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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>
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 	Set BIRD's router ID. It's a world-wide unique identification
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	of your router, usually one of router's IPv4 addresses.
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	Default: in IPv4 version, the lowest IP address of a
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	non-loopback interface. In IPv6 version, this option is
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	mandatory.
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	<tag>router id from [-] [ "<m/mask/" ] [ <m/prefix/ ] [, ...]</tag>
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	Set BIRD's router ID based on an IP address of an interface
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	specified by an interface pattern. The option is applicable
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	for IPv4 version only. See <ref id="dsc-iface" name="interface">
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	section for detailed description of interface patterns.
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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 keep filtered <m/bool/</tag>
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	Usually, if an import filter rejects a route, the route is
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	forgotten. When this option is active, these routes are
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	kept in the routing table, but they are hidden and not
477
	propagated to other protocols. But it is possible to show them
478
	using <cf/show route filtered/. Note that this option does not
479
	work for the pipe protocol. Default: off.
480

    
481
	<tag>import limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
482
	Specify an import route limit (a maximum number of routes
483
	imported from the protocol) and optionally the action to be
484
	taken when the limit is hit. Warn action just prints warning
485
	log message. Block action discards new routes coming from the
486
	protocol. Restart and disable actions shut the protocol down
487
	like appropriate commands. Disable is the default action if an
488
	action is not explicitly specified. Note that limits are reset
489
	during protocol reconfigure, reload or restart. Default: <cf/off/.
490

    
491
	<tag>receive limit [<m/number/ | off ] [action warn | block | restart | disable]</tag>
492
	Specify an receive route limit (a maximum number of routes
493
	received from the protocol and remembered). It works almost
494
	identically to <cf>import limit</cf> option, the only
495
	difference is that if <cf/import keep filtered/ option is
496
	active, filtered routes are counted towards the limit and
497
	blocked routes are forgotten, as the main purpose of the
498
	receive limit is to protect routing tables from
499
	overflow. Import limit, on the contrary, counts accepted
500
	routes only and routes blocked by the limit are handled like
501
	filtered routes. Default: <cf/off/.
502

    
503
	<tag>export limit [ <m/number/ | off ] [action warn | block | restart | disable]</tag>
504
	Specify an export route limit, works similarly to
505
	the <cf>import limit</cf> option, but for the routes exported
506
	to the protocol. This option is experimental, there are some
507
	problems in details of its behavior -- the number of exported
508
	routes can temporarily exceed the limit without triggering it
509
	during protocol reload, exported routes counter ignores route
510
	blocking and block action also blocks route updates of already
511
	accepted routes -- and these details will probably change in
512
	the future. Default: <cf/off/.
513

    
514
	<tag>description "<m/text/"</tag> This is an optional
515
	description of the protocol. It is displayed as a part of the
516
	output of 'show route all' command.
517

    
518
	<tag>table <m/name/</tag> Connect this protocol to a non-default routing table.
519
</descrip>
520

    
521
<p>There are several options that give sense only with certain protocols:
522

    
523
<descrip>
524
	<tag><label id="dsc-iface">interface [-] [ "<m/mask/" ] [ <m/prefix/ ] [, ...] [ { <m/option/ ; [...] } ]</tag>
525

    
526
	Specifies a set of interfaces on which the protocol is activated with
527
	given interface-specific options. A set of interfaces specified by one
528
	interface option is described using an interface pattern. The
529
	interface pattern consists of a sequence of clauses (separated by
530
	commas), each clause may contain a mask, a prefix, or both of them. An
531
	interface matches the clause if its name matches the mask (if
532
	specified) and its address matches the prefix (if specified). Mask is
533
	specified as shell-like pattern. For IPv6, the prefix part of a clause
534
	is generally ignored and interfaces are matched just by their name.
535

    
536
	An interface matches the pattern if it matches any of its
537
	clauses. If the clause begins with <cf/-/, matching interfaces are
538
	excluded. Patterns are parsed left-to-right, thus
539
	<cf/interface "eth0", -"eth*", "*";/ means eth0 and all
540
	non-ethernets.
541

    
542
	An interface option can be used more times with different
543
	interfaces-specific options, in that case for given interface
544
	the first matching interface option is used.
545
	
546
	This option is allowed in Direct, OSPF, RIP and RAdv protocols,
547
	but in OSPF protocol it is used in <cf/area/ subsection.
548

    
549
	Default: none.
550

    
551
	Examples:
552

    
553
	<cf>interface "*" { type broadcast; };</cf> - start the protocol on all interfaces with
554
	<cf>type broadcast</cf> option.
555

    
556
	<cf>interface "eth1", "eth4", "eth5" { type ptp; };</cf> - start the protocol
557
	on enumerated interfaces with <cf>type ptp</cf> option.
558
	
559
	<cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol on all
560
	interfaces that have address from 192.168.0.0/16, but not
561
	from 192.168.1.0/24.
562

    
563
	<cf>interface -192.168.1.0/24, 192.168.0.0/16;</cf> - start the protocol on all
564
	interfaces that have address from 192.168.0.0/16, but not
565
	from 192.168.1.0/24.
566

    
567
	<cf>interface "eth*" 192.168.1.0/24;</cf> - start the protocol on all
568
	ethernet interfaces that have address from 192.168.1.0/24.
569

    
570
	<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>
571
	Specifies a password that can be used by the protocol. Password option can
572
	be used more times to specify more passwords. If more passwords are
573
	specified, it is a protocol-dependent decision which one is really
574
	used. Specifying passwords does not mean that authentication is
575
	enabled, authentication can be enabled by separate, protocol-dependent
576
	<cf/authentication/ option.
577
	
578
	This option is allowed in OSPF and RIP protocols. BGP has also
579
	<cf/password/ option, but it is slightly different and described
580
	separately.
581

    
582
	Default: none.
583
</descrip>
584

    
585
<p>Password option can contain section with some (not necessary all) password sub-options:
586

    
587
<descrip>
588
	<tag>id <M>num</M></tag>
589
	 ID of the password, (0-255). If it's not used, BIRD will choose
590
	 ID based on an order of the password item in the interface. For
591
	 example, second password item in one interface will have default
592
	 ID 2. ID is used by some routing protocols to identify which
593
	 password was used to authenticate protocol packets.
594

    
595
	<tag>generate from "<m/time/"</tag>
596
	 The start time of the usage of the password for packet signing.
597
	 The format of <cf><m/time/</cf> is <tt>dd-mm-yyyy HH:MM:SS</tt>.
598

    
599
	<tag>generate to "<m/time/"</tag>
600
	 The last time of the usage of the password for packet signing.
601

    
602
	<tag>accept from "<m/time/"</tag>
603
	 The start time of the usage of the password for packet verification.
604

    
605
	<tag>accept to "<m/time/"</tag>
606
	 The last time of the usage of the password for packet verification.
607
</descrip>
608

    
609
<chapt>Remote control
610

    
611
<p>You can use the command-line client <file>birdc</file> to talk with
612
a running BIRD. Communication is done using a <file/bird.ctl/ UNIX
613
domain socket (unless changed with the <tt/-s/ option given to both
614
the server and the client). The commands can perform simple actions
615
such as enabling/disabling of protocols, telling BIRD to show various
616
information, telling it to show routing table filtered by filter, or
617
asking BIRD to reconfigure. Press <tt/?/ at any time to get online
618
help. Option <tt/-r/ can be used to enable a restricted mode of BIRD
619
client, which allows just read-only commands (<cf/show .../). Option
620
<tt/-v/ can be passed to the client, to make it dump numeric return
621
codes along with the messages. You do not necessarily need to use
622
<file/birdc/ to talk to BIRD, your own applications could do that, too
623
-- the format of communication between BIRD and <file/birdc/ is stable
624
(see the programmer's documentation).
625

    
626
<p>There is also lightweight variant of BIRD client called
627
<file/birdcl/, which does not support command line editing and history
628
and has minimal dependencies. This is useful for running BIRD in
629
resource constrained environments, where Readline library (required
630
for regular BIRD client) is not available.
631

    
632
<p>Many commands have the <m/name/ of the protocol instance as an argument.
633
This argument can be omitted if there exists only a single instance.
634

    
635
<p>Here is a brief list of supported functions:
636

    
637
<descrip>
638
	<tag>dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
639
	Dump contents of internal data structures to the debugging output.
640

    
641
	<tag>show status</tag>
642
	Show router status, that is BIRD version, uptime and time from last reconfiguration.
643

    
644
	<tag>show protocols [all]</tag>
645
	Show list of protocol instances along with tables they are connected to and protocol status, possibly giving verbose information, if <cf/all/ is specified.
646

    
647
	<tag>show ospf interface [<m/name/] ["<m/interface/"]</tag>
648
	Show detailed information about OSPF interfaces.
649

    
650
	<tag>show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
651
	Show a list of OSPF neighbors and a state of adjacency to them.
652

    
653
	<tag>show ospf state [all] [<m/name/]</tag>
654
	Show detailed information about OSPF areas based on a content
655
	of the link-state database. It shows network topology, stub
656
	networks, aggregated networks and routers from other areas and
657
	external routes. The command shows information about reachable
658
	network nodes, use option <cf/all/ to show information about
659
	all network nodes in the link-state database.
660

    
661
	<tag>show ospf topology [all] [<m/name/]</tag>
662
	Show a topology of OSPF areas based on a content of the
663
	link-state database.  It is just a stripped-down version of
664
	'show ospf state'.
665

    
666
	<tag>show ospf lsadb [global | area <m/id/ | link] [type <m/num/] [lsid <m/id/] [self | router <m/id/] [<m/name/] </tag>
667
	Show contents of an OSPF LSA database. Options could be used to filter entries.
668

    
669
	<tag>show static [<m/name/]</tag>
670
	Show detailed information about static routes.
671

    
672
	<tag>show interfaces [summary]</tag>
673
	Show the list of interfaces. For each interface, print its type, state, MTU and addresses assigned. 
674

    
675
	<tag>show symbols [table|filter|function|protocol|template|roa|<m/symbol/]</tag>
676
	Show the list of symbols defined in the configuration (names of protocols, routing tables etc.).
677

    
678
	<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>
679
	Show contents of a routing table (by default of the main one or
680
        the table attached to a respective protocol),
681
	that is routes, their metrics and (in case the <cf/all/ switch is given)
682
	all their attributes.
683

    
684
	<p>You can specify a <m/prefix/ if you want to print routes for a
685
	specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
686
	the entry which will be used for forwarding of packets to the given
687
	destination. By default, all routes for each network are printed with
688
	the selected one at the top, unless <cf/primary/ is given in which case
689
	only the selected route is shown.
690

    
691
	<p>You can also ask for printing only routes processed and accepted by
692
	a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
693
	</cf> or matching a given condition (<cf>where <m/condition/</cf>).
694
	The <cf/export/ and <cf/preexport/ switches ask for printing of entries
695
	that are exported to the specified protocol. With <cf/preexport/, the
696
	export filter of the protocol is skipped.
697

    
698
	<p>You can also select just routes added by a specific protocol.
699
	<cf>protocol <m/p/</cf>.
700

    
701
	<p>If BIRD is configured to keep filtered routes (see <cf/import keep filtered/
702
	option), you can show them instead of routes by using <cf/filtered/ switch.
703

    
704
	<p>The <cf/stats/ switch requests showing of route statistics (the
705
	number of networks, number of routes before and after filtering). If
706
	you use <cf/count/ instead, only the statistics will be printed.
707

    
708
	<tag>show roa [<m/prefix/ | in <m/prefix/ | for <m/prefix/] [as <m/num/] [table <m/t/>]</tag>
709
	Show contents of a ROA table (by default of the first one).
710
	You can specify a <m/prefix/ to print ROA entries for a
711
	specific network. If you use <cf>for <m/prefix/</cf>, you'll
712
	get all entries relevant for route validation of the network
713
	prefix; i.e., ROA entries whose prefixes cover the network
714
	prefix. Or you can use <cf>in <m/prefix/</cf> to get ROA entries
715
	covered by the network prefix. You could also use <cf/as/ option
716
	to show just entries for given AS.
717

    
718
	<tag>add roa <m/prefix/ max <m/num/] as <m/num/ [table <m/t/>]</tag>
719
	Add a new ROA entry to a ROA table. Such entry is called
720
	<it/dynamic/ compared to <it/static/ entries specified in the
721
	config file. These dynamic entries survive reconfiguration.
722

    
723
	<tag>delete roa <m/prefix/ max <m/num/] as <m/num/ [table <m/t/>]</tag>
724
	Delete the specified ROA entry from a ROA table. Only dynamic
725
	ROA entries (i.e., the ones added by <cf/add roa/ command) can
726
	be deleted.
727

    
728
	<tag>flush roa [table <m/t/>]</tag>
729
	Remove all dynamic ROA entries from a ROA table.
730

    
731
	<tag>configure [soft] ["<m/config file/"] [timeout [<m/num/]]</tag>
732
	Reload configuration from a given file. BIRD will smoothly
733
	switch itself to the new configuration, protocols are
734
	reconfigured if possible, restarted otherwise. Changes in
735
	filters usually lead to restart of affected protocols.
736

    
737
	If <cf/soft/ option is used, changes in filters does not cause
738
	BIRD to restart affected protocols, therefore already accepted
739
	routes (according to old filters) would be still propagated,
740
	but new routes would be processed according to the new
741
	filters.
742

    
743
	If <cf/timeout/ option is used, config timer is activated. The
744
	new configuration could be either confirmed using
745
	<cf/configure confirm/ command, or it will be reverted to the
746
	old one when the config timer expires. This is useful for cases
747
	when reconfiguration breaks current routing and a router becames
748
	inaccessible for an administrator. The config timeout expiration is
749
	equivalent to <cf/configure undo/ command. The timeout duration
750
	could be specified, default is 300 s.
751

    
752
	<tag>configure confirm</tag>
753
	Deactivate the config undo timer and therefore confirm the current
754
	configuration.
755

    
756
	<tag>configure undo</tag>
757
	Undo the last configuration change and smoothly switch back to
758
	the previous (stored) configuration. If the last configuration
759
	change was soft, the undo change is also soft. There is only
760
	one level of undo, but in some specific cases when several
761
	reconfiguration requests are given immediately in a row and
762
	the intermediate ones are skipped then the undo also skips them back.
763

