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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
Many commands have the <m/name/ of the protocol instance as an argument.
627
This argument can be omitted if there exists only a single instance.
628

    
629
<p>Here is a brief list of supported functions:
630

    
631
<descrip>
632
	<tag>dump resources|sockets|interfaces|neighbors|attributes|routes|protocols</tag>
633
	Dump contents of internal data structures to the debugging output.
634

    
635
	<tag>show status</tag>
636
	Show router status, that is BIRD version, uptime and time from last reconfiguration.
637

    
638
	<tag>show protocols [all]</tag>
639
	Show list of protocol instances along with tables they are connected to and protocol status, possibly giving verbose information, if <cf/all/ is specified.
640

    
641
	<tag>show ospf interface [<m/name/] ["<m/interface/"]</tag>
642
	Show detailed information about OSPF interfaces.
643

    
644
	<tag>show ospf neighbors [<m/name/] ["<m/interface/"]</tag>
645
	Show a list of OSPF neighbors and a state of adjacency to them.
646

    
647
	<tag>show ospf state [all] [<m/name/]</tag>
648
	Show detailed information about OSPF areas based on a content
649
	of the link-state database. It shows network topology, stub
650
	networks, aggregated networks and routers from other areas and
651
	external routes. The command shows information about reachable
652
	network nodes, use option <cf/all/ to show information about
653
	all network nodes in the link-state database.
654

    
655
	<tag>show ospf topology [all] [<m/name/]</tag>
656
	Show a topology of OSPF areas based on a content of the
657
	link-state database.  It is just a stripped-down version of
658
	'show ospf state'.
659

    
660
	<tag>show ospf lsadb [global | area <m/id/ | link] [type <m/num/] [lsid <m/id/] [self | router <m/id/] [<m/name/] </tag>
661
	Show contents of an OSPF LSA database. Options could be used to filter entries.
662

    
663
	<tag>show static [<m/name/]</tag>
664
	Show detailed information about static routes.
665

    
666
	<tag>show interfaces [summary]</tag>
667
	Show the list of interfaces. For each interface, print its type, state, MTU and addresses assigned. 
668

    
669
	<tag>show symbols [table|filter|function|protocol|template|roa|<m/symbol/]</tag>
670
	Show the list of symbols defined in the configuration (names of protocols, routing tables etc.).
671

    
672
	<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>
673
	Show contents of a routing table (by default of the main one or
674
        the table attached to a respective protocol),
675
	that is routes, their metrics and (in case the <cf/all/ switch is given)
676
	all their attributes.
677

    
678
	<p>You can specify a <m/prefix/ if you want to print routes for a
679
	specific network. If you use <cf>for <m/prefix or IP/</cf>, you'll get
680
	the entry which will be used for forwarding of packets to the given
681
	destination. By default, all routes for each network are printed with
682
	the selected one at the top, unless <cf/primary/ is given in which case
683
	only the selected route is shown.
684

    
685
	<p>You can also ask for printing only routes processed and accepted by
686
	a given filter (<cf>filter <m/name/</cf> or <cf>filter { <m/filter/ }
687
	</cf> or matching a given condition (<cf>where <m/condition/</cf>).
688
	The <cf/export/ and <cf/preexport/ switches ask for printing of entries
689
	that are exported to the specified protocol. With <cf/preexport/, the
690
	export filter of the protocol is skipped.
691

    
692
	<p>You can also select just routes added by a specific protocol.
693
	<cf>protocol <m/p/</cf>.
694

    
695
	<p>If BIRD is configured to keep filtered routes (see <cf/import keep filtered/
696
	option), you can show them instead of routes by using <cf/filtered/ switch.
697

    
698
	<p>The <cf/stats/ switch requests showing of route statistics (the
699
	number of networks, number of routes before and after filtering). If
700
	you use <cf/count/ instead, only the statistics will be printed.
701

    
702
	<tag>show roa [<m/prefix/ | in <m/prefix/ | for <m/prefix/] [as <m/num/] [table <m/t/>]</tag>
703
	Show contents of a ROA table (by default of the first one).
704
	You can specify a <m/prefix/ to print ROA entries for a
705
	specific network. If you use <cf>for <m/prefix/</cf>, you'll
706
	get all entries relevant for route validation of the network
707
	prefix; i.e., ROA entries whose prefixes cover the network
708
	prefix. Or you can use <cf>in <m/prefix/</cf> to get ROA entries
709
	covered by the network prefix. You could also use <cf/as/ option
710
	to show just entries for given AS.
711

    
712
	<tag>add roa <m/prefix/ max <m/num/] as <m/num/ [table <m/t/>]</tag>
713
	Add a new ROA entry to a ROA table. Such entry is called
714
	<it/dynamic/ compared to <it/static/ entries specified in the
715
	config file. These dynamic entries survive reconfiguration.
716

    
717
	<tag>delete roa <m/prefix/ max <m/num/] as <m/num/ [table <m/t/>]</tag>
718
	Delete the specified ROA entry from a ROA table. Only dynamic
719
	ROA entries (i.e., the ones added by <cf/add roa/ command) can
720
	be deleted.
721

    
722
	<tag>flush roa [table <m/t/>]</tag>
723
	Remove all dynamic ROA entries from a ROA table.
724

    
725
	<tag>configure [soft] ["<m/config file/"] [timeout [<m/num/]]</tag>
726
	Reload configuration from a given file. BIRD will smoothly
727
	switch itself to the new configuration, protocols are
728
	reconfigured if possible, restarted otherwise. Changes in
729
	filters usually lead to restart of affected protocols.
730

    
731
	If <cf/soft/ option is used, changes in filters does not cause
732
	BIRD to restart affected protocols, therefore already accepted
733
	routes (according to old filters) would be still propagated,
734
	but new routes would be processed according to the new
735
	filters.
736

    
737
	If <cf/timeout/ option is used, config timer is activated. The
738
	new configuration could be either confirmed using
739
	<cf/configure confirm/ command, or it will be reverted to the
740
	old one when the config timer expires. This is useful for cases
741
	when reconfiguration breaks current routing and a router becames
742
	inaccessible for an administrator. The config timeout expiration is
743
	equivalent to <cf/configure undo/ command. The timeout duration
744
	could be specified, default is 300 s.
745

    
746
	<tag>configure confirm</tag>
747
	Deactivate the config undo timer and therefore confirm the current
748
	configuration.
749

    
750
	<tag>configure undo</tag>
751
	Undo the last configuration change and smoothly switch back to
752
	the previous (stored) configuration. If the last configuration
753
	change was soft, the undo change is also soft. There is only
754
	one level of undo, but in some specific cases when several
755
	reconfiguration requests are given immediately in a row and
756
	the intermediate ones are skipped then the undo also skips them back.
757

    
758
	<tag>configure check ["<m/config file/"]</tag>
759
	Read and parse given config file, but do not use it. useful
760
	for checking syntactic and some semantic validity of an config
761
	file.
762

    
763
	<tag>enable|disable|restart <m/name/|"<m/pattern/"|all</tag>
764
	Enable, disable or restart a given protocol instance,
765
	instances matching the <cf><m/pattern/</cf> or
766
	<cf/all/ instances.
767

    
768
	<tag>reload [in|out] <m/name/|"<m/pattern/"|all</tag>
769
	
770
	Reload a given protocol instance, that means re-import routes
771
	from the protocol instance and re-export preferred routes to
772
	the instance. If <cf/in/ or <cf/out/ options are used, the
773
	command is restricted to one direction (re-import or
774
	re-export).
775

    
776
	This command is useful if appropriate filters have changed but
777
	the protocol instance was not restarted (or reloaded),
778
	therefore it still propagates the old set of routes. For example
779
	when <cf/configure soft/ command was used to change filters.
780

    
781
	Re-export always succeeds, but re-import is protocol-dependent
782
	and might fail (for example, if BGP neighbor does not support
783
	route-refresh extension). In that case, re-export is also
784
	skipped. Note that for the pipe protocol, both directions are
785
	always reloaded together (<cf/in/ or <cf/out/ options are
786
	ignored in that case).
787

    
788
	<tag/down/
789
	Shut BIRD down.
790

    
791
	<tag>debug <m/protocol/|<m/pattern/|all all|off|{ states | routes | filters | events | packets }</tag>
792
	Control protocol debugging.
793
</descrip>
794

    
795
<chapt>Filters
796

    
797
<sect>Introduction
798

    
799
<p>BIRD contains a simple programming language. (No, it can't yet read mail :-). There are
800
two objects in this language: filters and functions. Filters are interpreted by BIRD core when a route is
801
being passed between protocols and routing tables. The filter language contains control structures such
802
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>. 
803

