconds or (when <cf/mult/ is used) in
2513
        multiples of <cf/max ra interval/. Note that RDNSS information
2514
        is also invalidated when <cf/default lifetime/ expires. 0
2515
        means these addresses are no longer valid DNS servers.
2516
	Default: 3 * <cf/max ra interval/.
2517
</descrip>
2518

    
2519

    
2520
<p>DNSSL specific options:
2521

    
2522
<descrip>
2523
	<tag>domain <m/address/</tag>
2524
	This option specifies one DNS search domain. Can be used
2525
	multiple times for multiple domains. It is mandatory to have
2526
	at least one <cf/domain/ option in <cf/dnssl/ definition.
2527

    
2528
	<tag>lifetime [mult] <m/expr/</tag>
2529
	This option specifies the time how long the DNSSL information
2530
        may be used by clients after the receipt of RA. Details are
2531
	the same as for RDNSS <cf/lifetime/ option above.
2532
	Default: 3 * <cf/max ra interval/.
2533
</descrip>
2534

    
2535

    
2536
<sect1>Example
2537

    
2538
<p><code>
2539
protocol radv {
2540
	interface "eth2" {
2541
		max ra interval 5;	# Fast failover with more routers
2542
		managed yes;		# Using DHCPv6 on eth2
2543
		prefix ::/0 {
2544
			autonomous off;	# So do not autoconfigure any IP
2545
		};
2546
	};
2547

    
2548
	interface "eth*";		# No need for any other options
2549

    
2550
	prefix 2001:0DB8:1234::/48 {
2551
		preferred lifetime 0;	# Deprecated address range
2552
	};
2553

    
2554
	prefix 2001:0DB8:2000::/48 {
2555
		autonomous off;		# Do not autoconfigure
2556
	};
2557

    
2558
	rdnss 2001:0DB8:1234::10;	# Short form of RDNSS
2559

    
2560
	rdnss {
2561
		lifetime mult 10;
2562
		ns 2001:0DB8:1234::11;
2563
		ns 2001:0DB8:1234::12;
2564
	};
2565

    
2566
	dnssl {
2567
		lifetime 3600;
2568
		domain "abc.com";
2569
		domain "xyz.com";
2570
	};
2571
}
2572
</code>
2573

    
2574
<sect>RIP
2575

    
2576
<sect1>Introduction
2577

    
2578
<p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol, where each router broadcasts (to all its neighbors)
2579
distances to all networks it can reach. When a router hears distance to another network, it increments
2580
it and broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some network goes
2581
unreachable, routers keep telling each other that its distance is the original distance plus 1 (actually, plus
2582
interface metric, which is usually one). After some time, the distance reaches infinity (that's 15 in
2583
RIP) and all routers know that network is unreachable. RIP tries to minimize situations where
2584
counting to infinity is necessary, because it is slow. Due to infinity being 16, you can't use
2585
RIP on networks where maximal distance is higher than 15 hosts. You can read more about RIP at <HTMLURL
2586
URL="http://www.ietf.org/html.charters/rip-charter.html" name="http://www.ietf.org/html.charters/rip-charter.html">. Both IPv4  
2587
(RFC 1723<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1723.txt">)
2588
and IPv6 (RFC 2080<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2080.txt">) versions of RIP are supported by BIRD, historical RIPv1 (RFC 1058<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1058.txt">)is
2589
not currently supported. RIPv4 MD5 authentication (RFC 2082<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2082.txt">) is supported.
2590

    
2591
<p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
2592
convergence, big network load and inability to handle larger networks
2593
makes it pretty much obsolete. (It is still usable on very small networks.)
2594

    
2595
<sect1>Configuration
2596

    
2597
<p>In addition to options common for all to other protocols, RIP supports the following ones:
2598

    
2599
<descrip>
2600
	<tag/authentication none|plaintext|md5/ selects authentication method to be used. <cf/none/ means that
2601
	  packets are not authenticated at all, <cf/plaintext/ means that a plaintext password is embedded
2602
	  into each packet, and <cf/md5/ means that packets are authenticated using a MD5 cryptographic
2603
	  hash. If you set authentication to not-none, it is a good idea to add <cf>password</cf>
2604
	  section. Default: none.
2605