    
764
	<tag>configure check ["<m/config file/"]</tag>
765
	Read and parse given config file, but do not use it. useful
766
	for checking syntactic and some semantic validity of an config
767
	file.
768

    
769
	<tag>enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
770
	Enable, disable or restart a given protocol instance,
771
	instances matching the <cf><m/pattern/</cf> or
772
	<cf/all/ instances.
773

    
774
	<tag>reload [in|out] <m/name/|"<m/pattern/"|all</tag>
775
	
776
	Reload a given protocol instance, that means re-import routes
777
	from the protocol instance and re-export preferred routes to
778
	the instance. If <cf/in/ or <cf/out/ options are used, the
779
	command is restricted to one direction (re-import or
780
	re-export).
781

    
782
	This command is useful if appropriate filters have changed but
783
	the protocol instance was not restarted (or reloaded),
784
	therefore it still propagates the old set of routes. For example
785
	when <cf/configure soft/ command was used to change filters.
786

    
787
	Re-export always succeeds, but re-import is protocol-dependent
788
	and might fail (for example, if BGP neighbor does not support
789
	route-refresh extension). In that case, re-export is also
790
	skipped. Note that for the pipe protocol, both directions are
791
	always reloaded together (<cf/in/ or <cf/out/ options are
792
	ignored in that case).
793

    
794
	<tag/down/
795
	Shut BIRD down.
796

    
797
	<tag>debug <m/protocol/|<m/pattern/|all all|off|{ states | routes | filters | events | packets }</tag>
798
	Control protocol debugging.
799
</descrip>
800

    
801
<chapt>Filters
802

    
803
<sect>Introduction
804

    
805
<p>BIRD contains a simple programming language. (No, it can't yet read mail :-). There are
806
two objects in this language: filters and functions. Filters are interpreted by BIRD core when a route is
807
being passed between protocols and routing tables. The filter language contains control structures such
808
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>. 
809

    
810
<p>Filter gets the route, looks at its attributes and
811
modifies some of them if it wishes. At the end, it decides whether to
812
pass the changed route through (using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks
813
like this:
814

    
815
<code>
816
filter not_too_far
817
int var;
818
{
819
	if defined( rip_metric ) then
820
		var = rip_metric;
821
	else {
822
		var = 1;
823
		rip_metric = 1;
824
	}
825
	if rip_metric &gt; 10 then
826
		reject "RIP metric is too big";
827
	else
828
		accept "ok";
829
}
830
</code>
831

    
832
<p>As you can see, a filter has a header, a list of local variables, and a body. The header consists of
833
the <cf/filter/ keyword followed by a (unique) name of filter. The list of local variables consists of
834
<cf><M>type name</M>;</cf> pairs where each pair defines one local variable. The body consists of
835
<cf> { <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You can group
836
several statements to a single compound statement by using braces (<cf>{ <M>statements</M> }</cf>) which is useful if
837
you want to make a bigger block of code conditional.
838

    
839
<p>BIRD supports functions, so that you don't have to repeat the same blocks of code over and
840
over. Functions can have zero or more parameters and they can have local variables. Recursion is not allowed. Function definitions
841
look like this:
842

    
843
<code>
844
function name ()
845
int local_variable;
846
{
847
	local_variable = 5;
848
}
849

    
850
function with_parameters (int parameter)
851
{
852
	print parameter;
853
}
854
</code>
855

    
856
<p>Unlike in C, variables are declared after the <cf/function/ line, but before the first <cf/{/. You can't declare
857
variables in nested blocks. Functions are called like in C: <cf>name();
858
with_parameters(5);</cf>. Function may return values using the <cf>return <m/[expr]/</cf>
859
command. Returning a value exits from current function (this is similar to C).
860

    
861
<p>Filters are declared in a way similar to functions except they can't have explicit
862
parameters. They get a route table entry as an implicit parameter, it is also passed automatically 
863
to any functions called. The filter must terminate with either
864
<cf/accept/ or <cf/reject/ statement. If there's a runtime error in filter, the route
865
is rejected. 
866

    
867
<p>A nice trick to debug filters is to use <cf>show route filter
868
<m/name/</cf> from the command line client. An example session might look
869
like:
870

    
871
<code>
872
pavel@bug:~/bird$ ./birdc -s bird.ctl
873
BIRD 0.0.0 ready.
874
bird> show route
875
10.0.0.0/8         dev eth0 [direct1 23:21] (240)
876
195.113.30.2/32    dev tunl1 [direct1 23:21] (240)
877
127.0.0.0/8        dev lo [direct1 23:21] (240)
878
bird> show route ?
879
show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
880
bird> show route filter { if 127.0.0.5 &tilde; net then accept; }
881
127.0.0.0/8        dev lo [direct1 23:21] (240)
882
bird>
883
</code>
884

    
885
<sect>Data types
886

    
887
<p>Each variable and each value has certain type. Booleans, integers and enums are
888
incompatible with each other (that is to prevent you from shooting in the foot).
889

    
890
<descrip>
891
	<tag/bool/ This is a boolean type, it can have only two values, <cf/true/ and
892
	  <cf/false/. Boolean is the only type you can use in <cf/if/
893
	  statements.
894

    
895
	<tag/int/ This is a general integer type, you can expect it to store signed values from -2000000000
896
	  to +2000000000. Overflows are not checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
897

    
898
	<tag/pair/ This is a pair of two short integers. Each component can have values from 0 to
899
	  65535. Literals of this type are written as <cf/(1234,5678)/. The same syntax can also be
900
	  used to construct a pair from two arbitrary integer expressions (for example <cf/(1+2,a)/).
901

    
902
	<tag/quad/ This is a dotted quad of numbers used to represent
903
	  router IDs (and others).  Each component can have a value
904
	  from 0 to 255. Literals of this type are written like IPv4
905
	  addresses.
906

    
907
	<tag/string/ This is a string of characters. There are no ways to modify strings in
908
	  filters. You can pass them between functions, assign them to variables of type <cf/string/, print
909
	  such variables, but you can't concatenate two strings. String literals
910
	  are written as <cf/"This is a string constant"/.
911

    
912
	<tag/ip/ This type can hold a single IP address. Depending on the compile-time configuration of BIRD you are using, it
913
	  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>
914
	  on values of type ip. It masks out all but first <cf><M>num</M></cf> bits from the IP
915
	  address. So <cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
916

    
917
	<tag/prefix/ This type can hold a network prefix consisting of IP address and prefix length. Prefix literals are written as
918
	  <cf><M>ipaddress</M>/<M>pxlen</M></cf>, or
919
	  <cf><m>ipaddress</m>/<m>netmask</m></cf>. There are two special
920
	  operators on prefixes:
921
	  <cf/.ip/ which extracts the IP address from the pair, and <cf/.len/, which separates prefix
922
	  length from the pair. So <cf>1.2.0.0/16.pxlen = 16</cf> is true.
923

    
924
	<tag/ec/ This is a specialized type used to represent BGP
925
	  extended community values. It is essentially a 64bit value,
926
	  literals of this type are usually written as <cf>(<m/kind/,
927
	  <m/key/, <m/value/)</cf>, where <cf/kind/ is a kind of
928
	  extended community (e.g. <cf/rt/ / <cf/ro/ for a route
929
	  target / route origin communities), the format and possible
930
	  values of <cf/key/ and <cf/value/ are usually integers, but
931
	  it depends on the used kind. Similarly to pairs, ECs can be
932
	  constructed using expressions for <cf/key/ and
933
	  <cf/value/ parts, (e.g. <cf/(ro, myas, 3*10)/, where
934
	  <cf/myas/ is an integer variable).
935
 
936
	<tag/int|pair|quad|ip|prefix|ec|enum set/
937
	  Filters recognize four types of sets. Sets are similar to strings: you can pass them around
938
	  but you can't modify them. Literals of type <cf>int set</cf> look like <cf>
939
	  [ 1, 2, 5..7 ]</cf>. As you can see, both simple values and ranges are permitted in
940
	  sets.
941

    
942
	  For pair sets, expressions like <cf/(123,*)/ can be used to denote ranges (in
943
	  that case <cf/(123,0)..(123,65535)/). You can also use <cf/(123,5..100)/ for range
944
	  <cf/(123,5)..(123,100)/. You can also use <cf/*/ and <cf/a..b/ expressions
945
	  in the first part of a pair, note that such expressions are translated to a set
946
	  of intervals, which may be memory intensive. E.g. <cf/(*,4..20)/ is translated to
947
	  <cf/(0,4..20), (1,4..20), (2,4..20), ... (65535, 4..20)/.
948

    
949
	  EC sets use similar expressions like pair sets, e.g. <cf/(rt, 123, 10..20)/ 
950
	  or <cf/(ro, 123, *)/. Expressions requiring the translation (like  <cf/(rt, *, 3)/)
951
	  are not allowed (as they usually have 4B range for ASNs).
952

    
953
	  You can also use expressions for int, pair and EC set values. However it must
954
	  be possible to evaluate these expressions before daemon boots. So you can use
955
	  only constants inside them. E.g.
956
	<code>
957
	 define one=1;
958
	 define myas=64500;
959
	 int set odds;
960
	 pair set ps;
961
	 ec set es;
962

    
963
	 odds = [ one, 2+1, 6-one, 2*2*2-1, 9, 11 ];
964
	 ps = [ (1,one+one), (3,4)..(4,8), (5,*), (6,3..6), (7..9,*) ];
965
	 es = [ (rt, myas, 3*10), (rt, myas+one, 0..16*16*16-1), (ro, myas+2, *) ];
966
	</code>
967

    
968
	  Sets of prefixes are special: their literals does not allow ranges, but allows
969
	  prefix patterns that are written as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
970
	  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 
971
	  the first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are identical and <cf>len1 &lt;= ip1 &lt;= len2</cf>.
972
	  A valid prefix pattern has to satisfy <cf>low &lt;= high</cf>, but <cf/pxlen/ is not constrained by <cf/low/
973
	  or <cf/high/. Obviously, a prefix matches a prefix set literal if it matches any prefix pattern in the
974
	  prefix set literal.
975

    
976
	  There are also two shorthands for prefix patterns: <cf><m>address</m>/<m/len/+</cf> is a shorthand for
977
	  <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), 
978
	  that means network prefix <cf><m>address</m>/<m/len/</cf> and all its subnets. <cf><m>address</m>/<m/len/-</cf>
979
	  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>
980
	  and all its supernets (network prefixes that contain it).
981

    
982
	  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
983
	  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
984
	  <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
985
	  IP address) whose prefix length is 20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP address
986
	  <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 &tilde; [ 1.0.0.0/8{15,17} ]</cf> is true,
987
	  but <cf>1.0.0.0/16 &tilde; [ 1.0.0.0/8- ]</cf> is false.
988

    
989
	  Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
990
	  in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as 
991
	  <cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
992
	  <cf>192.168.0.0/16{24,32}</cf>.
993

    
994
	<tag/enum/
995
	  Enumeration types are fixed sets of possibilities. You can't define your own
996
	  variables of such type, but some route attributes are of enumeration
997
	  type. Enumeration types are incompatible with each other.
998

    
999
	<tag/bgppath/
1000
	  BGP path is a list of autonomous system numbers. You can't write literals of this type.
1001
	  There are several special operators on bgppaths:
1002

    
1003
	  <cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
1004

    
1005
          <cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
1006

    
1007
	  Both <cf/first/ and <cf/last/ return zero if there is no appropriate ASN,
1008
          for example if the path contains an AS set element as the first (or the last) part.
1009

    
1010
          <cf><m/P/.len</cf> returns the length of path <m/P/.
1011

    
1012
          <cf>prepend(<m/P/,<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and returns the result.
1013
          Statement <cf><m/P/ = prepend(<m/P/, <m/A/);</cf> can be shortened to
1014
          <cf><m/P/.prepend(<m/A/);</cf> if <m/P/ is appropriate route attribute
1015
          (for example <cf/bgp_path/).
1016

    
1017
	<tag/bgpmask/
1018
	  BGP masks are patterns used for BGP path matching
1019
	  (using <cf>path &tilde; [= 2 3 5 * =]</cf> syntax). The masks
1020
	  resemble wildcard patterns as used by UNIX shells. Autonomous
1021
	  system numbers match themselves, <cf/*/ matches any (even empty)
1022
	  sequence of arbitrary AS numbers and <cf/?/ matches one arbitrary AS number.
1023
	  For example, if <cf>bgp_path</cf> is 4 3 2 1, then:
1024
	  <tt>bgp_path &tilde; [= * 4 3 * =]</tt> is true, but 
1025
	  <tt>bgp_path &tilde; [= * 4 5 * =]</tt> is false.
1026
	  BGP mask expressions can also contain integer expressions enclosed in parenthesis
1027
	  and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>.
1028
	  There is also old syntax that uses / .. / instead of [= .. =] and ? instead of *.
1029

    
1030
	<tag/clist/
1031
	  Clist is similar to a set, except that unlike other sets, it
1032
	  can be modified. The type is used for community list (a set
1033
	  of pairs) and for cluster list (a set of quads). There exist
1034
	  no literals of this type. There are three special operators on
1035
	  clists:
1036

    
1037
          <cf>add(<m/C/,<m/P/)</cf> adds pair (or quad) <m/P/ to clist
1038
	  <m/C/ and returns the result.  If item <m/P/ is already in
1039
	  clist <m/C/, it does nothing. <m/P/ may also be a clist,
1040
	  in that case all its members are added; i.e., it works as clist union.
1041

    
1042
          <cf>delete(<m/C/,<m/P/)</cf> deletes pair (or quad)
1043
	  <m/P/ from clist <m/C/ and returns the result.  If clist
1044
	  <m/C/ does not contain item <m/P/, it does nothing.
1045
	  <m/P/ may also be a pair (or quad) set, in that case the
1046
	  operator deletes all items from clist <m/C/ that are also
1047
	  members of set <m/P/. Moreover, <m/P/ may also be a clist,
1048
	  which works analogously; i.e., it works as clist difference.
1049

    
1050
          <cf>filter(<m/C/,<m/P/)</cf> deletes all items from clist
1051
	  <m/C/ that are not members of pair (or quad) set <m/P/.
1052
	  I.e., <cf/filter/ do the same as <cf/delete/ with inverted
1053
	  set <m/P/. <m/P/ may also be a clist, which works analogously;
1054
	  i.e., it works as clist intersection.
1055