    
804
<p>Filter gets the route, looks at its attributes and
805
modifies some of them if it wishes. At the end, it decides whether to
806
pass the changed route through (using <cf/accept/) or whether to <cf/reject/ it. A simple filter looks
807
like this:
808

    
809
<code>
810
filter not_too_far
811
int var;
812
{
813
	if defined( rip_metric ) then
814
		var = rip_metric;
815
	else {
816
		var = 1;
817
		rip_metric = 1;
818
	}
819
	if rip_metric &gt; 10 then
820
		reject "RIP metric is too big";
821
	else
822
		accept "ok";
823
}
824
</code>
825

    
826
<p>As you can see, a filter has a header, a list of local variables, and a body. The header consists of
827
the <cf/filter/ keyword followed by a (unique) name of filter. The list of local variables consists of
828
<cf><M>type name</M>;</cf> pairs where each pair defines one local variable. The body consists of
829
<cf> { <M>statements</M> }</cf>. Each <m/statement/ is terminated by a <cf/;/. You can group
830
several statements to a single compound statement by using braces (<cf>{ <M>statements</M> }</cf>) which is useful if
831
you want to make a bigger block of code conditional.
832

    
833
<p>BIRD supports functions, so that you don't have to repeat the same blocks of code over and
834
over. Functions can have zero or more parameters and they can have local variables. Recursion is not allowed. Function definitions
835
look like this:
836

    
837
<code>
838
function name ()
839
int local_variable;
840
{
841
	local_variable = 5;
842
}
843

    
844
function with_parameters (int parameter)
845
{
846
	print parameter;
847
}
848
</code>
849

    
850
<p>Unlike in C, variables are declared after the <cf/function/ line, but before the first <cf/{/. You can't declare
851
variables in nested blocks. Functions are called like in C: <cf>name();
852
with_parameters(5);</cf>. Function may return values using the <cf>return <m/[expr]/</cf>
853
command. Returning a value exits from current function (this is similar to C).
854

    
855
<p>Filters are declared in a way similar to functions except they can't have explicit
856
parameters. They get a route table entry as an implicit parameter, it is also passed automatically 
857
to any functions called. The filter must terminate with either
858
<cf/accept/ or <cf/reject/ statement. If there's a runtime error in filter, the route
859
is rejected. 
860

    
861
<p>A nice trick to debug filters is to use <cf>show route filter
862
<m/name/</cf> from the command line client. An example session might look
863
like:
864

    
865
<code>
866
pavel@bug:~/bird$ ./birdc -s bird.ctl
867
BIRD 0.0.0 ready.
868
bird> show route
869
10.0.0.0/8         dev eth0 [direct1 23:21] (240)
870
195.113.30.2/32    dev tunl1 [direct1 23:21] (240)
871
127.0.0.0/8        dev lo [direct1 23:21] (240)
872
bird> show route ?
873
show route [<prefix>] [table <t>] [filter <f>] [all] [primary]...
874
bird> show route filter { if 127.0.0.5 &tilde; net then accept; }
875
127.0.0.0/8        dev lo [direct1 23:21] (240)
876
bird>
877
</code>
878

    
879
<sect>Data types
880

    
881
<p>Each variable and each value has certain type. Booleans, integers and enums are
882
incompatible with each other (that is to prevent you from shooting in the foot).
883

    
884
<descrip>
885
	<tag/bool/ This is a boolean type, it can have only two values, <cf/true/ and
886
	  <cf/false/. Boolean is the only type you can use in <cf/if/
887
	  statements.
888

    
889
	<tag/int/ This is a general integer type, you can expect it to store signed values from -2000000000
890
	  to +2000000000. Overflows are not checked. You can use <cf/0x1234/ syntax to write hexadecimal values.
891

    
892
	<tag/pair/ This is a pair of two short integers. Each component can have values from 0 to
893
	  65535. Literals of this type are written as <cf/(1234,5678)/. The same syntax can also be
894
	  used to construct a pair from two arbitrary integer expressions (for example <cf/(1+2,a)/).
895

    
896
	<tag/quad/ This is a dotted quad of numbers used to represent
897
	  router IDs (and others).  Each component can have a value
898
	  from 0 to 255. Literals of this type are written like IPv4
899
	  addresses.
900

    
901
	<tag/string/ This is a string of characters. There are no ways to modify strings in
902
	  filters. You can pass them between functions, assign them to variables of type <cf/string/, print
903
	  such variables, but you can't concatenate two strings. String literals
904
	  are written as <cf/"This is a string constant"/.
905

    
906
	<tag/ip/ This type can hold a single IP address. Depending on the compile-time configuration of BIRD you are using, it
907
	  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>
908
	  on values of type ip. It masks out all but first <cf><M>num</M></cf> bits from the IP
909
	  address. So <cf/1.2.3.4.mask(8) = 1.0.0.0/ is true.
910

    
911
	<tag/prefix/ This type can hold a network prefix consisting of IP address and prefix length. Prefix literals are written as
912
	  <cf><M>ipaddress</M>/<M>pxlen</M></cf>, or
913
	  <cf><m>ipaddress</m>/<m>netmask</m></cf>. There are two special
914
	  operators on prefixes:
915
	  <cf/.ip/ which extracts the IP address from the pair, and <cf/.len/, which separates prefix
916
	  length from the pair. So <cf>1.2.0.0/16.pxlen = 16</cf> is true.
917

    
918
	<tag/ec/ This is a specialized type used to represent BGP
919
	  extended community values. It is essentially a 64bit value,
920
	  literals of this type are usually written as <cf>(<m/kind/,
921
	  <m/key/, <m/value/)</cf>, where <cf/kind/ is a kind of
922
	  extended community (e.g. <cf/rt/ / <cf/ro/ for a route
923
	  target / route origin communities), the format and possible
924
	  values of <cf/key/ and <cf/value/ are usually integers, but
925
	  it depends on the used kind. Similarly to pairs, ECs can be
926
	  constructed using expressions for <cf/key/ and
927
	  <cf/value/ parts, (e.g. <cf/(ro, myas, 3*10)/, where
928
	  <cf/myas/ is an integer variable).
929
 
930
	<tag/int|pair|quad|ip|prefix|ec|enum set/
931
	  Filters recognize four types of sets. Sets are similar to strings: you can pass them around
932
	  but you can't modify them. Literals of type <cf>int set</cf> look like <cf>
933
	  [ 1, 2, 5..7 ]</cf>. As you can see, both simple values and ranges are permitted in
934
	  sets.
935

    
936
	  For pair sets, expressions like <cf/(123,*)/ can be used to denote ranges (in
937
	  that case <cf/(123,0)..(123,65535)/). You can also use <cf/(123,5..100)/ for range
938
	  <cf/(123,5)..(123,100)/. You can also use <cf/*/ and <cf/a..b/ expressions
939
	  in the first part of a pair, note that such expressions are translated to a set
940
	  of intervals, which may be memory intensive. E.g. <cf/(*,4..20)/ is translated to
941
	  <cf/(0,4..20), (1,4..20), (2,4..20), ... (65535, 4..20)/.
942

    
943
	  EC sets use similar expressions like pair sets, e.g. <cf/(rt, 123, 10..20)/ 
944
	  or <cf/(ro, 123, *)/. Expressions requiring the translation (like  <cf/(rt, *, 3)/)
945
	  are not allowed (as they usually have 4B range for ASNs).
946

    
947
	  You can also use expressions for int, pair and EC set values. However it must
948
	  be possible to evaluate these expressions before daemon boots. So you can use
949
	  only constants inside them. E.g.
950
	<code>
951
	 define one=1;
952
	 define myas=64500;
953
	 int set odds;
954
	 pair set ps;
955
	 ec set es;
956

    
957
	 odds = [ one, 2+1, 6-one, 2*2*2-1, 9, 11 ];
958
	 ps = [ (1,one+one), (3,4)..(4,8), (5,*), (6,3..6), (7..9,*) ];
959
	 es = [ (rt, myas, 3*10), (rt, myas+one, 0..16*16*16-1), (ro, myas+2, *) ];
960
	</code>
961

    
962
	  Sets of prefixes are special: their literals does not allow ranges, but allows
963
	  prefix patterns that are written as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>.
964
	  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 
965
	  the first <cf>min(len1, len2)</cf> bits of <cf/ip1/ and <cf/ip2/ are identical and <cf>len1 &lt;= ip1 &lt;= len2</cf>.
966
	  A valid prefix pattern has to satisfy <cf>low &lt;= high</cf>, but <cf/pxlen/ is not constrained by <cf/low/
967
	  or <cf/high/. Obviously, a prefix matches a prefix set literal if it matches any prefix pattern in the
968
	  prefix set literal.
969