    
2606
	<tag>honor always|neighbor|never </tag>specifies when should requests for dumping routing table
2607
	  be honored. (Always, when sent from a  host on a directly connected
2608
	  network or never.) Routing table updates are honored only from
2609
	  neighbors, that is not configurable. Default: never.
2610
</descrip>
2611

    
2612
<p>There are two options that can be specified per-interface. First is <cf>metric</cf>, with
2613
default one.  Second is <cf>mode multicast|broadcast|quiet|nolisten|version1</cf>, it selects mode for
2614
rip to work in. If nothing is specified, rip runs in multicast mode. <cf>version1</cf> is
2615
currently equivalent to <cf>broadcast</cf>, and it makes RIP talk to a broadcast address even
2616
through multicast mode is possible. <cf>quiet</cf> option means that RIP will not transmit
2617
any periodic messages to this interface and <cf>nolisten</cf> means that RIP will send to this
2618
interface but not listen to it.
2619

    
2620
<p>The following options generally override behavior specified in RFC. If you use any of these
2621
options, BIRD will no longer be RFC-compliant, which means it will not be able to talk to anything
2622
other than equally configured BIRD. I have warned you.
2623

    
2624
<descrip>
2625
	<tag>port <M>number</M></tag>
2626
	  selects IP port to operate on, default 520. (This is useful when testing BIRD, if you
2627
	  set this to an address &gt;1024, you will not need to run bird with UID==0).
2628

    
2629
	<tag>infinity <M>number</M></tag>
2630
	  selects the value of infinity, default is 16. Bigger values will make protocol convergence
2631
	  even slower.
2632

    
2633
	<tag>period <M>number</M>
2634
	  </tag>specifies the number of seconds between periodic updates. Default is 30 seconds. A lower
2635
	  number will mean faster convergence but bigger network
2636
	  load. Do not use values lower than 10.
2637

    
2638
	<tag>timeout time <M>number</M>
2639
	  </tag>specifies how old route has to be to be considered unreachable. Default is 4*<cf/period/.
2640

    
2641
	<tag>garbage time <M>number</M>
2642
	  </tag>specifies how old route has to be to be discarded. Default is 10*<cf/period/.
2643
</descrip>
2644

    
2645
<sect1>Attributes
2646

    
2647
<p>RIP defines two route attributes:
2648

    
2649
<descrip>
2650
	<tag>int <cf/rip_metric/</tag> RIP metric of the route (ranging from 0 to <cf/infinity/).
2651
	When routes from different RIP instances are available and all of them have the same
2652
	preference, BIRD prefers the route with lowest <cf/rip_metric/.
2653
	When importing a non-RIP route, the metric defaults to 5.
2654

    
2655
	<tag>int <cf/rip_tag/</tag> RIP route tag: a 16-bit number which can be used
2656
	to carry additional information with the route (for example, an originating AS number
2657
	in case of external routes). When importing a non-RIP route, the tag defaults to 0.
2658
</descrip>
2659

    
2660
<sect1>Example
2661

    
2662
<p><code>
2663
protocol rip MyRIP_test {
2664
        debug all;
2665
        port 1520;
2666
        period 10;
2667
        garbage time 60;
2668
        interface "eth0" { metric 3; mode multicast; };
2669
	interface "eth*" { metric 2; mode broadcast; };
2670
        honor neighbor;
2671
        authentication none;
2672
        import filter { print "importing"; accept; };
2673
        export filter { print "exporting"; accept; };
2674
}
2675
</code>
2676

    
2677
<sect>Static
2678

    
2679
<p>The Static protocol doesn't communicate with other routers in the network,
2680
but instead it allows you to define routes manually. This is often used for
2681
specifying how to forward packets to parts of the network which don't use
2682
dynamic routing at all and also for defining sink routes (i.e., those
2683
telling to return packets as undeliverable if they are in your IP block,
2684
you don't have any specific destination for them and you don't want to send
2685
them out through the default route to prevent routing loops).
2686

    
2687
<p>There are five types of static routes: `classical' routes telling
2688
to forward packets to a neighboring router, multipath routes
2689
specifying several (possibly weighted) neighboring routers, device
2690
routes specifying forwarding to hosts on a directly connected network,
2691
recursive routes computing their nexthops by doing route table lookups
2692
for a given IP and special routes (sink, blackhole etc.) which specify
2693
a special action to be done instead of forwarding the packet.
2694