    
1056
          Statement <cf><m/C/ = add(<m/C/, <m/P/);</cf> can be shortened to
1057
          <cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route
1058
          attribute (for example <cf/bgp_community/). Similarly for
1059
          <cf/delete/ and <cf/filter/.
1060

    
1061
	<tag/eclist/
1062
	  Eclist is a data type used for BGP extended community lists.
1063
	  Eclists are very similar to clists, but they are sets of ECs
1064
	  instead of pairs. The same operations (like <cf/add/,
1065
	  <cf/delete/, or <cf/&tilde;/ membership operator) can be
1066
	  used to modify or test eclists, with ECs instead of pairs as
1067
	  arguments.
1068
</descrip>
1069

    
1070
<sect>Operators
1071

    
1072
<p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>, parentheses <cf/(a*(b+c))/, comparison
1073
<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;/). 
1074
Special operators include <cf/&tilde;/ for "is element of a set" operation - it can be
1075
used on element and set of elements of the same type (returning true if element is contained in the given set), or
1076
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
1077
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).
1078

    
1079
<p>There is one operator related to ROA infrastructure -
1080
<cf/roa_check()/. It examines a ROA table and does RFC 6483 route
1081
origin validation for a given network prefix. The basic usage
1082
is <cf>roa_check(<m/table/)</cf>, which checks current route (which
1083
should be from BGP to have AS_PATH argument) in the specified ROA
1084
table and returns ROA_UNKNOWN if there is no relevant ROA, ROA_VALID
1085
if there is a matching ROA, or ROA_INVALID if there are some relevant
1086
ROAs but none of them match. There is also an extended variant
1087
<cf>roa_check(<m/table/, <m/prefix/, <m/asn/)</cf>, which allows to
1088
specify a prefix and an ASN as arguments.
1089

    
1090

    
1091
<sect>Control structures
1092

    
1093
<p>Filters support two control structures: conditions and case switches. 
1094

    
1095
<p>Syntax of a condition is: <cf>if
1096
<M>boolean expression</M> then <M>command1</M>; else <M>command2</M>;</cf> and you can use <cf>{
1097
<M>command_1</M>; <M>command_2</M>; <M>...</M> }</cf> instead of either command. The <cf>else</cf>
1098
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.
1099

    
1100
<p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case <m/expr/ { else: |
1101
<m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [ ... ] }</cf>. The expression after
1102
<cf>case</cf> can be of any type which can be on the left side of the &tilde; operator and anything that could
1103
be a member of a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/ grouping.
1104
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.
1105

    
1106
<p>Here is example that uses <cf/if/ and <cf/case/ structures:
1107

    
1108
<code>
1109
case arg1 {
1110
	2: print "two"; print "I can do more commands without {}";
1111
	3 .. 5: print "three to five";
1112
	else: print "something else";
1113
}
1114

    
1115
if 1234 = i then printn "."; else { 
1116
  print "not 1234"; 
1117
  print "You need {} around multiple commands"; 
1118
}
1119
</code>
1120

    
1121
<sect>Route attributes
1122

    
1123
<p>A filter is implicitly passed a route, and it can access its
1124
attributes just like it accesses variables. Attempts to access undefined
1125
attribute result in a runtime error; you can check if an attribute is
1126
defined by using the <cf>defined( <m>attribute</m> )</cf> operator.
1127
One notable exception to this rule are attributes of clist type, where
1128
undefined value is regarded as empty clist for most purposes.
1129

    
1130
<descrip>
1131
	<tag><m/prefix/ net</tag>
1132
	Network the route is talking about. Read-only. (See the chapter about routing tables.)
1133

    
1134
	<tag><m/enum/ scope</tag>
1135
	The scope of the route. Possible values: <cf/SCOPE_HOST/ for
1136
	routes local to this host, <cf/SCOPE_LINK/ for those specific
1137
	for a physical link, <cf/SCOPE_SITE/ and
1138
	<cf/SCOPE_ORGANIZATION/ for private routes and
1139
	<cf/SCOPE_UNIVERSE/ for globally visible routes. This
1140
	attribute is not interpreted by BIRD and can be used to mark
1141
	routes in filters. The default value for new routes is
1142
	<cf/SCOPE_UNIVERSE/.
1143

    
1144
	<tag><m/int/ preference</tag>
1145
	Preference of the route. Valid values are 0-65535. (See the chapter about routing tables.)
1146

    
1147
	<tag><m/ip/ from</tag>
1148
	The router which the route has originated from. Read-only.
1149
	
1150
	<tag><m/ip/ gw</tag>
1151
	Next hop packets routed using this route should be forwarded to.
1152

    
1153
	<tag><m/string/ proto</tag>
1154
	The name of the protocol which the route has been imported from. Read-only.
1155

    
1156
	<tag><m/enum/ source</tag>
1157
	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/.
1158

    
1159
	<tag><m/enum/ cast</tag>
1160

    
1161
	Route type (Currently <cf/RTC_UNICAST/ for normal routes,
1162
	<cf/RTC_BROADCAST/, <cf/RTC_MULTICAST/, <cf/RTC_ANYCAST/ will
1163
	be used in the future for broadcast, multicast and anycast
1164
	routes). Read-only.
1165

    
1166
	<tag><m/enum/ dest</tag>
1167
	Type of destination the packets should be sent to
1168
	(<cf/RTD_ROUTER/ for forwarding to a neighboring router,
1169
	<cf/RTD_DEVICE/ for routing to a directly-connected network,
1170
	<cf/RTD_MULTIPATH/ for multipath destinations,
1171
	<cf/RTD_BLACKHOLE/ for packets to be silently discarded,
1172
	<cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that
1173
	should be returned with ICMP host unreachable / ICMP
1174
	administratively prohibited messages). Can be changed, but
1175
	only to <cf/RTD_BLACKHOLE/, <cf/RTD_UNREACHABLE/ or
1176
	<cf/RTD_PROHIBIT/.
1177

    
1178
	<tag><m/int/ igp_metric</tag>
1179
	The optional attribute that can be used to specify a distance
1180
	to the network for routes that do not have a native protocol
1181
	metric attribute (like <cf/ospf_metric1/ for OSPF routes). It
1182
	is used mainly by BGP to compare internal distances to boundary
1183
	routers (see below). It is also used when the route is exported
1184
	to OSPF as a default value for OSPF type 1 metric.
1185
</descrip>
1186

    
1187
<p>There also exist some protocol-specific attributes which are described in the corresponding protocol sections.
1188

    
1189
<sect>Other statements
1190

    
1191
<p>The following statements are available:
1192

    
1193
<descrip>
1194
	<tag><m/variable/ = <m/expr/</tag> Set variable to a given value.
1195

    
1196
	<tag>accept|reject [ <m/expr/ ]</tag> Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
1197

    
1198
	<tag>return <m/expr/</tag> Return <cf><m>expr</m></cf> from the current function, the function ends at this point.
1199

    
1200
	<tag>print|printn <m/expr/ [<m/, expr.../]</tag>
1201
	Prints given expressions; useful mainly while debugging
1202
	filters. The <cf/printn/ variant does not terminate the line.
1203

    
1204
	<tag>quitbird</tag>
1205
	Terminates BIRD. Useful when debugging the filter interpreter.
1206
</descrip>
1207

    
1208
<chapt>Protocols
1209

    
1210
<sect>BGP
1211

    
1212
<p>The Border Gateway Protocol is the routing protocol used for backbone
1213
level routing in the today's Internet. Contrary to the other protocols, its convergence
1214
doesn't rely on all routers following the same rules for route selection,
1215
making it possible to implement any routing policy at any router in the
1216
network, the only restriction being that if a router advertises a route,
1217
it must accept and forward packets according to it.
1218

    
1219
<p>BGP works in terms of autonomous systems (often abbreviated as
1220
AS). Each AS is a part of the network with common management and
1221
common routing policy. It is identified by a unique 16-bit number
1222
(ASN).  Routers within each AS usually exchange AS-internal routing
1223
information with each other using an interior gateway protocol (IGP,
1224
such as OSPF or RIP). Boundary routers at the border of
1225
the AS communicate global (inter-AS) network reachability information with
1226
their neighbors in the neighboring AS'es via exterior BGP (eBGP) and
1227
redistribute received information to other routers in the AS via
1228
interior BGP (iBGP).
1229

    
1230
<p>Each BGP router sends to its neighbors updates of the parts of its
1231
routing table it wishes to export along with complete path information
1232
(a list of AS'es the packet will travel through if it uses the particular
1233
route) in order to avoid routing loops.
1234

    
1235
<p>BIRD supports all requirements of the BGP4 standard as defined in
1236
RFC 4271<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4271.txt">
1237
It also supports the community attributes
1238
(RFC 1997<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1997.txt">),
1239
capability negotiation
1240
(RFC 3392<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc3392.txt">),
1241
MD5 password authentication
1242
(RFC 2385<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2385.txt">),
1243
extended communities
1244
(RFC 4360<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4360.txt">),
1245
route reflectors 
1246
(RFC 4456<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4456.txt">),
1247
multiprotocol extensions
1248
(RFC 4760<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4760.txt">),
1249
4B AS numbers 
1250
(RFC 4893<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4893.txt">),
1251
and 4B AS numbers in extended communities
1252
(RFC 5668<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc5668.txt">).
1253

    
1254

    
1255
For IPv6, it uses the standard multiprotocol extensions defined in
1256
RFC 2283<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2283.txt">
1257
including changes described in the
1258
latest draft<htmlurl url="ftp://ftp.rfc-editor.org/internet-drafts/draft-ietf-idr-bgp4-multiprotocol-v2-05.txt">
1259
and applied to IPv6 according to
1260
RFC 2545<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2545.txt">.
1261

    
1262
<sect1>Route selection rules
1263

    
1264
<p>BGP doesn't have any simple metric, so the rules for selection of an optimal
1265
route among multiple BGP routes with the same preference are a bit more complex
1266
and they are implemented according to the following algorithm. It starts the first
1267
rule, if there are more "best" routes, then it uses the second rule to choose
1268
among them and so on.
1269

    
1270
<itemize>
1271
	<item>Prefer route with the highest Local Preference attribute.
1272
	<item>Prefer route with the shortest AS path.
1273
	<item>Prefer IGP origin over EGP and EGP origin over incomplete.
1274
	<item>Prefer the lowest value of the Multiple Exit Discriminator.
1275
	<item>Prefer routes received via eBGP over ones received via iBGP.
1276
	<item>Prefer routes with lower internal distance to a boundary router.
1277
	<item>Prefer the route with the lowest value of router ID of the
1278
	advertising router.
1279
</itemize>
1280

    
1281
<sect1>IGP routing table
1282

    
1283
<p>BGP is mainly concerned with global network reachability and with
1284
routes to other autonomous systems. When such routes are redistributed
1285
to routers in the AS via BGP, they contain IP addresses of a boundary
1286
routers (in route attribute NEXT_HOP). BGP depends on existing IGP
1287
routing table with AS-internal routes to determine immediate next hops
1288
for routes and to know their internal distances to boundary routers
1289
for the purpose of BGP route selection. In BIRD, there is usually
1290
one routing table used for both IGP routes and BGP routes.
1291

    
1292
<sect1>Configuration
1293

    
1294
<p>Each instance of the BGP corresponds to one neighboring router.
1295
This allows to set routing policy and all the other parameters differently
1296
for each neighbor using the following configuration parameters:
1297

    
1298
<descrip>
1299
	<tag>local [<m/ip/] as <m/number/</tag> Define which AS we
1300
	are part of. (Note that contrary to other IP routers, BIRD is
1301
	able to act as a router located in multiple AS'es
1302
	simultaneously, but in such cases you need to tweak the BGP
1303
	paths manually in the filters to get consistent behavior.)
1304
	Optional <cf/ip/ argument specifies a source address,
1305
	equivalent to the <cf/source address/ option (see below).
1306
	This parameter is mandatory.
1307

    
1308
	<tag>neighbor <m/ip/ as <m/number/</tag> Define neighboring router
1309
	this instance will be talking to and what AS it's located in. Unless
1310
	you use the <cf/multihop/ clause, it must be directly connected to one
1311
	of your router's interfaces. In case the neighbor is in the same AS
1312
	as we are, we automatically switch to iBGP. This parameter is mandatory.
1313

    
1314
	<tag>multihop [<m/number/]</tag> Configure multihop BGP
1315
	session to a neighbor that isn't directly connected.
1316
	Accurately, this option should be used if the configured
1317
	neighbor IP address does not match with any local network
1318
	subnets. Such IP address have to be reachable through system
1319
	routing table. For multihop BGP it is recommended to
1320
	explicitly configure <cf/source address/ to have it
1321
	stable. Optional <cf/number/ argument can be used to specify
1322
	the number of hops (used for TTL). Note that the number of
1323
	networks (edges) in a path is counted, i.e. if two BGP
1324
	speakers are separated by one router, the number of hops is
1325
	2. Default: switched off.
1326

    
1327
	<tag>source address <m/ip/</tag> Define local address we
1328
	should use for next hop calculation and as a source address
1329
	for the BGP session. Default: the address of the local
1330
	end of the interface our neighbor is connected to.
1331

    
1332
	<tag>next hop self</tag> Avoid calculation of the Next Hop
1333
	attribute and always advertise our own source address as a
1334
	next hop.  This needs to be used only occasionally to
1335
	circumvent misconfigurations of other routers.  Default:
1336
	disabled.
1337

    
1338
	<tag>missing lladdr self|drop|ignore</tag>Next Hop attribute
1339
	in BGP-IPv6 sometimes contains just the global IPv6 address,
1340
	but sometimes it has to contain both global and link-local
1341
	IPv6 addresses. This option specifies what to do if BIRD have
1342
	to send both addresses but does not know link-local address.
1343
	This situation might happen when routes from other protocols
1344
	are exported to BGP, or when improper updates are received
1345
	from BGP peers.  <cf/self/ means that BIRD advertises its own
1346
	local address instead. <cf/drop/ means that BIRD skips that
1347
	prefixes and logs error. <cf/ignore/ means that BIRD ignores
1348
	the problem and sends just the global address (and therefore
1349
	forms improper BGP update). Default: <cf/self/, unless BIRD
1350
	is configured as a route server (option <cf/rs client/), in
1351
	that case default is <cf/ignore/, because route servers usually
1352
	do not forward packets themselves.
1353