    
970
	  There are also two shorthands for prefix patterns: <cf><m>address</m>/<m/len/+</cf> is a shorthand for
971
	  <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), 
972
	  that means network prefix <cf><m>address</m>/<m/len/</cf> and all its subnets. <cf><m>address</m>/<m/len/-</cf>
973
	  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>
974
	  and all its supernets (network prefixes that contain it).
975

    
976
	  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
977
	  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
978
	  <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
979
	  IP address) whose prefix length is 20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP address
980
	  <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 &tilde; [ 1.0.0.0/8{15,17} ]</cf> is true,
981
	  but <cf>1.0.0.0/16 &tilde; [ 1.0.0.0/8- ]</cf> is false.
982

    
983
	  Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed
984
	  in BIRD as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as 
985
	  <cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as
986
	  <cf>192.168.0.0/16{24,32}</cf>.
987

    
988
	<tag/enum/
989
	  Enumeration types are fixed sets of possibilities. You can't define your own
990
	  variables of such type, but some route attributes are of enumeration
991
	  type. Enumeration types are incompatible with each other.
992

    
993
	<tag/bgppath/
994
	  BGP path is a list of autonomous system numbers. You can't write literals of this type.
995
	  There are several special operators on bgppaths:
996

    
997
	  <cf><m/P/.first</cf> returns the first ASN (the neighbor ASN) in path <m/P/.
998

    
999
          <cf><m/P/.last</cf> returns the last ASN (the source ASN) in path <m/P/.
1000

    
1001
	  Both <cf/first/ and <cf/last/ return zero if there is no appropriate ASN,
1002
          for example if the path contains an AS set element as the first (or the last) part.
1003

    
1004
          <cf><m/P/.len</cf> returns the length of path <m/P/.
1005

    
1006
          <cf>prepend(<m/P/,<m/A/)</cf> prepends ASN <m/A/ to path <m/P/ and returns the result.
1007
          Statement <cf><m/P/ = prepend(<m/P/, <m/A/);</cf> can be shortened to
1008
          <cf><m/P/.prepend(<m/A/);</cf> if <m/P/ is appropriate route attribute
1009
          (for example <cf/bgp_path/).
1010

    
1011
	<tag/bgpmask/
1012
	  BGP masks are patterns used for BGP path matching
1013
	  (using <cf>path &tilde; [= 2 3 5 * =]</cf> syntax). The masks
1014
	  resemble wildcard patterns as used by UNIX shells. Autonomous
1015
	  system numbers match themselves, <cf/*/ matches any (even empty)
1016
	  sequence of arbitrary AS numbers and <cf/?/ matches one arbitrary AS number.
1017
	  For example, if <cf>bgp_path</cf> is 4 3 2 1, then:
1018
	  <tt>bgp_path &tilde; [= * 4 3 * =]</tt> is true, but 
1019
	  <tt>bgp_path &tilde; [= * 4 5 * =]</tt> is false.
1020
	  BGP mask expressions can also contain integer expressions enclosed in parenthesis
1021
	  and integer variables, for example <tt>[= * 4 (1+2) a =]</tt>.
1022
	  There is also old syntax that uses / .. / instead of [= .. =] and ? instead of *.
1023

    
1024
	<tag/clist/
1025
	  Clist is similar to a set, except that unlike other sets, it
1026
	  can be modified. The type is used for community list (a set
1027
	  of pairs) and for cluster list (a set of quads). There exist
1028
	  no literals of this type. There are three special operators on
1029
	  clists:
1030

    
1031
          <cf>add(<m/C/,<m/P/)</cf> adds pair (or quad) <m/P/ to clist
1032
	  <m/C/ and returns the result.  If item <m/P/ is already in
1033
	  clist <m/C/, it does nothing. <m/P/ may also be a clist,
1034
	  in that case all its members are added; i.e., it works as clist union.
1035

    
1036
          <cf>delete(<m/C/,<m/P/)</cf> deletes pair (or quad)
1037
	  <m/P/ from clist <m/C/ and returns the result.  If clist
1038
	  <m/C/ does not contain item <m/P/, it does nothing.
1039
	  <m/P/ may also be a pair (or quad) set, in that case the
1040
	  operator deletes all items from clist <m/C/ that are also
1041
	  members of set <m/P/. Moreover, <m/P/ may also be a clist,
1042
	  which works analogously; i.e., it works as clist difference.
1043

    
1044
          <cf>filter(<m/C/,<m/P/)</cf> deletes all items from clist
1045
	  <m/C/ that are not members of pair (or quad) set <m/P/.
1046
	  I.e., <cf/filter/ do the same as <cf/delete/ with inverted
1047
	  set <m/P/. <m/P/ may also be a clist, which works analogously;
1048
	  i.e., it works as clist intersection.
1049

    
1050
          Statement <cf><m/C/ = add(<m/C/, <m/P/);</cf> can be shortened to
1051
          <cf><m/C/.add(<m/P/);</cf> if <m/C/ is appropriate route
1052
          attribute (for example <cf/bgp_community/). Similarly for
1053
          <cf/delete/ and <cf/filter/.
1054

    
1055
	<tag/eclist/
1056
	  Eclist is a data type used for BGP extended community lists.
1057
	  Eclists are very similar to clists, but they are sets of ECs
1058
	  instead of pairs. The same operations (like <cf/add/,
1059
	  <cf/delete/, or <cf/&tilde;/ membership operator) can be
1060
	  used to modify or test eclists, with ECs instead of pairs as
1061
	  arguments.
1062
</descrip>
1063

    
1064
<sect>Operators
1065

    
1066
<p>The filter language supports common integer operators <cf>(+,-,*,/)</cf>, parentheses <cf/(a*(b+c))/, comparison
1067
<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;/). 
1068
Special operators include <cf/&tilde;/ for "is element of a set" operation - it can be
1069
used on element and set of elements of the same type (returning true if element is contained in the given set), or
1070
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
1071
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).
1072

    
1073
<p>There is one operator related to ROA infrastructure -
1074
<cf/roa_check()/. It examines a ROA table and does RFC 6483 route
1075
origin validation for a given network prefix. The basic usage
1076
is <cf>roa_check(<m/table/)</cf>, which checks current route (which
1077
should be from BGP to have AS_PATH argument) in the specified ROA
1078
table and returns ROA_UNKNOWN if there is no relevant ROA, ROA_VALID
1079
if there is a matching ROA, or ROA_INVALID if there are some relevant
1080
ROAs but none of them match. There is also an extended variant
1081
<cf>roa_check(<m/table/, <m/prefix/, <m/asn/)</cf>, which allows to
1082
specify a prefix and an ASN as arguments.
1083

    
1084

    
1085
<sect>Control structures
1086

    
1087
<p>Filters support two control structures: conditions and case switches. 
1088

    
1089
<p>Syntax of a condition is: <cf>if
1090
<M>boolean expression</M> then <M>command1</M>; else <M>command2</M>;</cf> and you can use <cf>{
1091
<M>command_1</M>; <M>command_2</M>; <M>...</M> }</cf> instead of either command. The <cf>else</cf>
1092
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.
1093

    
1094
<p>The <cf>case</cf> is similar to case from Pascal. Syntax is <cf>case <m/expr/ { else: |
1095
<m/num_or_prefix [ .. num_or_prefix]/: <m/statement/ ; [ ... ] }</cf>. The expression after
1096
<cf>case</cf> can be of any type which can be on the left side of the &tilde; operator and anything that could
1097
be a member of a set is allowed before <cf/:/. Multiple commands are allowed without <cf/{}/ grouping.
1098
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.
1099

    
1100
<p>Here is example that uses <cf/if/ and <cf/case/ structures:
1101

    
1102
<code>
1103
case arg1 {
1104
	2: print "two"; print "I can do more commands without {}";
1105
	3 .. 5: print "three to five";
1106
	else: print "something else";
1107
}
1108

    
1109
if 1234 = i then printn "."; else { 
1110
  print "not 1234"; 
1111
  print "You need {} around multiple commands"; 
1112
}
1113
</code>
1114

    
1115
<sect>Route attributes
1116

    
1117
<p>A filter is implicitly passed a route, and it can access its
1118
attributes just like it accesses variables. Attempts to access undefined
1119
attribute result in a runtime error; you can check if an attribute is
1120
defined by using the <cf>defined( <m>attribute</m> )</cf> operator.
1121
One notable exception to this rule are attributes of clist type, where
1122
undefined value is regarded as empty clist for most purposes.
1123