    
2695
<p>When the particular destination is not available (the interface is down or
2696
the next hop of the route is not a neighbor at the moment), Static just
2697
uninstalls the route from the table it is connected to and adds it again as soon
2698
as the destination becomes adjacent again.
2699

    
2700
<p>The Static protocol does not have many configuration options. The
2701
definition of the protocol contains mainly a list of static routes:
2702

    
2703
<descrip>
2704
	<tag>route <m/prefix/ via <m/ip/</tag> Static route through
2705
	a neighboring router.
2706
	<tag>route <m/prefix/ multipath via <m/ip/ [weight <m/num/] [via ...]</tag>
2707
	Static multipath route. Contains several nexthops (gateways), possibly
2708
 	with their weights.
2709
	<tag>route <m/prefix/ via <m/"interface"/</tag> Static device
2710
	route through an interface to hosts on a directly connected network.
2711
	<tag>route <m/prefix/ recursive <m/ip/</tag> Static recursive route,
2712
	its nexthop depends on a route table lookup for given IP address.
2713
	<tag>route <m/prefix/ drop|reject|prohibit</tag> Special routes
2714
	specifying to drop the packet, return it as unreachable or return
2715
	it as administratively prohibited.
2716

    
2717
	<tag>check link <m/switch/</tag>
2718
	If set, hardware link states of network interfaces are taken
2719
	into consideration.  When link disappears (e.g. ethernet cable
2720
	is unplugged), static routes directing to that interface are
2721
	removed. It is possible that some hardware drivers or
2722
	platforms do not implement this feature. Default: off.
2723

    
2724
	<tag>igp table <m/name/</tag> Specifies a table that is used
2725
	for route table lookups of recursive routes. Default: the
2726
	same table as the protocol is connected to.
2727
</descrip>
2728

    
2729
<p>Static routes have no specific attributes.
2730

    
2731
<p>Example static config might look like this:
2732

    
2733
<p><code>
2734
protocol static {
2735
	table testable;			 # Connect to a non-default routing table
2736
	route 0.0.0.0/0 via 198.51.100.130; # Default route
2737
	route 10.0.0.0/8 multipath	 # Multipath route
2738
		via 198.51.100.10 weight 2
2739
		via 198.51.100.20
2740
		via 192.0.2.1;
2741
	route 203.0.113.0/24 reject;	 # Sink route
2742
	route 10.2.0.0/24 via "arc0";	 # Secondary network
2743
}
2744
</code>
2745

    
2746
<chapt>Conclusions
2747

    
2748
<sect>Future work
2749

    
2750
<p>Although BIRD supports all the commonly used routing protocols,
2751
there are still some features which would surely deserve to be
2752
implemented in future versions of BIRD:
2753

    
2754
<itemize>
2755
<item>Opaque LSA's
2756
<item>Route aggregation and flap dampening
2757
<item>Multipath routes
2758
<item>Multicast routing protocols
2759
<item>Ports to other systems
2760
</itemize>
2761

    
2762
<sect>Getting more help
2763

    
2764
<p>If you use BIRD, you're welcome to join the bird-users mailing list
2765
(<HTMLURL URL="mailto:bird-users@bird.network.cz" name="bird-users@bird.network.cz">)
2766
where you can share your experiences with the other users and consult
2767
your problems with the authors. To subscribe to the list, just send a
2768
<tt/subscribe bird-users/ command in a body of a mail to
2769
(<HTMLURL URL="mailto:majordomo@bird.network.cz" name="majordomo@bird.network.cz">).
2770
The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
2771

    
2772
<p>BIRD is a relatively young system and it probably contains some
2773
bugs. You can report any problems to the bird-users list and the authors
2774
will be glad to solve them, but before you do so,
2775
please make sure you have read the available documentation and that you are running the latest version (available at <HTMLURL
2776
URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">). (Of course, a patch
2777
which fixes the bug is always welcome as an attachment.)
2778

    
2779
<p>If you want to understand what is going inside, Internet standards are
2780
a good and interesting reading. You can get them from <HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or a nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc" name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
2781

    
2782
<p><it/Good luck!/
2783

    
2784
</book>
2785

    
2786
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2787
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