    
1354
	<tag>gateway direct|recursive</tag>For received routes, their
1355
	<cf/gw/ (immediate next hop) attribute is computed from
1356
	received <cf/bgp_next_hop/ attribute. This option specifies
1357
	how it is computed. Direct mode means that the IP address from
1358
	<cf/bgp_next_hop/ is used if it is directly reachable,
1359
	otherwise the neighbor IP address is used. Recursive mode
1360
	means that the gateway is computed by an IGP routing table
1361
	lookup for the IP address from <cf/bgp_next_hop/. Recursive
1362
	mode is the behavior specified by the BGP standard. Direct
1363
	mode is simpler, does not require any routes in a routing
1364
	table, and was used in older versions of BIRD, but does not
1365
	handle well nontrivial iBGP setups and multihop.  Recursive
1366
	mode is incompatible with <ref id="dsc-sorted" name="sorted
1367
	tables">. Default: <cf/direct/ for singlehop eBGP,
1368
	<cf/recursive/ otherwise.
1369

    
1370
	<tag>igp table <m/name/</tag> Specifies a table that is used
1371
	as an IGP routing table. Default: the same as the table BGP is
1372
	connected to.
1373
	
1374
	<tag>ttl security <m/switch/</tag> Use GTSM (RFC 5082 - the
1375
	generalized TTL security mechanism). GTSM protects against
1376
	spoofed packets by ignoring received packets with a smaller
1377
	than expected TTL. To work properly, GTSM have to be enabled
1378
	on both sides of a BGP session. If both <cf/ttl security/ and
1379
	<cf/multihop/ options are enabled, <cf/multihop/ option should
1380
	specify proper hop value to compute expected TTL. Kernel
1381
	support required: Linux: 2.6.34+ (IPv4), 2.6.35+ (IPv6), BSD:
1382
	since long ago, IPv4 only. Note that full (ICMP protection,
1383
	for example) RFC 5082 support is provided by Linux
1384
	only. Default: disabled.
1385
	
1386
	<tag>password <m/string/</tag> Use this password for MD5 authentication
1387
	of BGP sessions. Default: no authentication. Password has to be set by
1388
	external utility (e.g. setkey(8)) on BSD systems.
1389

    
1390
	<tag>passive <m/switch/</tag> Standard BGP behavior is both
1391
        initiating outgoing connections and accepting incoming
1392
        connections. In passive mode, outgoing connections are not
1393
        initiated. Default: off.
1394

    
1395
	<tag>rr client</tag> Be a route reflector and treat the neighbor as
1396
	a route reflection client. Default: disabled.
1397

    
1398
	<tag>rr cluster id <m/IPv4 address/</tag> Route reflectors use cluster id
1399
	to avoid route reflection loops. When there is one route reflector in a cluster
1400
	it usually uses its router id as a cluster id, but when there are more route
1401
	reflectors in a cluster, these need to be configured (using this option) to
1402
	use a common cluster id. Clients in a cluster need not know their cluster
1403
	id and this option is not allowed for them. Default: the same as router id.
1404

    
1405
	<tag>rs client</tag> Be a route server and treat the neighbor
1406
	as a route server client. A route server is used as a
1407
	replacement for full mesh EBGP routing in Internet exchange
1408
	points in a similar way to route reflectors used in IBGP routing.
1409
	BIRD does not implement obsoleted RFC 1863, but uses ad-hoc implementation,
1410
	which behaves like plain EBGP but reduces modifications to advertised route
1411
	attributes to be transparent (for example does not prepend its AS number to
1412
	AS PATH attribute and keeps MED attribute). Default: disabled.
1413

    
1414
	<tag>secondary <m/switch/</tag> Usually, if an import filter
1415
	rejects a selected route, no other route is propagated for
1416
	that network. This option allows to try the next route in
1417
	order until one that is accepted is found or all routes for
1418
	that network are rejected. This can be used for route servers
1419
	that need to propagate different tables to each client but do
1420
	not want to have these tables explicitly (to conserve memory).
1421
	This option requires that the connected routing table is
1422
	<ref id="dsc-sorted" name="sorted">. Default: off.
1423

    
1424
	<tag>enable route refresh <m/switch/</tag> When BGP speaker
1425
	changes its import filter, it has to re-examine all routes
1426
	received from its neighbor against the new filter. As these
1427
	routes might not be available, there is a BGP protocol
1428
	extension Route Refresh (specified in RFC 2918) that allows
1429
	BGP speaker to request re-advertisement of all routes from its
1430
	neighbor. This option specifies whether BIRD advertises this
1431
	capability and accepts such requests. Even when disabled, BIRD
1432
	can send route refresh requests. Default: on.
1433

    
1434
	<tag>interpret communities <m/switch/</tag> RFC 1997 demands
1435
	that BGP speaker should process well-known communities like
1436
	no-export (65535, 65281) or no-advertise (65535, 65282). For
1437
	example, received route carrying a no-adverise community
1438
	should not be advertised to any of its neighbors. If this
1439
	option is enabled (which is by default), BIRD has such
1440
	behavior automatically (it is evaluated when a route is
1441
	exported to the BGP protocol just before the export filter).
1442
	Otherwise, this integrated processing of well-known
1443
	communities is disabled. In that case, similar behavior can be
1444
	implemented in the export filter.  Default: on.
1445

    
1446
	<tag>enable as4 <m/switch/</tag> BGP protocol was designed to use 2B AS numbers
1447
	and was extended later to allow 4B AS number. BIRD supports 4B AS extension,
1448
	but by disabling this option it can be persuaded not to advertise it and
1449
	to maintain old-style sessions with its neighbors. This might be useful for
1450
	circumventing bugs in neighbor's implementation of 4B AS extension.
1451
	Even when disabled (off), BIRD behaves internally as AS4-aware BGP router.
1452
	Default: on.
1453

    
1454
	<tag>capabilities <m/switch/</tag> Use capability advertisement
1455
	to advertise optional capabilities. This is standard behavior
1456
	for newer BGP implementations, but there might be some older
1457
	BGP implementations that reject such connection attempts.
1458
	When disabled (off), features that request it (4B AS support)
1459
	are also disabled. Default: on, with automatic fallback to
1460
	off when received capability-related error.
1461

    
1462
	<tag>advertise ipv4 <m/switch/</tag> Advertise IPv4 multiprotocol capability.
1463
	This is not a correct behavior according to the strict interpretation
1464
	of RFC 4760, but it is widespread and required by some BGP
1465
	implementations (Cisco and Quagga). This option is relevant
1466
	to IPv4 mode with enabled capability advertisement only. Default: on.
1467

    
1468
	<tag>route limit <m/number/</tag> The maximal number of routes
1469
	that may be imported from the protocol. If the route limit is
1470
	exceeded, the connection is closed with error. Limit is currently implemented as
1471
	<cf/import limit number exceed restart/. Default: no limit.
1472

    
1473
	<tag>disable after error <m/switch/</tag> When an error is encountered (either
1474
	locally or by the other side), disable the instance automatically
1475
	and wait for an administrator to fix the problem manually. Default: off.
1476

    
1477
	<tag>hold time <m/number/</tag> Time in seconds to wait for a Keepalive
1478
	message from the other side before considering the connection stale.
1479
	Default: depends on agreement with the neighboring router, we prefer
1480
	240 seconds if the other side is willing to accept it.
1481

    
1482
	<tag>startup hold time <m/number/</tag> Value of the hold timer used
1483
	before the routers have a chance to exchange open messages and agree
1484
	on the real value. Default: 240 seconds.
1485

    
1486
	<tag>keepalive time <m/number/</tag> Delay in seconds between sending
1487
	of two consecutive Keepalive messages. Default: One third of the hold time.
1488

    
1489
	<tag>connect retry time <m/number/</tag> Time in seconds to wait before
1490
	retrying a failed attempt to connect. Default: 120 seconds.
1491

    
1492
	<tag>start delay time <m/number/</tag> Delay in seconds between protocol
1493
	startup and the first attempt to connect. Default: 5 seconds.
1494

    
1495
	<tag>error wait time <m/number/,<m/number/</tag> Minimum and maximum delay in seconds between a protocol
1496
	failure (either local or reported by the peer) and automatic restart.
1497
	Doesn't apply when <cf/disable after error/ is configured. If consecutive
1498
	errors happen, the delay is increased exponentially until it reaches the maximum. Default: 60, 300.
1499

    
1500
	<tag>error forget time <m/number/</tag> Maximum time in seconds between two protocol
1501
	failures to treat them as a error sequence which makes the <cf/error wait time/
1502
	increase exponentially. Default: 300 seconds.
1503

    
1504
	<tag>path metric <m/switch/</tag> Enable comparison of path lengths
1505
	when deciding which BGP route is the best one. Default: on.
1506

    
1507
	<tag>med metric <m/switch/</tag> Enable comparison of MED
1508
	attributes (during best route selection) even between routes
1509
	received from different ASes.  This may be useful if all MED
1510
	attributes contain some consistent metric, perhaps enforced in
1511
	import filters of AS boundary routers. If this option is
1512
	disabled, MED attributes are compared only if routes are
1513
	received from the same AS (which is the standard behavior).
1514
	Default: off.
1515

    
1516
	<tag>deterministic med <m/switch/</tag> BGP route selection
1517
	algorithm is often viewed as a comparison between individual
1518
	routes (e.g. if a new route appears and is better than the
1519
	current best one, it is chosen as the new best one). But the
1520
	proper route selection, as specified by RFC 4271, cannot be
1521
	fully implemented in that way. The problem is mainly in
1522
	handling the MED attribute. BIRD, by default, uses an
1523
	simplification based on individual route comparison, which in
1524
	some cases may lead to temporally dependent behavior (i.e. the
1525
	selection is dependent on the order in which routes appeared).
1526
	This option enables a different (and slower) algorithm
1527
	implementing proper RFC 4271 route selection, which is
1528
	deterministic. Alternative way how to get deterministic
1529
	behavior is to use <cf/med metric/ option. This option is
1530
	incompatible with <ref id="dsc-sorted" name="sorted tables">.
1531
	Default: off.
1532

    
1533
	<tag>igp metric <m/switch/</tag> Enable comparison of internal
1534
 	distances to boundary routers during best route selection. Default: on.
1535

    
1536
	<tag>prefer older <m/switch/</tag> Standard route selection algorithm
1537
	breaks ties by comparing router IDs. This changes the behavior
1538
	to prefer older routes (when both are external and from different
1539
	peer). For details, see RFC 5004. Default: off.
1540

    
1541
	<tag>default bgp_med <m/number/</tag> Value of the Multiple Exit
1542
	Discriminator to be used during route selection when the MED attribute
1543
	is missing. Default: 0.
1544

    
1545
	<tag>default bgp_local_pref <m/number/</tag> A default value
1546
	for the Local Preference attribute. It is used when a new
1547
	Local Preference attribute is attached to a route by the BGP
1548
	protocol itself (for example, if a route is received through
1549
	eBGP and therefore does not have such attribute). Default: 100
1550
	(0 in pre-1.2.0 versions of BIRD).
1551
</descrip>
1552

    
1553
<sect1>Attributes
1554

    
1555
<p>BGP defines several route attributes. Some of them (those marked with `<tt/I/' in the
1556
table below) are available on internal BGP connections only, some of them (marked
1557
with `<tt/O/') are optional.
1558

    
1559
<descrip>
1560
	<tag>bgppath <cf/bgp_path/</tag> Sequence of AS numbers describing the AS path
1561
	the packet will travel through when forwarded according to the particular route.
1562
	In case of internal BGP it doesn't contain the number of the local AS.
1563

    
1564
	<tag>int <cf/bgp_local_pref/ [I]</tag> Local preference value used for
1565
	selection among multiple BGP routes (see the selection rules above). It's
1566
	used as an additional metric which is propagated through the whole local AS.
1567

    
1568
	<tag>int <cf/bgp_med/ [O]</tag> The Multiple Exit Discriminator of the route
1569
	is an optional attribute which is used on external (inter-AS) links to
1570
	convey to an adjacent AS the optimal entry point into the local AS.
1571
	The received attribute is also propagated over internal BGP links.
1572
	The attribute value is zeroed when a route is exported to an external BGP
1573
	instance to ensure that the attribute received from a neighboring AS is
1574
	not propagated to other neighboring ASes. A new value might be set in
1575
	the export filter of an external BGP instance.
1576
	See RFC 4451<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4451.txt">
1577
	for further discussion of BGP MED attribute.
1578

    
1579
	<tag>enum <cf/bgp_origin/</tag> Origin of the route: either <cf/ORIGIN_IGP/
1580
	if the route has originated in an interior routing protocol or
1581
	<cf/ORIGIN_EGP/ if it's been imported from the <tt>EGP</tt> protocol
1582
	(nowadays it seems to be obsolete) or <cf/ORIGIN_INCOMPLETE/ if the origin
1583
	is unknown.
1584

    
1585
	<tag>ip <cf/bgp_next_hop/</tag> Next hop to be used for forwarding of packets
1586
	to this destination. On internal BGP connections, it's an address of the
1587
	originating router if it's inside the local AS or a boundary router the
1588
	packet will leave the AS through if it's an exterior route, so each BGP
1589
	speaker within the AS has a chance to use the shortest interior path
1590
	possible to this point.
1591

    
1592
	<tag>void <cf/bgp_atomic_aggr/ [O]</tag> This is an optional attribute
1593
	which carries no value, but the sole presence of which indicates that the route
1594
	has been aggregated from multiple routes by some router on the path from
1595
	the originator.
1596

    
1597
<!-- we don't handle aggregators right since they are of a very obscure type
1598
	<tag>bgp_aggregator</tag>
1599
-->
1600
	<tag>clist <cf/bgp_community/ [O]</tag> List of community values associated
1601
	with the route. Each such value is a pair (represented as a <cf/pair/ data
1602
	type inside the filters) of 16-bit integers, the first of them containing the number of the AS which defines
1603
	the community and the second one being a per-AS identifier. There are lots
1604
	of uses of the community mechanism, but generally they are used to carry
1605
	policy information like "don't export to USA peers". As each AS can define
1606
	its own routing policy, it also has a complete freedom about which community
1607
	attributes it defines and what will their semantics be.
1608

    
1609
	<tag>eclist <cf/bgp_ext_community/ [O]</tag> List of extended community
1610
	values associated with the route. Extended communities have similar usage
1611
	as plain communities, but they have an extended range (to allow 4B ASNs)
1612
	and a nontrivial structure with a type field. Individual community values are
1613
	represented using an <cf/ec/ data type inside the filters.
1614