    
1124
<descrip>
1125
	<tag><m/prefix/ net</tag>
1126
	Network the route is talking about. Read-only. (See the chapter about routing tables.)
1127

    
1128
	<tag><m/enum/ scope</tag>
1129
	The scope of the route. Possible values: <cf/SCOPE_HOST/ for
1130
	routes local to this host, <cf/SCOPE_LINK/ for those specific
1131
	for a physical link, <cf/SCOPE_SITE/ and
1132
	<cf/SCOPE_ORGANIZATION/ for private routes and
1133
	<cf/SCOPE_UNIVERSE/ for globally visible routes. This
1134
	attribute is not interpreted by BIRD and can be used to mark
1135
	routes in filters. The default value for new routes is
1136
	<cf/SCOPE_UNIVERSE/.
1137

    
1138
	<tag><m/int/ preference</tag>
1139
	Preference of the route. Valid values are 0-65535. (See the chapter about routing tables.)
1140

    
1141
	<tag><m/ip/ from</tag>
1142
	The router which the route has originated from. Read-only.
1143
	
1144
	<tag><m/ip/ gw</tag>
1145
	Next hop packets routed using this route should be forwarded to.
1146

    
1147
	<tag><m/string/ proto</tag>
1148
	The name of the protocol which the route has been imported from. Read-only.
1149

    
1150
	<tag><m/enum/ source</tag>
1151
	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/.
1152

    
1153
	<tag><m/enum/ cast</tag>
1154

    
1155
	Route type (Currently <cf/RTC_UNICAST/ for normal routes,
1156
	<cf/RTC_BROADCAST/, <cf/RTC_MULTICAST/, <cf/RTC_ANYCAST/ will
1157
	be used in the future for broadcast, multicast and anycast
1158
	routes). Read-only.
1159

    
1160
	<tag><m/enum/ dest</tag>
1161
	Type of destination the packets should be sent to
1162
	(<cf/RTD_ROUTER/ for forwarding to a neighboring router,
1163
	<cf/RTD_DEVICE/ for routing to a directly-connected network,
1164
	<cf/RTD_MULTIPATH/ for multipath destinations,
1165
	<cf/RTD_BLACKHOLE/ for packets to be silently discarded,
1166
	<cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that
1167
	should be returned with ICMP host unreachable / ICMP
1168
	administratively prohibited messages). Can be changed, but
1169
	only to <cf/RTD_BLACKHOLE/, <cf/RTD_UNREACHABLE/ or
1170
	<cf/RTD_PROHIBIT/.
1171

    
1172
	<tag><m/int/ igp_metric</tag>
1173
	The optional attribute that can be used to specify a distance
1174
	to the network for routes that do not have a native protocol
1175
	metric attribute (like <cf/ospf_metric1/ for OSPF routes). It
1176
	is used mainly by BGP to compare internal distances to boundary
1177
	routers (see below). It is also used when the route is exported
1178
	to OSPF as a default value for OSPF type 1 metric.
1179
</descrip>
1180

    
1181
<p>There also exist some protocol-specific attributes which are described in the corresponding protocol sections.
1182

    
1183
<sect>Other statements
1184

    
1185
<p>The following statements are available:
1186

    
1187
<descrip>
1188
	<tag><m/variable/ = <m/expr/</tag> Set variable to a given value.
1189

    
1190
	<tag>accept|reject [ <m/expr/ ]</tag> Accept or reject the route, possibly printing <cf><m>expr</m></cf>.
1191

    
1192
	<tag>return <m/expr/</tag> Return <cf><m>expr</m></cf> from the current function, the function ends at this point.
1193

    
1194
	<tag>print|printn <m/expr/ [<m/, expr.../]</tag>
1195
	Prints given expressions; useful mainly while debugging
1196
	filters. The <cf/printn/ variant does not terminate the line.
1197

    
1198
	<tag>quitbird</tag>
1199
	Terminates BIRD. Useful when debugging the filter interpreter.
1200
</descrip>
1201

    
1202
<chapt>Protocols
1203

    
1204
<sect>BGP
1205

    
1206
<p>The Border Gateway Protocol is the routing protocol used for backbone
1207
level routing in the today's Internet. Contrary to the other protocols, its convergence
1208
doesn't rely on all routers following the same rules for route selection,
1209
making it possible to implement any routing policy at any router in the
1210
network, the only restriction being that if a router advertises a route,
1211
it must accept and forward packets according to it.
1212

    
1213
<p>BGP works in terms of autonomous systems (often abbreviated as
1214
AS). Each AS is a part of the network with common management and
1215
common routing policy. It is identified by a unique 16-bit number
1216
(ASN).  Routers within each AS usually exchange AS-internal routing
1217
information with each other using an interior gateway protocol (IGP,
1218
such as OSPF or RIP). Boundary routers at the border of
1219
the AS communicate global (inter-AS) network reachability information with
1220
their neighbors in the neighboring AS'es via exterior BGP (eBGP) and
1221
redistribute received information to other routers in the AS via
1222
interior BGP (iBGP).
1223

    
1224
<p>Each BGP router sends to its neighbors updates of the parts of its
1225
routing table it wishes to export along with complete path information
1226
(a list of AS'es the packet will travel through if it uses the particular
1227
route) in order to avoid routing loops.
1228

    
1229
<p>BIRD supports all requirements of the BGP4 standard as defined in
1230
RFC 4271<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4271.txt">
1231
It also supports the community attributes
1232
(RFC 1997<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1997.txt">),
1233
capability negotiation
1234
(RFC 3392<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc3392.txt">),
1235
MD5 password authentication
1236
(RFC 2385<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2385.txt">),
1237
extended communities
1238
(RFC 4360<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4360.txt">),
1239
route reflectors 
1240
(RFC 4456<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4456.txt">),
1241
multiprotocol extensions
1242
(RFC 4760<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4760.txt">),
1243
4B AS numbers 
1244
(RFC 4893<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4893.txt">),
1245
and 4B AS numbers in extended communities
1246
(RFC 5668<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc5668.txt">).
1247

    
1248

    
1249
For IPv6, it uses the standard multiprotocol extensions defined in
1250
RFC 2283<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2283.txt">
1251
including changes described in the
1252
latest draft<htmlurl url="ftp://ftp.rfc-editor.org/internet-drafts/draft-ietf-idr-bgp4-multiprotocol-v2-05.txt">
1253
and applied to IPv6 according to
1254
RFC 2545<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2545.txt">.
1255

    
1256
<sect1>Route selection rules
1257

    
1258
<p>BGP doesn't have any simple metric, so the rules for selection of an optimal
1259
route among multiple BGP routes with the same preference are a bit more complex
1260
and they are implemented according to the following algorithm. It starts the first
1261
rule, if there are more "best" routes, then it uses the second rule to choose
1262
among them and so on.
1263

    
1264
<itemize>
1265
	<item>Prefer route with the highest Local Preference attribute.
1266
	<item>Prefer route with the shortest AS path.
1267
	<item>Prefer IGP origin over EGP and EGP origin over incomplete.
1268
	<item>Prefer the lowest value of the Multiple Exit Discriminator.
1269
	<item>Prefer routes received via eBGP over ones received via iBGP.
1270
	<item>Prefer routes with lower internal distance to a boundary router.
1271
	<item>Prefer the route with the lowest value of router ID of the
1272
	advertising router.
1273
</itemize>
1274

    
1275
<sect1>IGP routing table
1276

    
1277
<p>BGP is mainly concerned with global network reachability and with
1278
routes to other autonomous systems. When such routes are redistributed
1279
to routers in the AS via BGP, they contain IP addresses of a boundary
1280
routers (in route attribute NEXT_HOP). BGP depends on existing IGP
1281
routing table with AS-internal routes to determine immediate next hops
1282
for routes and to know their internal distances to boundary routers
1283
for the purpose of BGP route selection. In BIRD, there is usually
1284
one routing table used for both IGP routes and BGP routes.
1285

    
1286
<sect1>Configuration
1287

    
1288
<p>Each instance of the BGP corresponds to one neighboring router.
1289
This allows to set routing policy and all the other parameters differently
1290
for each neighbor using the following configuration parameters:
1291

    
1292
<descrip>
1293
	<tag>local [<m/ip/] as <m/number/</tag> Define which AS we
1294
	are part of. (Note that contrary to other IP routers, BIRD is
1295
	able to act as a router located in multiple AS'es
1296
	simultaneously, but in such cases you need to tweak the BGP
1297
	paths manually in the filters to get consistent behavior.)
1298
	Optional <cf/ip/ argument specifies a source address,
1299
	equivalent to the <cf/source address/ option (see below).
1300
	This parameter is mandatory.
1301

    
1302
	<tag>neighbor <m/ip/ as <m/number/</tag> Define neighboring router
1303
	this instance will be talking to and what AS it's located in. Unless
1304
	you use the <cf/multihop/ clause, it must be directly connected to one
1305
	of your router's interfaces. In case the neighbor is in the same AS
1306
	as we are, we automatically switch to iBGP. This parameter is mandatory.
1307

    
1308
	<tag>multihop [<m/number/]</tag> Configure multihop BGP
1309
	session to a neighbor that isn't directly connected.
1310
	Accurately, this option should be used if the configured
1311
	neighbor IP address does not match with any local network
1312
	subnets. Such IP address have to be reachable through system
1313
	routing table. For multihop BGP it is recommended to
1314
	explicitly configure <cf/source address/ to have it
1315
	stable. Optional <cf/number/ argument can be used to specify
1316
	the number of hops (used for TTL). Note that the number of
1317
	networks (edges) in a path is counted, i.e. if two BGP
1318
	speakers are separated by one router, the number of hops is
1319
	2. Default: switched off.
1320

    
1321
	<tag>source address <m/ip/</tag> Define local address we
1322
	should use for next hop calculation and as a source address
1323
	for the BGP session. Default: the address of the local
1324
	end of the interface our neighbor is connected to.
1325

    
1326
	<tag>next hop self</tag> Avoid calculation of the Next Hop
1327
	attribute and always advertise our own source address as a
1328
	next hop.  This needs to be used only occasionally to
1329
	circumvent misconfigurations of other routers.  Default:
1330
	disabled.
1331

    
1332
	<tag>next hop keep</tag> Forward the received Next Hop
1333
	attribute even in situations where the local address should be
1334
	used instead, like when the route is sent to an interface with
1335
	a different subnet. Default: disabled.
1336

    
1337
	<tag>missing lladdr self|drop|ignore</tag>Next Hop attribute
1338
	in BGP-IPv6 sometimes contains just the global IPv6 address,
1339
	but sometimes it has to contain both global and link-local
1340
	IPv6 addresses. This option specifies what to do if BIRD have
1341
	to send both addresses but does not know link-local address.
1342
	This situation might happen when routes from other protocols
1343
	are exported to BGP, or when improper updates are received
1344
	from BGP peers.  <cf/self/ means that BIRD advertises its own
1345
	local address instead. <cf/drop/ means that BIRD skips that
1346
	prefixes and logs error. <cf/ignore/ means that BIRD ignores
1347
	the problem and sends just the global address (and therefore
1348
	forms improper BGP update). Default: <cf/self/, unless BIRD
1349
	is configured as a route server (option <cf/rs client/), in
1350
	that case default is <cf/ignore/, because route servers usually
1351
	do not forward packets themselves.
1352

    
1353
	<tag>gateway direct|recursive</tag>For received routes, their
1354
	<cf/gw/ (immediate next hop) attribute is computed from
1355
	received <cf/bgp_next_hop/ attribute. This option specifies
1356
	how it is computed. Direct mode means that the IP address from
1357
	<cf/bgp_next_hop/ is used if it is directly reachable,
1358
	otherwise the neighbor IP address is used. Recursive mode
1359
	means that the gateway is computed by an IGP routing table
1360
	lookup for the IP address from <cf/bgp_next_hop/. Recursive
1361
	mode is the behavior specified by the BGP standard. Direct
1362
	mode is simpler, does not require any routes in a routing
1363
	table, and was used in older versions of BIRD, but does not
1364
	handle well nontrivial iBGP setups and multihop.  Recursive
1365
	mode is incompatible with <ref id="dsc-sorted" name="sorted
1366
	tables">. Default: <cf/direct/ for singlehop eBGP,
1367
	<cf/recursive/ otherwise.
1368

    
1369
	<tag>igp table <m/name/</tag> Specifies a table that is used
1370
	as an IGP routing table. Default: the same as the table BGP is
1371
	connected to.
1372
	
1373
	<tag>ttl security <m/switch/</tag> Use GTSM (RFC 5082 - the
1374
	generalized TTL security mechanism). GTSM protects against
1375
	spoofed packets by ignoring received packets with a smaller
1376
	than expected TTL. To work properly, GTSM have to be enabled
1377
	on both sides of a BGP session. If both <cf/ttl security/ and
1378
	<cf/multihop/ options are enabled, <cf/multihop/ option should
1379
	specify proper hop value to compute expected TTL. Kernel
1380
	support required: Linux: 2.6.34+ (IPv4), 2.6.35+ (IPv6), BSD:
1381
	since long ago, IPv4 only. Note that full (ICMP protection,
1382
	for example) RFC 5082 support is provided by Linux
1383
	only. Default: disabled.
1384
	
1385
	<tag>password <m/string/</tag> Use this password for MD5 authentication
1386
	of BGP sessions. Default: no authentication. Password has to be set by
1387
	external utility (e.g. setkey(8)) on BSD systems.
1388

    
1389
	<tag>passive <m/switch/</tag> Standard BGP behavior is both
1390
        initiating outgoing connections and accepting incoming
1391
        connections. In passive mode, outgoing connections are not
1392
        initiated. Default: off.
1393

    
1394
	<tag>rr client</tag> Be a route reflector and treat the neighbor as
1395
	a route reflection client. Default: disabled.
1396

    
1397
	<tag>rr cluster id <m/IPv4 address/</tag> Route reflectors use cluster id
1398
	to avoid route reflection loops. When there is one route reflector in a cluster
1399
	it usually uses its router id as a cluster id, but when there are more route
1400
	reflectors in a cluster, these need to be configured (using this option) to
1401
	use a common cluster id. Clients in a cluster need not know their cluster
1402
	id and this option is not allowed for them. Default: the same as router id.
1403

    
1404
	<tag>rs client</tag> Be a route server and treat the neighbor
1405
	as a route server client. A route server is used as a
1406
	replacement for full mesh EBGP routing in Internet exchange
1407
	points in a similar way to route reflectors used in IBGP routing.
1408
	BIRD does not implement obsoleted RFC 1863, but uses ad-hoc implementation,
1409
	which behaves like plain EBGP but reduces modifications to advertised route
1410
	attributes to be transparent (for example does not prepend its AS number to
1411
	AS PATH attribute and keeps MED attribute). Default: disabled.
1412

    
1413
	<tag>secondary <m/switch/</tag> Usually, if an import filter
1414
	rejects a selected route, no other route is propagated for
1415
	that network. This option allows to try the next route in
1416
	order until one that is accepted is found or all routes for
1417
	that network are rejected. This can be used for route servers
1418
	that need to propagate different tables to each client but do
1419
	not want to have these tables explicitly (to conserve memory).
1420
	This option requires that the connected routing table is
1421
	<ref id="dsc-sorted" name="sorted">. Default: off.
1422

    
1423
	<tag>enable route refresh <m/switch/</tag> When BGP speaker
1424
	changes its import filter, it has to re-examine all routes
1425
	received from its neighbor against the new filter. As these
1426
	routes might not be available, there is a BGP protocol
1427
	extension Route Refresh (specified in RFC 2918) that allows
1428
	BGP speaker to request re-advertisement of all routes from its
1429
	neighbor. This option specifies whether BIRD advertises this
1430
	capability and accepts such requests. Even when disabled, BIRD
1431
	can send route refresh requests. Default: on.
1432

    
1433
	<tag>interpret communities <m/switch/</tag> RFC 1997 demands
1434
	that BGP speaker should process well-known communities like
1435
	no-export (65535, 65281) or no-advertise (65535, 65282). For
1436
	example, received route carrying a no-adverise community
1437
	should not be advertised to any of its neighbors. If this
1438
	option is enabled (which is by default), BIRD has such
1439
	behavior automatically (it is evaluated when a route is
1440
	exported to the BGP protocol just before the export filter).
1441
	Otherwise, this integrated processing of well-known
1442
	communities is disabled. In that case, similar behavior can be
1443
	implemented in the export filter.  Default: on.
1444

    
1445
	<tag>enable as4 <m/switch/</tag> BGP protocol was designed to use 2B AS numbers
1446
	and was extended later to allow 4B AS number. BIRD supports 4B AS extension,
1447
	but by disabling this option it can be persuaded not to advertise it and
1448
	to maintain old-style sessions with its neighbors. This might be useful for
1449
	circumventing bugs in neighbor's implementation of 4B AS extension.
1450
	Even when disabled (off), BIRD behaves internally as AS4-aware BGP router.
1451
	Default: on.
1452