    
1615
	<tag>quad <cf/bgp_originator_id/ [I, O]</tag> This attribute is created by the
1616
	route reflector when reflecting the route and contains the router ID of the
1617
	originator of the route in the local AS.
1618

    
1619
	<tag>clist <cf/bgp_cluster_list/ [I, O]</tag> This attribute contains a list
1620
	of cluster IDs of route reflectors. Each route reflector prepends its
1621
	cluster ID when reflecting the route.
1622
</descrip>
1623

    
1624
<sect1>Example
1625

    
1626
<p><code>
1627
protocol bgp {
1628
	local as 65000;			     # Use a private AS number
1629
	neighbor 198.51.100.130 as 64496;    # Our neighbor ...
1630
	multihop;			     # ... which is connected indirectly
1631
	export filter {			     # We use non-trivial export rules
1632
		if source = RTS_STATIC then { # Export only static routes
1633
		        # Assign our community
1634
			bgp_community.add((65000,64501));
1635
			# Artificially increase path length
1636
			# by advertising local AS number twice
1637
			if bgp_path ~ [= 65000 =] then
1638
				bgp_path.prepend(65000);
1639
			accept;
1640
		}
1641
		reject;
1642
	};
1643
	import all;
1644
	source address 198.51.100.14;	# Use a non-standard source address
1645
}
1646
</code>
1647

    
1648
<sect>Device
1649

    
1650
<p>The Device protocol is not a real routing protocol.  It doesn't generate
1651
any routes and it only serves as a module for getting information about network
1652
interfaces from the kernel.
1653

    
1654
<p>Except for very unusual circumstances, you probably should include
1655
this protocol in the configuration since almost all other protocols
1656
require network interfaces to be defined for them to work with.
1657

    
1658
<sect1>Configuration
1659

    
1660
<p><descrip>
1661
	<tag>scan time <m/number/</tag> Time in seconds between two scans
1662
	of the network interface list. On systems where we are notified about
1663
	interface status changes asynchronously (such as newer versions of
1664
	Linux), we need to scan the list only in order to avoid confusion by lost
1665
	notification messages, so the default time is set to a large value.
1666

    
1667
	<tag>primary  [ "<m/mask/" ] <m/prefix/</tag>
1668
	If a network interface has more than one network address, BIRD
1669
	has to choose one of them as a primary one. By default, BIRD
1670
	chooses the lexicographically smallest address as the primary
1671
	one.
1672

    
1673
	This option allows to specify which network address should be
1674
	chosen as a primary one. Network addresses that match
1675
	<m/prefix/ are preferred to non-matching addresses. If more
1676
	<cf/primary/ options are used, the first one has the highest
1677
	preference. If "<m/mask/" is specified, then such
1678
	<cf/primary/ option is relevant only to matching network
1679
	interfaces.
1680

    
1681
	In all cases, an address marked by operating system as
1682
	secondary cannot be chosen as the primary one. 
1683
</descrip>
1684

    
1685
<p>As the Device protocol doesn't generate any routes, it cannot have
1686
any attributes. Example configuration looks like this:
1687

    
1688
<p><code>
1689
protocol device {
1690
	scan time 10;		# Scan the interfaces often
1691
	primary "eth0" 192.168.1.1;
1692
	primary 192.168.0.0/16;
1693
}
1694
</code>
1695

    
1696
<sect>Direct
1697

    
1698
<p>The Direct protocol is a simple generator of device routes for all the
1699
directly connected networks according to the list of interfaces provided
1700
by the kernel via the Device protocol.
1701

    
1702
<p>The question is whether it is a good idea to have such device
1703
routes in BIRD routing table. OS kernel usually handles device routes
1704
for directly connected networks by itself so we don't need (and don't
1705
want) to export these routes to the kernel protocol. OSPF protocol
1706
creates device routes for its interfaces itself and BGP protocol is
1707
usually used for exporting aggregate routes. Although there are some
1708
use cases that use the direct protocol (like abusing eBGP as an IGP
1709
routing protocol), in most cases it is not needed to have these device
1710
routes in BIRD routing table and to use the direct protocol.
1711

    
1712
<p>There is one notable case when you definitely want to use the
1713
direct protocol -- running BIRD on BSD systems. Having high priority
1714
device routes for directly connected networks from the direct protocol
1715
protects kernel device routes from being overwritten or removed by IGP
1716
routes during some transient network conditions, because a lower
1717
priority IGP route for the same network is not exported to the kernel
1718
routing table. This is an issue on BSD systems only, as on Linux
1719
systems BIRD cannot change non-BIRD route in the kernel routing table.
1720

    
1721
<p>The only configurable thing about direct is what interfaces it watches:
1722

    
1723
<p><descrip>
1724
	<tag>interface <m/pattern [, ...]/</tag> By default, the Direct
1725
	protocol will generate device routes for all the interfaces
1726
	available. If you want to restrict it to some subset of interfaces
1727
	(for example if you're using multiple routing tables for policy
1728
	routing and some of the policy domains don't contain all interfaces),
1729
	just use this clause.
1730
</descrip>
1731

    
1732
<p>Direct device routes don't contain any specific attributes.
1733

    
1734
<p>Example config might look like this:
1735

    
1736
<p><code>
1737
protocol direct {
1738
	interface "-arc*", "*";		# Exclude the ARCnets
1739
}
1740
</code>
1741

    
1742
<sect>Kernel
1743

    
1744
<p>The Kernel protocol is not a real routing protocol. Instead of communicating
1745
with other routers in the network, it performs synchronization of BIRD's routing
1746
tables with the OS kernel. Basically, it sends all routing table updates to the kernel
1747
and from time to time it scans the kernel tables to see whether some routes have
1748
disappeared (for example due to unnoticed up/down transition of an interface)
1749
or whether an `alien' route has been added by someone else (depending on the
1750
<cf/learn/ switch, such routes are either ignored or accepted to our
1751
table).
1752

    
1753
<p>Unfortunately, there is one thing that makes the routing table
1754
synchronization a bit more complicated. In the kernel routing table
1755
there are also device routes for directly connected networks. These
1756
routes are usually managed by OS itself (as a part of IP address
1757
configuration) and we don't want to touch that.  They are completely
1758
ignored during the scan of the kernel tables and also the export of
1759
device routes from BIRD tables to kernel routing tables is restricted
1760
to prevent accidental interference. This restriction can be disabled using
1761
<cf/device routes/ switch.
1762

    
1763
<p>If your OS supports only a single routing table, you can configure
1764
only one instance of the Kernel protocol. If it supports multiple
1765
tables (in order to allow policy routing; such an OS is for example
1766
Linux), you can run as many instances as you want, but each of them
1767
must be connected to a different BIRD routing table and to a different
1768
kernel table.
1769

    
1770
<p>Because the kernel protocol is partially integrated with the
1771
connected routing table, there are two limitations - it is not
1772
possible to connect more kernel protocols to the same routing table
1773
and changing route destination/gateway in an export
1774
filter of a kernel protocol does not work. Both limitations can be
1775
overcome using another routing table and the pipe protocol.
1776

    
1777
<sect1>Configuration
1778

    
1779
<p><descrip>
1780
	<tag>persist <m/switch/</tag> Tell BIRD to leave all its routes in the
1781
	routing tables when it exits (instead of cleaning them up).
1782
	<tag>scan time <m/number/</tag> Time in seconds between two consecutive scans of the
1783
	kernel routing table.
1784
	<tag>learn <m/switch/</tag> Enable learning of routes added to the kernel
1785
	routing tables by other routing daemons or by the system administrator.
1786
	This is possible only on systems which support identification of route
1787
	authorship.
1788

    
1789
	<tag>device routes <m/switch/</tag> Enable export of device
1790
	routes to the kernel routing table. By default, such routes
1791
	are rejected (with the exception of explicitly configured
1792
	device routes from the static protocol) regardless of the
1793
	export filter to protect device routes in kernel routing table
1794
	(managed by OS itself) from accidental overwriting or erasing.
1795

    
1796
	<tag>kernel table <m/number/</tag> Select which kernel table should
1797
	this particular instance of the Kernel protocol work with. Available
1798
	only on systems supporting multiple routing tables.
1799
</descrip>
1800

    
1801
<sect1>Attributes
1802

    
1803
<p>The Kernel protocol defines several attributes. These attributes
1804
are translated to appropriate system (and OS-specific) route attributes.
1805
We support these attributes:
1806

    
1807
<descrip>
1808
	<tag>int <cf/krt_source/</tag> The original source of the imported
1809
	kernel route.  The value is system-dependent. On Linux, it is
1810
	a value of the protocol field of the route. See
1811
	/etc/iproute2/rt_protos for common values.  On BSD, it is
1812
	based on STATIC and PROTOx flags. The attribute is read-only.
1813

    
1814
	<tag>int <cf/krt_metric/</tag> The kernel metric of
1815
	the route.  When multiple same routes are in a kernel routing
1816
	table, the Linux kernel chooses one with lower metric.
1817

    
1818
	<tag>ip <cf/krt_prefsrc/</tag> (Linux) The preferred source address.
1819
 	Used in source address selection for outgoing packets. Have to
1820
 	be one of IP addresses of the router.
1821

    
1822
	<tag>int <cf/krt_realm/</tag> (Linux) The realm of the route. Can be
1823
	used for traffic classification.
1824
</descrip>
1825

    
1826
<sect1>Example
1827

    
1828
<p>A simple configuration can look this way:
1829

    
1830
<p><code>
1831
protocol kernel {
1832
	export all;
1833
}
1834
</code>
1835

    
1836
<p>Or for a system with two routing tables:
1837

    
1838
<p><code>
1839
protocol kernel {		# Primary routing table
1840
	learn;			# Learn alien routes from the kernel
1841
	persist;		# Don't remove routes on bird shutdown
1842
	scan time 10;		# Scan kernel routing table every 10 seconds
1843
	import all;
1844
	export all;
1845
}
1846

    
1847
protocol kernel {		# Secondary routing table
1848
	table auxtable;
1849
	kernel table 100;
1850
	export all;
1851
}
1852
</code>
1853

    
1854
<sect>OSPF
1855

    
1856
<sect1>Introduction
1857

    
1858
<p>Open Shortest Path First (OSPF) is a quite complex interior gateway
1859
protocol. The current IPv4 version (OSPFv2) is defined in RFC
1860
2328<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2328.txt"> and
1861
the current IPv6 version (OSPFv3) is defined in RFC 5340<htmlurl
1862
url="ftp://ftp.rfc-editor.org/in-notes/rfc5340.txt">  It's a link state
1863
(a.k.a. shortest path first) protocol -- each router maintains a
1864
database describing the autonomous system's topology. Each participating
1865
router has an identical copy of the database and all routers run the
1866
same algorithm calculating a shortest path tree with themselves as a
1867
root. OSPF chooses the least cost path as the best path.
1868

    
1869
<p>In OSPF, the autonomous system can be split to several areas in order
1870
to reduce the amount of resources consumed for exchanging the routing
1871
information and to protect the other areas from incorrect routing data.
1872
Topology of the area is hidden to the rest of the autonomous system.
1873

    
1874
<p>Another very important feature of OSPF is that
1875
it can keep routing information from other protocols (like Static or BGP)
1876
in its link state database as external routes. Each external route can
1877
be tagged by the advertising router, making it possible to pass additional
1878
information between routers on the boundary of the autonomous system.
1879

    
1880
<p>OSPF quickly detects topological changes in the autonomous system (such
1881
as router interface failures) and calculates new loop-free routes after a short
1882
period of convergence. Only a minimal amount of 
1883
routing traffic is involved.
1884

    
1885
<p>Each router participating in OSPF routing periodically sends Hello messages
1886
to all its interfaces. This allows neighbors to be discovered dynamically.
1887
Then the neighbors exchange theirs parts of the link state database and keep it
1888
identical by flooding updates. The flooding process is reliable and ensures
1889
that each router detects all changes.
1890

    
1891
<sect1>Configuration
1892

    
1893
<p>In the main part of configuration, there can be multiple definitions of
1894
OSPF areas, each with a different id. These definitions includes many other
1895
switches and multiple definitions of interfaces. Definition of interface
1896
may contain many switches and constant definitions and list of neighbors
1897
on nonbroadcast networks.
1898

    
1899
<code>
1900
protocol ospf &lt;name&gt; {
1901
	rfc1583compat &lt;switch&gt;;
1902
	tick &lt;num&gt;;
1903
	ecmp &lt;switch&gt; [limit &lt;num&gt;];
1904
	area &lt;id&gt; {
1905
		stub;
1906
		nssa;
1907
		summary &lt;switch&gt;;
1908
		default nssa &lt;switch&gt;;
1909
		default cost &lt;num&gt;;
1910
		default cost2 &lt;num&gt;;
1911
		translator &lt;switch&gt;;
1912
		translator stability &lt;num&gt;;
1913

    
1914
                networks {
1915
			&lt;prefix&gt;;
1916
			&lt;prefix&gt; hidden;
1917
		}
1918
                external {
1919
			&lt;prefix&gt;;
1920
			&lt;prefix&gt; hidden;
1921
			&lt;prefix&gt; tag &lt;num&gt;;
1922
		}
1923
		stubnet &lt;prefix&gt;;
1924
		stubnet &lt;prefix&gt; {
1925
			hidden &lt;switch&gt;;
1926
			summary &lt;switch&gt;;
1927
			cost &lt;num&gt;;
1928
		}
1929
		interface &lt;interface pattern&gt; [instance &lt;num&gt;] {
1930
			cost &lt;num&gt;;
1931
			stub &lt;switch&gt;;
1932
			hello &lt;num&gt;;
1933
			poll &lt;num&gt;;
1934
			retransmit &lt;num&gt;;
1935
			priority &lt;num&gt;;
1936
			wait &lt;num&gt;;
1937
			dead count &lt;num&gt;;
1938
			dead &lt;num&gt;;
1939
			rx buffer [normal|large|&lt;num&gt;];
1940
			type [broadcast|bcast|pointopoint|ptp|
1941
				nonbroadcast|nbma|pointomultipoint|ptmp];
1942
			strict nonbroadcast &lt;switch&gt;;
1943
			real broadcast &lt;switch&gt;;
1944
			check link &lt;switch&gt;;
1945
			ecmp weight &lt;num&gt;;
1946
			authentication [none|simple|cryptographic];
1947
			password "&lt;text&gt;";
1948
			password "&lt;text&gt;" {
1949
				id &lt;num&gt;;
1950
				generate from "&lt;date&gt;";
1951
				generate to "&lt;date&gt;";
1952
				accept from "&lt;date&gt;";
1953
				accept to "&lt;date&gt;";
1954
			};
1955
			neighbors {
1956
				&lt;ip&gt;;
1957
				&lt;ip&gt; eligible;
1958
			};
1959
		};
1960
		virtual link &lt;id&gt; [instance &lt;num&gt;] {
1961
			hello &lt;num&gt;;
1962
			retransmit &lt;num&gt;;
1963
			wait &lt;num&gt;;
1964
			dead count &lt;num&gt;;
1965
			dead &lt;num&gt;;
1966
			authentication [none|simple|cryptographic];
1967
			password "&lt;text&gt;";
1968
		};
1969
	};
1970
}
1971
</code>
1972