    
1453
	<tag>capabilities <m/switch/</tag> Use capability advertisement
1454
	to advertise optional capabilities. This is standard behavior
1455
	for newer BGP implementations, but there might be some older
1456
	BGP implementations that reject such connection attempts.
1457
	When disabled (off), features that request it (4B AS support)
1458
	are also disabled. Default: on, with automatic fallback to
1459
	off when received capability-related error.
1460

    
1461
	<tag>advertise ipv4 <m/switch/</tag> Advertise IPv4 multiprotocol capability.
1462
	This is not a correct behavior according to the strict interpretation
1463
	of RFC 4760, but it is widespread and required by some BGP
1464
	implementations (Cisco and Quagga). This option is relevant
1465
	to IPv4 mode with enabled capability advertisement only. Default: on.
1466

    
1467
	<tag>route limit <m/number/</tag> The maximal number of routes
1468
	that may be imported from the protocol. If the route limit is
1469
	exceeded, the connection is closed with error. Limit is currently implemented as
1470
	<cf/import limit number exceed restart/. Default: no limit.
1471

    
1472
	<tag>disable after error <m/switch/</tag> When an error is encountered (either
1473
	locally or by the other side), disable the instance automatically
1474
	and wait for an administrator to fix the problem manually. Default: off.
1475

    
1476
	<tag>hold time <m/number/</tag> Time in seconds to wait for a Keepalive
1477
	message from the other side before considering the connection stale.
1478
	Default: depends on agreement with the neighboring router, we prefer
1479
	240 seconds if the other side is willing to accept it.
1480

    
1481
	<tag>startup hold time <m/number/</tag> Value of the hold timer used
1482
	before the routers have a chance to exchange open messages and agree
1483
	on the real value. Default: 240 seconds.
1484

    
1485
	<tag>keepalive time <m/number/</tag> Delay in seconds between sending
1486
	of two consecutive Keepalive messages. Default: One third of the hold time.
1487

    
1488
	<tag>connect retry time <m/number/</tag> Time in seconds to wait before
1489
	retrying a failed attempt to connect. Default: 120 seconds.
1490

    
1491
	<tag>start delay time <m/number/</tag> Delay in seconds between protocol
1492
	startup and the first attempt to connect. Default: 5 seconds.
1493

    
1494
	<tag>error wait time <m/number/,<m/number/</tag> Minimum and maximum delay in seconds between a protocol
1495
	failure (either local or reported by the peer) and automatic restart.
1496
	Doesn't apply when <cf/disable after error/ is configured. If consecutive
1497
	errors happen, the delay is increased exponentially until it reaches the maximum. Default: 60, 300.
1498

    
1499
	<tag>error forget time <m/number/</tag> Maximum time in seconds between two protocol
1500
	failures to treat them as a error sequence which makes the <cf/error wait time/
1501
	increase exponentially. Default: 300 seconds.
1502

    
1503
	<tag>path metric <m/switch/</tag> Enable comparison of path lengths
1504
	when deciding which BGP route is the best one. Default: on.
1505

    
1506
	<tag>med metric <m/switch/</tag> Enable comparison of MED
1507
	attributes (during best route selection) even between routes
1508
	received from different ASes.  This may be useful if all MED
1509
	attributes contain some consistent metric, perhaps enforced in
1510
	import filters of AS boundary routers. If this option is
1511
	disabled, MED attributes are compared only if routes are
1512
	received from the same AS (which is the standard behavior).
1513
	Default: off.
1514

    
1515
	<tag>deterministic med <m/switch/</tag> BGP route selection
1516
	algorithm is often viewed as a comparison between individual
1517
	routes (e.g. if a new route appears and is better than the
1518
	current best one, it is chosen as the new best one). But the
1519
	proper route selection, as specified by RFC 4271, cannot be
1520
	fully implemented in that way. The problem is mainly in
1521
	handling the MED attribute. BIRD, by default, uses an
1522
	simplification based on individual route comparison, which in
1523
	some cases may lead to temporally dependent behavior (i.e. the
1524
	selection is dependent on the order in which routes appeared).
1525
	This option enables a different (and slower) algorithm
1526
	implementing proper RFC 4271 route selection, which is
1527
	deterministic. Alternative way how to get deterministic
1528
	behavior is to use <cf/med metric/ option. This option is
1529
	incompatible with <ref id="dsc-sorted" name="sorted tables">.
1530
	Default: off.
1531

    
1532
	<tag>igp metric <m/switch/</tag> Enable comparison of internal
1533
 	distances to boundary routers during best route selection. Default: on.
1534

    
1535
	<tag>prefer older <m/switch/</tag> Standard route selection algorithm
1536
	breaks ties by comparing router IDs. This changes the behavior
1537
	to prefer older routes (when both are external and from different
1538
	peer). For details, see RFC 5004. Default: off.
1539

    
1540
	<tag>default bgp_med <m/number/</tag> Value of the Multiple Exit
1541
	Discriminator to be used during route selection when the MED attribute
1542
	is missing. Default: 0.
1543

    
1544
	<tag>default bgp_local_pref <m/number/</tag> A default value
1545
	for the Local Preference attribute. It is used when a new
1546
	Local Preference attribute is attached to a route by the BGP
1547
	protocol itself (for example, if a route is received through
1548
	eBGP and therefore does not have such attribute). Default: 100
1549
	(0 in pre-1.2.0 versions of BIRD).
1550
</descrip>
1551

    
1552
<sect1>Attributes
1553

    
1554
<p>BGP defines several route attributes. Some of them (those marked with `<tt/I/' in the
1555
table below) are available on internal BGP connections only, some of them (marked
1556
with `<tt/O/') are optional.
1557

    
1558
<descrip>
1559
	<tag>bgppath <cf/bgp_path/</tag> Sequence of AS numbers describing the AS path
1560
	the packet will travel through when forwarded according to the particular route.
1561
	In case of internal BGP it doesn't contain the number of the local AS.
1562

    
1563
	<tag>int <cf/bgp_local_pref/ [I]</tag> Local preference value used for
1564
	selection among multiple BGP routes (see the selection rules above). It's
1565
	used as an additional metric which is propagated through the whole local AS.
1566

    
1567
	<tag>int <cf/bgp_med/ [O]</tag> The Multiple Exit Discriminator of the route
1568
	is an optional attribute which is used on external (inter-AS) links to
1569
	convey to an adjacent AS the optimal entry point into the local AS.
1570
	The received attribute is also propagated over internal BGP links.
1571
	The attribute value is zeroed when a route is exported to an external BGP
1572
	instance to ensure that the attribute received from a neighboring AS is
1573
	not propagated to other neighboring ASes. A new value might be set in
1574
	the export filter of an external BGP instance.
1575
	See RFC 4451<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4451.txt">
1576
	for further discussion of BGP MED attribute.
1577

    
1578
	<tag>enum <cf/bgp_origin/</tag> Origin of the route: either <cf/ORIGIN_IGP/
1579
	if the route has originated in an interior routing protocol or
1580
	<cf/ORIGIN_EGP/ if it's been imported from the <tt>EGP</tt> protocol
1581
	(nowadays it seems to be obsolete) or <cf/ORIGIN_INCOMPLETE/ if the origin
1582
	is unknown.
1583

    
1584
	<tag>ip <cf/bgp_next_hop/</tag> Next hop to be used for forwarding of packets
1585
	to this destination. On internal BGP connections, it's an address of the
1586
	originating router if it's inside the local AS or a boundary router the
1587
	packet will leave the AS through if it's an exterior route, so each BGP
1588
	speaker within the AS has a chance to use the shortest interior path
1589
	possible to this point.
1590

    
1591
	<tag>void <cf/bgp_atomic_aggr/ [O]</tag> This is an optional attribute
1592
	which carries no value, but the sole presence of which indicates that the route
1593
	has been aggregated from multiple routes by some router on the path from
1594
	the originator.
1595

    
1596
<!-- we don't handle aggregators right since they are of a very obscure type
1597
	<tag>bgp_aggregator</tag>
1598
-->
1599
	<tag>clist <cf/bgp_community/ [O]</tag> List of community values associated
1600
	with the route. Each such value is a pair (represented as a <cf/pair/ data
1601
	type inside the filters) of 16-bit integers, the first of them containing the number of the AS which defines
1602
	the community and the second one being a per-AS identifier. There are lots
1603
	of uses of the community mechanism, but generally they are used to carry
1604
	policy information like "don't export to USA peers". As each AS can define
1605
	its own routing policy, it also has a complete freedom about which community
1606
	attributes it defines and what will their semantics be.
1607

    
1608
	<tag>eclist <cf/bgp_ext_community/ [O]</tag> List of extended community
1609
	values associated with the route. Extended communities have similar usage
1610
	as plain communities, but they have an extended range (to allow 4B ASNs)
1611
	and a nontrivial structure with a type field. Individual community values are
1612
	represented using an <cf/ec/ data type inside the filters.
1613

    
1614
	<tag>quad <cf/bgp_originator_id/ [I, O]</tag> This attribute is created by the
1615
	route reflector when reflecting the route and contains the router ID of the
1616
	originator of the route in the local AS.
1617

    
1618
	<tag>clist <cf/bgp_cluster_list/ [I, O]</tag> This attribute contains a list
1619
	of cluster IDs of route reflectors. Each route reflector prepends its
1620
	cluster ID when reflecting the route.
1621
</descrip>
1622

    
1623
<sect1>Example
1624

    
1625
<p><code>
1626
protocol bgp {
1627
	local as 65000;			     # Use a private AS number
1628
	neighbor 198.51.100.130 as 64496;    # Our neighbor ...
1629
	multihop;			     # ... which is connected indirectly
1630
	export filter {			     # We use non-trivial export rules
1631
		if source = RTS_STATIC then { # Export only static routes
1632
		        # Assign our community
1633
			bgp_community.add((65000,64501));
1634
			# Artificially increase path length
1635
			# by advertising local AS number twice
1636
			if bgp_path ~ [= 65000 =] then
1637
				bgp_path.prepend(65000);
1638
			accept;
1639
		}
1640
		reject;
1641
	};
1642
	import all;
1643
	source address 198.51.100.14;	# Use a non-standard source address
1644
}
1645
</code>
1646

    
1647
<sect>Device
1648

    
1649
<p>The Device protocol is not a real routing protocol.  It doesn't generate
1650
any routes and it only serves as a module for getting information about network
1651
interfaces from the kernel.
1652

    
1653
<p>Except for very unusual circumstances, you probably should include
1654
this protocol in the configuration since almost all other protocols
1655
require network interfaces to be defined for them to work with.
1656

    
1657
<sect1>Configuration
1658

    
1659
<p><descrip>
1660
	<tag>scan time <m/number/</tag> Time in seconds between two scans
1661
	of the network interface list. On systems where we are notified about
1662
	interface status changes asynchronously (such as newer versions of
1663
	Linux), we need to scan the list only in order to avoid confusion by lost
1664
	notification messages, so the default time is set to a large value.
1665

    
1666
	<tag>primary  [ "<m/mask/" ] <m/prefix/</tag>
1667
	If a network interface has more than one network address, BIRD
1668
	has to choose one of them as a primary one. By default, BIRD
1669
	chooses the lexicographically smallest address as the primary
1670
	one.
1671

    
1672
	This option allows to specify which network address should be
1673
	chosen as a primary one. Network addresses that match
1674
	<m/prefix/ are preferred to non-matching addresses. If more
1675
	<cf/primary/ options are used, the first one has the highest
1676
	preference. If "<m/mask/" is specified, then such
1677
	<cf/primary/ option is relevant only to matching network
1678
	interfaces.
1679

    
1680
	In all cases, an address marked by operating system as
1681
	secondary cannot be chosen as the primary one. 
1682
</descrip>
1683

    
1684
<p>As the Device protocol doesn't generate any routes, it cannot have
1685
any attributes. Example configuration looks like this:
1686

    
1687
<p><code>
1688
protocol device {
1689
	scan time 10;		# Scan the interfaces often
1690
	primary "eth0" 192.168.1.1;
1691
	primary 192.168.0.0/16;
1692
}
1693
</code>
1694

    
1695
<sect>Direct
1696

    
1697
<p>The Direct protocol is a simple generator of device routes for all the
1698
directly connected networks according to the list of interfaces provided
1699
by the kernel via the Device protocol.
1700

    
1701
<p>The question is whether it is a good idea to have such device
1702
routes in BIRD routing table. OS kernel usually handles device routes
1703
for directly connected networks by itself so we don't need (and don't
1704
want) to export these routes to the kernel protocol. OSPF protocol
1705
creates device routes for its interfaces itself and BGP protocol is
1706
usually used for exporting aggregate routes. Although there are some
1707
use cases that use the direct protocol (like abusing eBGP as an IGP
1708
routing protocol), in most cases it is not needed to have these device
1709
routes in BIRD routing table and to use the direct protocol.
1710

    
1711
<p>There is one notable case when you definitely want to use the
1712
direct protocol -- running BIRD on BSD systems. Having high priority
1713
device routes for directly connected networks from the direct protocol
1714
protects kernel device routes from being overwritten or removed by IGP
1715
routes during some transient network conditions, because a lower
1716
priority IGP route for the same network is not exported to the kernel
1717
routing table. This is an issue on BSD systems only, as on Linux
1718
systems BIRD cannot change non-BIRD route in the kernel routing table.
1719

    
1720
<p>The only configurable thing about direct is what interfaces it watches:
1721

    
1722
<p><descrip>
1723
	<tag>interface <m/pattern [, ...]/</tag> By default, the Direct
1724
	protocol will generate device routes for all the interfaces
1725
	available. If you want to restrict it to some subset of interfaces
1726
	(for example if you're using multiple routing tables for policy
1727
	routing and some of the policy domains don't contain all interfaces),
1728
	just use this clause.
1729
</descrip>
1730

    
1731
<p>Direct device routes don't contain any specific attributes.
1732

    
1733
<p>Example config might look like this:
1734

    
1735
<p><code>
1736
protocol direct {
1737
	interface "-arc*", "*";		# Exclude the ARCnets
1738
}
1739
</code>
1740

    
1741
<sect>Kernel
1742

    
1743
<p>The Kernel protocol is not a real routing protocol. Instead of communicating
1744
with other routers in the network, it performs synchronization of BIRD's routing
1745
tables with the OS kernel. Basically, it sends all routing table updates to the kernel
1746
and from time to time it scans the kernel tables to see whether some routes have
1747
disappeared (for example due to unnoticed up/down transition of an interface)
1748
or whether an `alien' route has been added by someone else (depending on the
1749
<cf/learn/ switch, such routes are either ignored or accepted to our
1750
table).
1751

    
1752
<p>Unfortunately, there is one thing that makes the routing table
1753
synchronization a bit more complicated. In the kernel routing table
1754
there are also device routes for directly connected networks. These
1755
routes are usually managed by OS itself (as a part of IP address
1756
configuration) and we don't want to touch that.  They are completely
1757
ignored during the scan of the kernel tables and also the export of
1758
device routes from BIRD tables to kernel routing tables is restricted
1759
to prevent accidental interference. This restriction can be disabled using
1760
<cf/device routes/ switch.
1761

    
1762
<p>If your OS supports only a single routing table, you can configure
1763
only one instance of the Kernel protocol. If it supports multiple
1764
tables (in order to allow policy routing; such an OS is for example
1765
Linux), you can run as many instances as you want, but each of them
1766
must be connected to a different BIRD routing table and to a different
1767
kernel table.
1768

    
1769
<p>Because the kernel protocol is partially integrated with the
1770
connected routing table, there are two limitations - it is not
1771
possible to connect more kernel protocols to the same routing table
1772
and changing route destination/gateway in an export
1773
filter of a kernel protocol does not work. Both limitations can be
1774
overcome using another routing table and the pipe protocol.
1775

    
1776
<sect1>Configuration
1777

    
1778
<p><descrip>
1779
	<tag>persist <m/switch/</tag> Tell BIRD to leave all its routes in the
1780
	routing tables when it exits (instead of cleaning them up).
1781
	<tag>scan time <m/number/</tag> Time in seconds between two consecutive scans of the
1782
	kernel routing table.
1783
	<tag>learn <m/switch/</tag> Enable learning of routes added to the kernel
1784
	routing tables by other routing daemons or by the system administrator.
1785
	This is possible only on systems which support identification of route
1786
	authorship.
1787

    
1788
	<tag>device routes <m/switch/</tag> Enable export of device
1789
	routes to the kernel routing table. By default, such routes
1790
	are rejected (with the exception of explicitly configured
1791
	device routes from the static protocol) regardless of the
1792
	export filter to protect device routes in kernel routing table
1793
	(managed by OS itself) from accidental overwriting or erasing.
1794

    
1795
	<tag>kernel table <m/number/</tag> Select which kernel table should
1796
	this particular instance of the Kernel protocol work with. Available
1797
	only on systems supporting multiple routing tables.
1798
</descrip>
1799