    
1973
<descrip>
1974
	<tag>rfc1583compat <M>switch</M></tag>
1975
	 This option controls compatibility of routing table
1976
	 calculation with RFC 1583<htmlurl
1977
	 url="ftp://ftp.rfc-editor.org/in-notes/rfc1583.txt">. Default
1978
	 value is no.
1979

    
1980
	<tag>tick <M>num</M></tag>
1981
	 The routing table calculation and clean-up of areas' databases
1982
         is not performed when a single link state
1983
	 change arrives. To lower the CPU utilization, it's processed later
1984
	 at periodical intervals of <m/num/ seconds. The default value is 1.
1985

    
1986
	<tag>ecmp <M>switch</M> [limit <M>number</M>]</tag>
1987
	 This option specifies whether OSPF is allowed to generate
1988
	 ECMP (equal-cost multipath) routes. Such routes are used when
1989
	 there are several directions to the destination, each with
1990
	 the same (computed) cost. This option also allows to specify
1991
	 a limit on maximal number of nexthops in one route. By
1992
	 default, ECMP is disabled.  If enabled, default value of the
1993
	 limit is 16.
1994

    
1995
	<tag>area <M>id</M></tag>
1996
	 This defines an OSPF area with given area ID (an integer or an IPv4
1997
	 address, similarly to a router ID). The most important area is
1998
	 the backbone (ID 0) to which every other area must be connected.
1999

    
2000
	<tag>stub</tag>
2001
	 This option configures the area to be a stub area. External
2002
	 routes are not flooded into stub areas. Also summary LSAs can be
2003
	 limited in stub areas (see option <cf/summary/).
2004
	 By default, the area is not a stub area.
2005

    
2006
	<tag>nssa</tag>
2007
	 This option configures the area to be a NSSA (Not-So-Stubby
2008
	 Area). NSSA is a variant of a stub area which allows a
2009
	 limited way of external route propagation. Global external
2010
	 routes are not propagated into a NSSA, but an external route
2011
	 can be imported into NSSA as a (area-wide) NSSA-LSA (and
2012
	 possibly translated and/or aggregated on area boundary).
2013
	 By default, the area is not NSSA.
2014

    
2015
	<tag>summary <M>switch</M></tag>
2016
	 This option controls propagation of summary LSAs into stub or
2017
	 NSSA areas. If enabled, summary LSAs are propagated as usual,
2018
	 otherwise just the default summary route (0.0.0.0/0) is
2019
	 propagated (this is sometimes called totally stubby area). If
2020
	 a stub area has more area boundary routers, propagating
2021
	 summary LSAs could lead to more efficient routing at the cost
2022
	 of larger link state database. Default value is no.
2023

    
2024
	<tag>default nssa <M>switch</M></tag>
2025
 	 When <cf/summary/ option is enabled, default summary route is
2026
	 no longer propagated to the NSSA. In that case, this option
2027
	 allows to originate default route as NSSA-LSA to the NSSA.
2028
	 Default value is no.
2029

    
2030
	<tag>default cost <M>num</M></tag>
2031
	 This option controls the cost of a default route propagated to
2032
	 stub and NSSA areas. Default value is 1000.
2033

    
2034
	<tag>default cost2 <M>num</M></tag>
2035
	 When a default route is originated as NSSA-LSA, its cost
2036
	 can use either type 1 or type 2 metric. This option allows
2037
	 to specify the cost of a default route in type 2 metric.
2038
	 By default, type 1 metric (option <cf/default cost/) is used.
2039

    
2040
	<tag>translator <M>switch</M></tag>
2041
	 This option controls translation of NSSA-LSAs into external
2042
	 LSAs. By default, one translator per NSSA is automatically
2043
	 elected from area boundary routers. If enabled, this area
2044
	 boundary router would unconditionally translate all NSSA-LSAs
2045
	 regardless of translator election. Default value is no.
2046

    
2047
	<tag>translator stability <M>num</M></tag>
2048
	 This option controls the translator stability interval (in
2049
	 seconds). When the new translator is elected, the old one
2050
	 keeps translating until the interval is over. Default value
2051
	 is 40.
2052

    
2053
	<tag>networks { <m/set/ }</tag>
2054
         Definition of area IP ranges. This is used in summary LSA origination.
2055
	 Hidden networks are not propagated into other areas.
2056

    
2057
	<tag>external { <m/set/ }</tag>
2058
         Definition of external area IP ranges for NSSAs. This is used
2059
	 for NSSA-LSA translation. Hidden networks are not translated
2060
	 into external LSAs. Networks can have configured route tag.
2061

    
2062
	<tag>stubnet <m/prefix/ { <m/options/ }</tag>
2063
	 Stub networks are networks that are not transit networks
2064
	 between OSPF routers. They are also propagated through an
2065
	 OSPF area as a part of a link state database. By default,
2066
	 BIRD generates a stub network record for each primary network
2067
	 address on each OSPF interface that does not have any OSPF
2068
	 neighbors, and also for each non-primary network address on
2069
	 each OSPF interface. This option allows to alter a set of
2070
	 stub networks propagated by this router. 
2071

    
2072
	 Each instance of this option adds a stub network with given
2073
	 network prefix to the set of propagated stub network, unless
2074
	 option <cf/hidden/ is used. It also suppresses default stub
2075
	 networks for given network prefix. When option
2076
	 <cf/summary/ is used, also default stub networks that are
2077
	 subnetworks of given stub network are suppressed. This might
2078
	 be used, for example, to aggregate generated stub networks.
2079
	 
2080
	<tag>interface <M>pattern</M> [instance <m/num/]</tag>
2081
	 Defines that the specified interfaces belong to the area being defined.
2082
	 See <ref id="dsc-iface" name="interface"> common option for detailed description.
2083
	 In OSPFv3, you can specify instance ID for that interface
2084
	 description, so it is possible to have several instances of
2085
	 that interface with different options or even in different areas.
2086

    
2087
	<tag>virtual link <M>id</M> [instance <m/num/]</tag>
2088
	 Virtual link to router with the router id. Virtual link acts
2089
         as a point-to-point interface belonging to backbone. The
2090
         actual area is used as transport area. This item cannot be in
2091
         the backbone. In OSPFv3, you could also use several virtual
2092
         links to one destination with different instance IDs.
2093

    
2094
	<tag>cost <M>num</M></tag>
2095
	 Specifies output cost (metric) of an interface. Default value is 10.
2096

    
2097
	<tag>stub <M>switch</M></tag>
2098
	 If set to interface it does not listen to any packet and does not send
2099
	 any hello. Default value is no.
2100

    
2101
	<tag>hello <M>num</M></tag>
2102
	 Specifies interval in seconds between sending of Hello messages. Beware, all
2103
	 routers on the same network need to have the same hello interval.
2104
	 Default value is 10.
2105

    
2106
	<tag>poll <M>num</M></tag>
2107
	 Specifies interval in seconds between sending of Hello messages for
2108
	 some neighbors on NBMA network. Default value is 20.
2109

    
2110
	<tag>retransmit <M>num</M></tag>
2111
	 Specifies interval in seconds between retransmissions of unacknowledged updates.
2112
	 Default value is 5.
2113

    
2114
        <tag>priority <M>num</M></tag>
2115
	 On every multiple access network (e.g., the Ethernet) Designed Router
2116
	 and Backup Designed router are elected. These routers have some
2117
	 special functions in the flooding process. Higher priority increases
2118
	 preferences in this election. Routers with priority 0 are not
2119
	 eligible. Default value is 1.
2120

    
2121
	<tag>wait <M>num</M></tag>
2122
	 After start, router waits for the specified number of seconds between starting
2123
	 election and building adjacency. Default value is 40.
2124
	 
2125
	<tag>dead count <M>num</M></tag>
2126
	 When the router does not receive any messages from a neighbor in
2127
	 <m/dead count/*<m/hello/ seconds, it will consider the neighbor down.
2128

    
2129
	<tag>dead <M>num</M></tag>
2130
	 When the router does not receive any messages from a neighbor in
2131
	 <m/dead/ seconds, it will consider the neighbor down. If both directives
2132
	 <m/dead count/ and <m/dead/ are used, <m/dead/ has precendence.
2133

    
2134
	<tag>rx buffer <M>num</M></tag>
2135
	 This sets the size of buffer used for receiving packets. The buffer should
2136
	 be bigger than maximal size of any packets. Value NORMAL (default)
2137
	 means 2*MTU, value LARGE means maximal allowed packet - 65535.
2138

    
2139
	<tag>type broadcast|bcast</tag>
2140
	 BIRD detects a type of a connected network automatically, but
2141
	 sometimes it's convenient to force use of a different type
2142
	 manually. On broadcast networks (like ethernet), flooding
2143
	 and Hello messages are sent using multicasts (a single packet
2144
	 for all the neighbors). A designated router is elected and it
2145
	 is responsible for synchronizing the link-state databases and
2146
	 originating network LSAs. This network type cannot be used on
2147
	 physically NBMA networks and on unnumbered networks (networks
2148
	 without proper IP prefix).
2149

    
2150
	<tag>type pointopoint|ptp</tag>
2151
	 Point-to-point networks connect just 2 routers together. No
2152
	 election is performed and no network LSA is originated, which
2153
	 makes it simpler and faster to establish. This network type
2154
	 is useful not only for physically PtP ifaces (like PPP or
2155
	 tunnels), but also for broadcast networks used as PtP links.
2156
	 This network type cannot be used on physically NBMA networks.
2157

    
2158
	<tag>type nonbroadcast|nbma</tag>
2159
	 On NBMA networks, the packets are sent to each neighbor
2160
	 separately because of lack of multicast capabilities.
2161
	 Like on broadcast networks, a designated router is elected,
2162
	 which plays a central role in propagation of LSAs.
2163
	 This network type cannot be used on unnumbered networks.
2164

    
2165
	<tag>type pointomultipoint|ptmp</tag>
2166
	 This is another network type designed to handle NBMA
2167
	 networks. In this case the NBMA network is treated as a
2168
	 collection of PtP links. This is useful if not every pair of
2169
	 routers on the NBMA network has direct communication, or if
2170
	 the NBMA network is used as an (possibly unnumbered) PtP
2171
	 link.
2172

    
2173
	<tag>strict nonbroadcast <M>switch</M></tag>
2174
	 If set, don't send hello to any undefined neighbor. This switch
2175
	 is ignored on other than NBMA or PtMP networks. Default value is no.
2176

    
2177
	<tag>real broadcast <m/switch/</tag>
2178
	 In <cf/type broadcast/ or <cf/type ptp/ network
2179
	 configuration, OSPF packets are sent as IP multicast
2180
	 packets. This option changes the behavior to using
2181
	 old-fashioned IP broadcast packets. This may be useful as a
2182
	 workaround if IP multicast for some reason does not work or
2183
	 does not work reliably. This is a non-standard option and
2184
	 probably is not interoperable with other OSPF
2185
	 implementations. Default value is no.
2186

    
2187
	<tag>check link <M>switch</M></tag>
2188
	 If set, a hardware link state (reported by OS) is taken into
2189
	 consideration. When a link disappears (e.g. an ethernet cable is
2190
	 unplugged), neighbors are immediately considered unreachable
2191
	 and only the address of the iface (instead of whole network
2192
	 prefix) is propagated. It is possible that some hardware
2193
	 drivers or platforms do not implement this feature. Default value is no.
2194

    
2195
	<tag>ecmp weight <M>num</M></tag>
2196
	 When ECMP (multipath) routes are allowed, this value specifies
2197
	 a relative weight used for nexthops going through the iface.
2198
	 Allowed values are 1-256. Default value is 1.
2199

    
2200
	<tag>authentication none</tag>
2201
	 No passwords are sent in OSPF packets. This is the default value.
2202

    
2203
	<tag>authentication simple</tag>
2204
	 Every packet carries 8 bytes of password. Received packets
2205
	 lacking this password are ignored. This authentication mechanism is
2206
	 very weak.
2207

    
2208
	<tag>authentication cryptographic</tag>
2209
	 16-byte long MD5 digest is appended to every packet. For the digest
2210
         generation 16-byte long passwords are used. Those passwords are 
2211
         not sent via network, so this mechanism is quite secure.
2212
         Packets can still be read by an attacker.
2213

    
2214
	<tag>password "<M>text</M>"</tag>
2215
	 An 8-byte or 16-byte password used for authentication.
2216
	 See <ref id="dsc-pass" name="password"> common option for detailed description.
2217

    
2218
	<tag>neighbors { <m/set/ } </tag>
2219
	 A set of neighbors to which Hello messages on NBMA or PtMP
2220
	 networks are to be sent. For NBMA networks, some of them
2221
	 could be marked as eligible.
2222

    
2223
</descrip>
2224

    
2225
<sect1>Attributes
2226

    
2227
<p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
2228
Metric is ranging from 1 to infinity (65535).
2229
External routes use <cf/metric type 1/ or <cf/metric type 2/.
2230
A <cf/metric of type 1/ is comparable with internal <cf/metric/, a
2231
<cf/metric of type 2/ is always longer
2232
than any <cf/metric of type 1/ or any <cf/internal metric/.
2233
<cf/Internal metric/ or <cf/metric of type 1/ is stored in attribute
2234
<cf/ospf_metric1/, <cf/metric type 2/ is stored in attribute <cf/ospf_metric2/.
2235
If you specify both metrics only metric1 is used.
2236

    
2237
Each external route can also carry attribute <cf/ospf_tag/ which is a
2238
32-bit integer which is used when exporting routes to other protocols;
2239
otherwise, it doesn't affect routing inside the OSPF domain at all.
2240
The fourth attribute <cf/ospf_router_id/ is a router ID of the router
2241
advertising that route/network. This attribute is read-only. Default
2242
is <cf/ospf_metric2 = 10000/ and <cf/ospf_tag = 0/.
2243

    
2244
<sect1>Example
2245

    
2246
<p>
2247

    
2248
<code>
2249
protocol ospf MyOSPF {
2250
        rfc1583compat yes;
2251
        tick 2;
2252
	export filter {
2253
		if source = RTS_BGP then {
2254
			ospf_metric1 = 100;
2255
			accept;
2256
		}
2257
		reject;
2258
	};
2259
	area 0.0.0.0 {
2260
		interface "eth*" {
2261
			cost 11;
2262
			hello 15;
2263
			priority 100;
2264
			retransmit 7;
2265
			authentication simple;
2266
			password "aaa";
2267
		};
2268
		interface "ppp*" {
2269
			cost 100;
2270
			authentication cryptographic;
2271
			password "abc" {
2272
				id 1;
2273
				generate to "22-04-2003 11:00:06";
2274
				accept from "17-01-2001 12:01:05";
2275
			};
2276
			password "def" {
2277
				id 2;
2278
				generate to "22-07-2005 17:03:21";
2279
				accept from "22-02-2001 11:34:06";
2280
			};
2281
		};
2282
		interface "arc0" {
2283
			cost 10;
2284
			stub yes;
2285
		};
2286
		interface "arc1";
2287
	};
2288
	area 120 {
2289
		stub yes;
2290
		networks {
2291
			172.16.1.0/24;
2292
			172.16.2.0/24 hidden;
2293
		}
2294
		interface "-arc0" , "arc*" {
2295
			type nonbroadcast;
2296
			authentication none;
2297
			strict nonbroadcast yes;
2298
			wait 120;
2299
			poll 40;
2300
			dead count 8;
2301
			neighbors {
2302
				192.168.120.1 eligible;
2303
				192.168.120.2;
2304
				192.168.120.10;
2305
			};
2306
		};
2307
	};
2308
}
2309
</code>
2310

    
2311
<sect>Pipe
2312

    
2313
<sect1>Introduction
2314

    
2315
<p>The Pipe protocol serves as a link between two routing tables, allowing routes to be
2316
passed from a table declared as primary (i.e., the one the pipe is connected to using the
2317
<cf/table/ configuration keyword) to the secondary one (declared using <cf/peer table/)
2318
and vice versa, depending on what's allowed by the filters. Export filters control export
2319
of routes from the primary table to the secondary one, import filters control the opposite
2320
direction.
2321

    
2322
<p>The Pipe protocol may work in the transparent mode mode or in the opaque mode.
2323
In the transparent mode, the Pipe protocol retransmits all routes from
2324
one table to the other table, retaining their original source and
2325
attributes.  If import and export filters are set to accept, then both
2326
tables would have the same content. The transparent mode is the default mode.
2327

    
2328
<p>In the opaque mode, the Pipe protocol retransmits optimal route
2329
from one table to the other table in a similar way like other
2330
protocols send and receive routes. Retransmitted route will have the
2331
source set to the Pipe protocol, which may limit access to protocol
2332
specific route attributes. This mode is mainly for compatibility, it
2333
is not suggested for new configs. The mode can be changed by
2334
<tt/mode/ option.
2335

    
2336
<p>The primary use of multiple routing tables and the Pipe protocol is for policy routing,
2337
where handling of a single packet doesn't depend only on its destination address, but also
2338
on its source address, source interface, protocol type and other similar parameters.
2339
In many systems (Linux being a good example), the kernel allows to enforce routing policies
2340
by defining routing rules which choose one of several routing tables to be used for a packet
2341
according to its parameters. Setting of these rules is outside the scope of BIRD's work
2342
(on Linux, you can use the <tt/ip/ command), but you can create several routing tables in BIRD,
2343
connect them to the kernel ones, use filters to control which routes appear in which tables
2344
and also you can employ the Pipe protocol for exporting a selected subset of one table to
2345
another one.
2346

    
2347
<sect1>Configuration
2348

    
2349
<p><descrip>
2350
	<tag>peer table <m/table/</tag> Defines secondary routing table to connect to. The
2351
	primary one is selected by the <cf/table/ keyword.
2352

    
2353
	<tag>mode opaque|transparent</tag> Specifies the mode for the pipe to work in. Default is opaque.
2354
</descrip>
2355

    
2356
<sect1>Attributes
2357

    
2358
<p>The Pipe protocol doesn't define any route attributes.
2359

    
2360
<sect1>Example
2361

    
2362
<p>Let's consider a router which serves as a boundary router of two different autonomous
2363
systems, each of them connected to a subset of interfaces of the router, having its own
2364
exterior connectivity and wishing to use the other AS as a backup connectivity in case
2365
of outage of its own exterior line.
2366

    
2367
<p>Probably the simplest solution to this situation is to use two routing tables (we'll
2368
call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that packets having
2369
arrived from interfaces belonging to the first AS will be routed according to <cf/as1/
2370
and similarly for the second AS. Thus we have split our router to two logical routers,
2371
each one acting on its own routing table, having its own routing protocols on its own
2372
interfaces. In order to use the other AS's routes for backup purposes, we can pass
2373
the routes between the tables through a Pipe protocol while decreasing their preferences
2374
and correcting their BGP paths to reflect the AS boundary crossing.
2375

    
2376
<code>
2377
table as1;				# Define the tables
2378
table as2;
2379

    
2380
protocol kernel kern1 {			# Synchronize them with the kernel
2381
	table as1;
2382
	kernel table 1;
2383
}
2384

    
2385
protocol kernel kern2 {
2386
	table as2;
2387
	kernel table 2;
2388
}
2389

    
2390
protocol bgp bgp1 {			# The outside connections
2391
	table as1;
2392
	local as 1;
2393
	neighbor 192.168.0.1 as 1001;
2394
	export all;
2395
	import all;
2396
}
2397

    
2398
protocol bgp bgp2 {
2399
	table as2;
2400
	local as 2;
2401
	neighbor 10.0.0.1 as 1002;
2402
	export all;
2403
	import all;
2404
}
2405

    
2406
protocol pipe {				# The Pipe
2407
	table as1;
2408
	peer table as2;
2409
	export filter {
2410
		if net ~ [ 1.0.0.0/8+] then {	# Only AS1 networks
2411
			if preference>10 then preference = preference-10;
2412
			if source=RTS_BGP then bgp_path.prepend(1);
2413
			accept;
2414
		}
2415
		reject;
2416
	};
2417
	import filter {
2418
		if net ~ [ 2.0.0.0/8+] then {	# Only AS2 networks
2419
			if preference>10 then preference = preference-10;
2420
			if source=RTS_BGP then bgp_path.prepend(2);
2421
			accept;
2422
		}
2423
		reject;
2424
	};
2425
}
2426
</code>
2427

    
2428
<sect>RAdv
2429

    
2430
<sect1>Introduction
2431

    
2432
<p>The RAdv protocol is an implementation of Router Advertisements,
2433
which are used in the IPv6 stateless autoconfiguration. IPv6 routers
2434
send (in irregular time intervals or as an answer to a request)
2435
advertisement packets to connected networks. These packets contain
2436
basic information about a local network (e.g. a list of network
2437
prefixes), which allows network hosts to autoconfigure network
2438
addresses and choose a default route. BIRD implements router behavior
2439
as defined in
2440
RFC 4861<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4861.txt">
2441
and also the DNS extensions from
2442
RFC 6106<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc6106.txt">.
2443

    
2444
<sect1>Configuration
2445

    
2446
<p>There are several classes of definitions in RAdv configuration --
2447
interface definitions, prefix definitions and DNS definitions:
2448

    
2449
<descrip>
2450
	<tag>interface <m/pattern [, ...]/  { <m/options/ }</tag>
2451
	Interface definitions specify a set of interfaces on which the
2452
	protocol is activated and contain interface specific options.
2453
	See <ref id="dsc-iface" name="interface"> common options for
2454
	detailed description.
2455

    
2456
	<tag>prefix <m/prefix/ { <m/options/ }</tag>
2457
	Prefix definitions allow to modify a list of advertised
2458
	prefixes. By default, the advertised prefixes are the same as
2459
	the network prefixes assigned to the interface. For each
2460
	network prefix, the matching prefix definition is found and
2461
	its options are used. If no matching prefix definition is
2462
	found, the prefix is used with default options.
2463

    
2464
	Prefix definitions can be either global or interface-specific.
2465
	The second ones are part of interface options. The prefix
2466
	definition matching is done in the first-match style, when
2467
	interface-specific definitions are processed before global
2468
	definitions. As expected, the prefix definition is matching if
2469
	the network prefix is a subnet of the prefix in prefix
2470
	definition.
2471

    
2472
	<tag>rdnss { <m/options/ }</tag>
2473
	RDNSS definitions allow to specify a list of advertised
2474
	recursive DNS servers together with their options. As options
2475
	are seldom necessary, there is also a short variant <cf>rdnss
2476
	<m/address/</cf> that just specifies one DNS server. Multiple
2477
	definitions are cumulative. RDNSS definitions may also be
2478
	interface-specific when used inside interface options. By
2479
	default, interface uses both global and interface-specific
2480
	options, but that can be changed by <cf/rdnss local/ option.
2481

    
2482
	<tag>dnssl { <m/options/ }</tag>
2483
	DNSSL definitions allow to specify a list of advertised DNS
2484
	search domains together with their options. Like <cf/rdnss/
2485
	above, multiple definitions are cumulative, they can be used
2486
	also as interface-specific options and there is a short
2487
	variant <cf>dnssl <m/domain/</cf> that just specifies one DNS
2488
        search domain.
2489

    
2490
	<label id="dsc-trigger"> <tag>trigger <m/prefix/</tag>
2491
	RAdv protocol could be configured to change its behavior based
2492
	on availability of routes. When this option is used, the
2493
	protocol waits in suppressed state until a <it/trigger route/
2494
	(for the specified network) is exported to the protocol, the
2495
	protocol also returnsd to suppressed state if the
2496
	<it/trigger route/ disappears. Note that route export depends
2497
	on specified export filter, as usual. This option could be
2498
	used, e.g., for handling failover in multihoming scenarios.
2499

    
2500
	During suppressed state, router advertisements are generated,
2501
	but with some fields zeroed. Exact behavior depends on which
2502
	fields are zeroed, this can be configured by
2503
	<cf/sensitive/ option for appropriate fields. By default, just
2504
	<cf/default lifetime/ (also called <cf/router lifetime/) is
2505
	zeroed, which means hosts cannot use the router as a default
2506
	router. <cf/preferred lifetime/ and <cf/valid lifetime/ could
2507
	also be configured as <cf/sensitive/ for a prefix, which would
2508
	cause autoconfigured IPs to be deprecated or even removed.
2509
</descrip>
2510

    
2511
<p>Interface specific options:
2512

    
2513
<descrip>
2514
	<tag>max ra interval <m/expr/</tag>
2515
	Unsolicited router advertisements are sent in irregular time
2516
	intervals. This option specifies the maximum length of these
2517
	intervals, in seconds. Valid values are 4-1800. Default: 600
2518

    
2519
	<tag>min ra interval <m/expr/</tag>
2520
	This option specifies the minimum length of that intervals, in
2521
	seconds. Must be at least 3 and at most 3/4 * <cf/max ra interval/.
2522
	Default: about 1/3 * <cf/max ra interval/.
2523

    
2524
	<tag>min delay <m/expr/</tag>
2525
	The minimum delay between two consecutive router advertisements,
2526
	in seconds. Default: 3
2527

    
2528
	<tag>managed <m/switch/</tag>
2529
	This option specifies whether hosts should use DHCPv6 for
2530
	IP address configuration. Default: no
2531

    
2532
	<tag>other config <m/switch/</tag>
2533
	This option specifies whether hosts should use DHCPv6 to
2534
	receive other configuration information. Default: no
2535

    
2536
	<tag>link mtu <m/expr/</tag>
2537
	This option specifies which value of MTU should be used by
2538
	hosts. 0 means unspecified. Default: 0
2539

    
2540
	<tag>reachable time <m/expr/</tag>
2541
	This option specifies the time (in milliseconds) how long
2542
	hosts should assume a neighbor is reachable (from the last
2543
	confirmation). Maximum is 3600000, 0 means unspecified.
2544
	Default 0.
2545

    
2546
	<tag>retrans timer <m/expr/</tag>
2547
	This option specifies the time (in milliseconds) how long
2548
	hosts should wait before retransmitting Neighbor Solicitation
2549
	messages. 0 means unspecified. Default 0.
2550

    
2551
	<tag>current hop limit <m/expr/</tag>
2552
	This option specifies which value of Hop Limit should be used
2553
	by hosts. Valid values are 0-255, 0 means unspecified. Default: 64
2554

    
2555
	<tag>default lifetime <m/expr/ [sensitive <m/switch/]</tag>
2556
	This option specifies the time (in seconds) how long (after
2557
	the receipt of RA) hosts may use the router as a default
2558
	router. 0 means do not use as a default router. For
2559
	<cf/sensitive/ option, see <ref id="dsc-trigger" name="trigger">.
2560
	Default: 3 * <cf/max ra interval/, <cf/sensitive/ yes.
2561

    
2562
	<tag>rdnss local <m/switch/</tag>
2563
	Use only local (interface-specific) RDNSS definitions for this
2564
	interface. Otherwise, both global and local definitions are
2565
	used. Could also be used to disable RDNSS for given interface
2566
	if no local definitons are specified. Default: no.
2567

    
2568
	<tag>dnssl local <m/switch/</tag>
2569
	Use only local DNSSL definitions for this interface. See
2570
	<cf/rdnss local/ option above. Default: no.
2571
</descrip>
2572

    
2573

    
2574
<p>Prefix specific options:
2575

    
2576
<descrip>
2577
	<tag>skip <m/switch/</tag>
2578
	This option allows to specify that given prefix should not be
2579
	advertised. This is useful for making exceptions from a
2580
	default policy of advertising all prefixes. Note that for
2581
	withdrawing an already advertised prefix it is more useful to
2582
	advertise it with zero valid lifetime. Default: no
2583

    
2584
	<tag>onlink <m/switch/</tag>
2585
	This option specifies whether hosts may use the advertised
2586
	prefix for onlink determination. Default: yes
2587

    
2588
	<tag>autonomous <m/switch/</tag>
2589
	This option specifies whether hosts may use the advertised
2590
	prefix for stateless autoconfiguration. Default: yes
2591

    
2592
	<tag>valid lifetime <m/expr/ [sensitive <m/switch/]</tag>
2593
	This option specifies the time (in seconds) how long (after
2594
	the receipt of RA) the prefix information is valid, i.e.,
2595
	autoconfigured IP addresses can be assigned and hosts with
2596
	that IP addresses are considered directly reachable. 0 means
2597
	the prefix is no longer valid. For <cf/sensitive/ option, see
2598
	<ref id="dsc-trigger" name="trigger">. Default: 86400 (1 day), <cf/sensitive/ no.
2599

    
2600
	<tag>preferred lifetime <m/expr/ [sensitive <m/switch/]</tag>
2601
	This option specifies the time (in seconds) how long (after
2602
	the receipt of RA) IP addresses generated from the prefix
2603
	using stateless autoconfiguration remain preferred. For
2604
	<cf/sensitive/ option, see <ref id="dsc-trigger" name="trigger">.
2605
	Default: 14400 (4 hours), <cf/sensitive/ no.
2606
</descrip>
2607

    
2608

    
2609
<p>RDNSS specific options:
2610

    
2611
<descrip>
2612
	<tag>ns <m/address/</tag>
2613
	This option specifies one recursive DNS server. Can be used
2614
	multiple times for multiple servers. It is mandatory to have
2615
	at least one <cf/ns/ option in <cf/rdnss/ definition.
2616

    
2617
	<tag>lifetime [mult] <m/expr/</tag>
2618
	This option specifies the time how long the RDNSS information
2619
        may be used by clients after the receipt of RA. It is
2620
        expressed either in seconds or (when <cf/mult/ is used) in
2621
        multiples of <cf/max ra interval/. Note that RDNSS information
2622
        is also invalidated when <cf/default lifetime/ expires. 0
2623
        means these addresses are no longer valid DNS servers.
2624
	Default: 3 * <cf/max ra interval/.
2625
</descrip>
2626

    
2627

    
2628
<p>DNSSL specific options:
2629

    
2630
<descrip>
2631
	<tag>domain <m/address/</tag>
2632
	This option specifies one DNS search domain. Can be used
2633
	multiple times for multiple domains. It is mandatory to have
2634
	at least one <cf/domain/ option in <cf/dnssl/ definition.
2635

    
2636
	<tag>lifetime [mult] <m/expr/</tag>
2637
	This option specifies the time how long the DNSSL information
2638
        may be used by clients after the receipt of RA. Details are
2639
	the same as for RDNSS <cf/lifetime/ option above.
2640
	Default: 3 * <cf/max ra interval/.
2641
</descrip>
2642

    
2643

    
2644
<sect1>Example
2645

    
2646
<p><code>
2647
protocol radv {
2648
	interface "eth2" {
2649
		max ra interval 5;	# Fast failover with more routers
2650
		managed yes;		# Using DHCPv6 on eth2
2651
		prefix ::/0 {
2652
			autonomous off;	# So do not autoconfigure any IP
2653
		};
2654
	};
2655

    
2656
	interface "eth*";		# No need for any other options
2657

    
2658
	prefix 2001:0DB8:1234::/48 {
2659
		preferred lifetime 0;	# Deprecated address range
2660
	};
2661

    
2662
	prefix 2001:0DB8:2000::/48 {
2663
		autonomous off;		# Do not autoconfigure
2664
	};
2665

    
2666
	rdnss 2001:0DB8:1234::10;	# Short form of RDNSS
2667

    
2668
	rdnss {
2669
		lifetime mult 10;
2670
		ns 2001:0DB8:1234::11;
2671
		ns 2001:0DB8:1234::12;
2672
	};
2673

    
2674
	dnssl {
2675
		lifetime 3600;
2676
		domain "abc.com";
2677
		domain "xyz.com";
2678
	};
2679
}
2680
</code>
2681

    
2682
<sect>RIP
2683

    
2684
<sect1>Introduction
2685

    
2686
<p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol, where each router broadcasts (to all its neighbors)
2687
distances to all networks it can reach. When a router hears distance to another network, it increments
2688
it and broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some network goes
2689
unreachable, routers keep telling each other that its distance is the original distance plus 1 (actually, plus
2690
interface metric, which is usually one). After some time, the distance reaches infinity (that's 15 in
2691
RIP) and all routers know that network is unreachable. RIP tries to minimize situations where
2692
counting to infinity is necessary, because it is slow. Due to infinity being 16, you can't use
2693
RIP on networks where maximal distance is higher than 15 hosts. You can read more about RIP at <HTMLURL
2694
URL="http://www.ietf.org/html.charters/rip-charter.html" name="http://www.ietf.org/html.charters/rip-charter.html">. Both IPv4  
2695
(RFC 1723<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1723.txt">)
2696
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
2697
not currently supported. RIPv4 MD5 authentication (RFC 2082<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2082.txt">) is supported.
2698

    
2699
<p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
2700
convergence, big network load and inability to handle larger networks
2701
makes it pretty much obsolete. (It is still usable on very small networks.)
2702

    
2703
<sect1>Configuration
2704

    
2705
<p>In addition to options common for all to other protocols, RIP supports the following ones:
2706

    
2707
<descrip>
2708
	<tag/authentication none|plaintext|md5/ selects authentication method to be used. <cf/none/ means that
2709
	  packets are not authenticated at all, <cf/plaintext/ means that a plaintext password is embedded
2710
	  into each packet, and <cf/md5/ means that packets are authenticated using a MD5 cryptographic
2711
	  hash. If you set authentication to not-none, it is a good idea to add <cf>password</cf>
2712
	  section. Default: none.
2713

    
2714
	<tag>honor always|neighbor|never </tag>specifies when should requests for dumping routing table
2715
	  be honored. (Always, when sent from a  host on a directly connected
2716
	  network or never.) Routing table updates are honored only from
2717
	  neighbors, that is not configurable. Default: never.
2718
</descrip>
2719

    
2720
<p>There are two options that can be specified per-interface. First is <cf>metric</cf>, with
2721
default one.  Second is <cf>mode multicast|broadcast|quiet|nolisten|version1</cf>, it selects mode for
2722
rip to work in. If nothing is specified, rip runs in multicast mode. <cf>version1</cf> is
2723
currently equivalent to <cf>broadcast</cf>, and it makes RIP talk to a broadcast address even
2724
through multicast mode is possible. <cf>quiet</cf> option means that RIP will not transmit
2725
any periodic messages to this interface and <cf>nolisten</cf> means that RIP will send to this
2726
interface but not listen to it.
2727

    
2728
<p>The following options generally override behavior specified in RFC. If you use any of these
2729
options, BIRD will no longer be RFC-compliant, which means it will not be able to talk to anything
2730
other than equally configured BIRD. I have warned you.
2731

    
2732
<descrip>
2733
	<tag>port <M>number</M></tag>
2734
	  selects IP port to operate on, default 520. (This is useful when testing BIRD, if you
2735
	  set this to an address &gt;1024, you will not need to run bird with UID==0).
2736

    
2737
	<tag>infinity <M>number</M></tag>
2738
	  selects the value of infinity, default is 16. Bigger values will make protocol convergence
2739
	  even slower.
2740

    
2741
	<tag>period <M>number</M>
2742
	  </tag>specifies the number of seconds between periodic updates. Default is 30 seconds. A lower
2743
	  number will mean faster convergence but bigger network
2744
	  load. Do not use values lower than 12.
2745

    
2746
	<tag>timeout time <M>number</M>
2747
	  </tag>specifies how old route has to be to be considered unreachable. Default is 4*<cf/period/.
2748

    
2749
	<tag>garbage time <M>number</M>
2750
	  </tag>specifies how old route has to be to be discarded. Default is 10*<cf/period/.
2751
</descrip>
2752

    
2753
<sect1>Attributes
2754

    
2755
<p>RIP defines two route attributes:
2756

    
2757
<descrip>
2758
	<tag>int <cf/rip_metric/</tag> RIP metric of the route (ranging from 0 to <cf/infinity/).
2759
	When routes from different RIP instances are available and all of them have the same
2760
	preference, BIRD prefers the route with lowest <cf/rip_metric/.
2761
	When importing a non-RIP route, the metric defaults to 5.
2762

    
2763
	<tag>int <cf/rip_tag/</tag> RIP route tag: a 16-bit number which can be used
2764
	to carry additional information with the route (for example, an originating AS number
2765
	in case of external routes). When importing a non-RIP route, the tag defaults to 0.
2766
</descrip>
2767

    
2768
<sect1>Example
2769

    
2770
<p><code>
2771
protocol rip MyRIP_test {
2772
        debug all;
2773
        port 1520;
2774
        period 12;
2775
        garbage time 60;
2776
        interface "eth0" { metric 3; mode multicast; };
2777
	interface "eth*" { metric 2; mode broadcast; };
2778
        honor neighbor;
2779
        authentication none;
2780
        import filter { print "importing"; accept; };
2781
        export filter { print "exporting"; accept; };
2782
}
2783
</code>
2784

    
2785
<sect>Static
2786

    
2787
<p>The Static protocol doesn't communicate with other routers in the network,
2788
but instead it allows you to define routes manually. This is often used for
2789
specifying how to forward packets to parts of the network which don't use
2790
dynamic routing at all and also for defining sink routes (i.e., those
2791
telling to return packets as undeliverable if they are in your IP block,
2792
you don't have any specific destination for them and you don't want to send
2793
them out through the default route to prevent routing loops).
2794

    
2795
<p>There are five types of static routes: `classical' routes telling
2796
to forward packets to a neighboring router, multipath routes
2797
specifying several (possibly weighted) neighboring routers, device
2798
routes specifying forwarding to hosts on a directly connected network,
2799
recursive routes computing their nexthops by doing route table lookups
2800
for a given IP and special routes (sink, blackhole etc.) which specify
2801
a special action to be done instead of forwarding the packet.
2802

    
2803
<p>When the particular destination is not available (the interface is down or
2804
the next hop of the route is not a neighbor at the moment), Static just
2805
uninstalls the route from the table it is connected to and adds it again as soon
2806
as the destination becomes adjacent again.
2807

    
2808
<p>The Static protocol does not have many configuration options. The
2809
definition of the protocol contains mainly a list of static routes:
2810

    
2811
<descrip>
2812
	<tag>route <m/prefix/ via <m/ip/</tag> Static route through
2813
	a neighboring router.
2814
	<tag>route <m/prefix/ multipath via <m/ip/ [weight <m/num/] [via ...]</tag>
2815
	Static multipath route. Contains several nexthops (gateways), possibly
2816
 	with their weights.
2817
	<tag>route <m/prefix/ via <m/"interface"/</tag> Static device
2818
	route through an interface to hosts on a directly connected network.
2819
	<tag>route <m/prefix/ recursive <m/ip/</tag> Static recursive route,
2820
	its nexthop depends on a route table lookup for given IP address.
2821
	<tag>route <m/prefix/ blackhole|unreachable|prohibit</tag> Special routes
2822
	specifying to silently drop the packet, return it as unreachable or return
2823
	it as administratively prohibited. First two targets are also known
2824
	as <cf/drop/ and <cf/reject/.
2825

    
2826
	<tag>check link <m/switch/</tag>
2827
	If set, hardware link states of network interfaces are taken
2828
	into consideration.  When link disappears (e.g. ethernet cable
2829
	is unplugged), static routes directing to that interface are
2830
	removed. It is possible that some hardware drivers or
2831
	platforms do not implement this feature. Default: off.
2832

    
2833
	<tag>igp table <m/name/</tag> Specifies a table that is used
2834
	for route table lookups of recursive routes. Default: the
2835
	same table as the protocol is connected to.
2836
</descrip>
2837

    
2838
<p>Static routes have no specific attributes.
2839

    
2840
<p>Example static config might look like this:
2841

    
2842
<p><code>
2843
protocol static {
2844
	table testable;			 # Connect to a non-default routing table
2845
	route 0.0.0.0/0 via 198.51.100.130; # Default route
2846
	route 10.0.0.0/8 multipath	 # Multipath route
2847
		via 198.51.100.10 weight 2
2848
		via 198.51.100.20
2849
		via 192.0.2.1;
2850
	route 203.0.113.0/24 unreachable; # Sink route
2851
	route 10.2.0.0/24 via "arc0";	 # Secondary network
2852
}
2853
</code>
2854

    
2855
<chapt>Conclusions
2856

    
2857
<sect>Future work
2858

    
2859
<p>Although BIRD supports all the commonly used routing protocols,
2860
there are still some features which would surely deserve to be
2861
implemented in future versions of BIRD:
2862

    
2863
<itemize>
2864
<item>Opaque LSA's
2865
<item>Route aggregation and flap dampening
2866
<item>Multipath routes
2867
<item>Multicast routing protocols
2868
<item>Ports to other systems
2869
</itemize>
2870

    
2871
<sect>Getting more help
2872

    
2873
<p>If you use BIRD, you're welcome to join the bird-users mailing list
2874
(<HTMLURL URL="mailto:bird-users@bird.network.cz" name="bird-users@bird.network.cz">)
2875
where you can share your experiences with the other users and consult
2876
your problems with the authors. To subscribe to the list, just send a
2877
<tt/subscribe bird-users/ command in a body of a mail to
2878
(<HTMLURL URL="mailto:majordomo@bird.network.cz" name="majordomo@bird.network.cz">).
2879
The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
2880

    
2881
<p>BIRD is a relatively young system and it probably contains some
2882
bugs. You can report any problems to the bird-users list and the authors
2883
will be glad to solve them, but before you do so,
2884
please make sure you have read the available documentation and that you are running the latest version (available at <HTMLURL
2885
URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">). (Of course, a patch
2886
which fixes the bug is always welcome as an attachment.)
2887

    
2888
<p>If you want to understand what is going inside, Internet standards are
2889
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">).
2890

    
2891
<p><it/Good luck!/
2892

    
2893
</book>
2894

    
2895
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2896
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