    
1800
<sect1>Attributes
1801

    
1802
<p>The Kernel protocol defines several attributes. These attributes
1803
are translated to appropriate system (and OS-specific) route attributes.
1804
We support these attributes:
1805

    
1806
<descrip>
1807
	<tag>int <cf/krt_source/</tag> The original source of the imported
1808
	kernel route.  The value is system-dependent. On Linux, it is
1809
	a value of the protocol field of the route. See
1810
	/etc/iproute2/rt_protos for common values.  On BSD, it is
1811
	based on STATIC and PROTOx flags. The attribute is read-only.
1812

    
1813
	<tag>int <cf/krt_metric/</tag> The kernel metric of
1814
	the route.  When multiple same routes are in a kernel routing
1815
	table, the Linux kernel chooses one with lower metric.
1816

    
1817
	<tag>ip <cf/krt_prefsrc/</tag> (Linux) The preferred source address.
1818
 	Used in source address selection for outgoing packets. Have to
1819
 	be one of IP addresses of the router.
1820

    
1821
	<tag>int <cf/krt_realm/</tag> (Linux) The realm of the route. Can be
1822
	used for traffic classification.
1823
</descrip>
1824

    
1825
<sect1>Example
1826

    
1827
<p>A simple configuration can look this way:
1828

    
1829
<p><code>
1830
protocol kernel {
1831
	export all;
1832
}
1833
</code>
1834

    
1835
<p>Or for a system with two routing tables:
1836

    
1837
<p><code>
1838
protocol kernel {		# Primary routing table
1839
	learn;			# Learn alien routes from the kernel
1840
	persist;		# Don't remove routes on bird shutdown
1841
	scan time 10;		# Scan kernel routing table every 10 seconds
1842
	import all;
1843
	export all;
1844
}
1845

    
1846
protocol kernel {		# Secondary routing table
1847
	table auxtable;
1848
	kernel table 100;
1849
	export all;
1850
}
1851
</code>
1852

    
1853
<sect>OSPF
1854

    
1855
<sect1>Introduction
1856

    
1857
<p>Open Shortest Path First (OSPF) is a quite complex interior gateway
1858
protocol. The current IPv4 version (OSPFv2) is defined in RFC
1859
2328<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2328.txt"> and
1860
the current IPv6 version (OSPFv3) is defined in RFC 5340<htmlurl
1861
url="ftp://ftp.rfc-editor.org/in-notes/rfc5340.txt">  It's a link state
1862
(a.k.a. shortest path first) protocol -- each router maintains a
1863
database describing the autonomous system's topology. Each participating
1864
router has an identical copy of the database and all routers run the
1865
same algorithm calculating a shortest path tree with themselves as a
1866
root. OSPF chooses the least cost path as the best path.
1867

    
1868
<p>In OSPF, the autonomous system can be split to several areas in order
1869
to reduce the amount of resources consumed for exchanging the routing
1870
information and to protect the other areas from incorrect routing data.
1871
Topology of the area is hidden to the rest of the autonomous system.
1872

    
1873
<p>Another very important feature of OSPF is that
1874
it can keep routing information from other protocols (like Static or BGP)
1875
in its link state database as external routes. Each external route can
1876
be tagged by the advertising router, making it possible to pass additional
1877
information between routers on the boundary of the autonomous system.
1878

    
1879
<p>OSPF quickly detects topological changes in the autonomous system (such
1880
as router interface failures) and calculates new loop-free routes after a short
1881
period of convergence. Only a minimal amount of 
1882
routing traffic is involved.
1883

    
1884
<p>Each router participating in OSPF routing periodically sends Hello messages
1885
to all its interfaces. This allows neighbors to be discovered dynamically.
1886
Then the neighbors exchange theirs parts of the link state database and keep it
1887
identical by flooding updates. The flooding process is reliable and ensures
1888
that each router detects all changes.
1889

    
1890
<sect1>Configuration
1891

    
1892
<p>In the main part of configuration, there can be multiple definitions of
1893
OSPF areas, each with a different id. These definitions includes many other
1894
switches and multiple definitions of interfaces. Definition of interface
1895
may contain many switches and constant definitions and list of neighbors
1896
on nonbroadcast networks.
1897

    
1898
<code>
1899
protocol ospf &lt;name&gt; {
1900
	rfc1583compat &lt;switch&gt;;
1901
	tick &lt;num&gt;;
1902
	ecmp &lt;switch&gt; [limit &lt;num&gt;];
1903
	area &lt;id&gt; {
1904
		stub;
1905
		nssa;
1906
		summary &lt;switch&gt;;
1907
		default nssa &lt;switch&gt;;
1908
		default cost &lt;num&gt;;
1909
		default cost2 &lt;num&gt;;
1910
		translator &lt;switch&gt;;
1911
		translator stability &lt;num&gt;;
1912

    
1913
                networks {
1914
			&lt;prefix&gt;;
1915
			&lt;prefix&gt; hidden;
1916
		}
1917
                external {
1918
			&lt;prefix&gt;;
1919
			&lt;prefix&gt; hidden;
1920
			&lt;prefix&gt; tag &lt;num&gt;;
1921
		}
1922
		stubnet &lt;prefix&gt;;
1923
		stubnet &lt;prefix&gt; {
1924
			hidden &lt;switch&gt;;
1925
			summary &lt;switch&gt;;
1926
			cost &lt;num&gt;;
1927
		}
1928
		interface &lt;interface pattern&gt; [instance &lt;num&gt;] {
1929
			cost &lt;num&gt;;
1930
			stub &lt;switch&gt;;
1931
			hello &lt;num&gt;;
1932
			poll &lt;num&gt;;
1933
			retransmit &lt;num&gt;;
1934
			priority &lt;num&gt;;
1935
			wait &lt;num&gt;;
1936
			dead count &lt;num&gt;;
1937
			dead &lt;num&gt;;
1938
			rx buffer [normal|large|&lt;num&gt;];
1939
			type [broadcast|bcast|pointopoint|ptp|
1940
				nonbroadcast|nbma|pointomultipoint|ptmp];
1941
			strict nonbroadcast &lt;switch&gt;;
1942
			real broadcast &lt;switch&gt;;
1943
			ptp netmask &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>ptp netmask <m/switch/</tag>
2188
	 In <cf/type ptp/ network configurations, OSPFv2
2189
	 implementations should ignore received netmask field in hello
2190
	 packets and should send hello packets with zero netmask field
2191
	 on unnumbered PtP links. But some OSPFv2 implementations
2192
	 perform netmask checking even for PtP links. This option
2193
	 specifies whether real netmask will be used in hello packets
2194
	 on <cf/type ptp/ interfaces. You should ignore this option
2195
	 unless you meet some compatibility problems related to this
2196
	 issue. Default value is no for unnumbered PtP links, yes
2197
	 otherwise.
2198

    
2199
	<tag>check link <M>switch</M></tag>
2200
	 If set, a hardware link state (reported by OS) is taken into
2201
	 consideration. When a link disappears (e.g. an ethernet cable is
2202
	 unplugged), neighbors are immediately considered unreachable
2203
	 and only the address of the iface (instead of whole network
2204
	 prefix) is propagated. It is possible that some hardware
2205
	 drivers or platforms do not implement this feature. Default value is no.
2206

    
2207
	<tag>ecmp weight <M>num</M></tag>
2208
	 When ECMP (multipath) routes are allowed, this value specifies
2209
	 a relative weight used for nexthops going through the iface.
2210
	 Allowed values are 1-256. Default value is 1.
2211

    
2212
	<tag>authentication none</tag>
2213
	 No passwords are sent in OSPF packets. This is the default value.
2214

    
2215
	<tag>authentication simple</tag>
2216
	 Every packet carries 8 bytes of password. Received packets
2217
	 lacking this password are ignored. This authentication mechanism is
2218
	 very weak.
2219

    
2220
	<tag>authentication cryptographic</tag>
2221
	 16-byte long MD5 digest is appended to every packet. For the digest
2222
         generation 16-byte long passwords are used. Those passwords are 
2223
         not sent via network, so this mechanism is quite secure.
2224
         Packets can still be read by an attacker.
2225

    
2226
	<tag>password "<M>text</M>"</tag>
2227
	 An 8-byte or 16-byte password used for authentication.
2228
	 See <ref id="dsc-pass" name="password"> common option for detailed description.
2229

    
2230
	<tag>neighbors { <m/set/ } </tag>
2231
	 A set of neighbors to which Hello messages on NBMA or PtMP
2232
	 networks are to be sent. For NBMA networks, some of them
2233
	 could be marked as eligible. In OSPFv3, link-local addresses
2234
	 should be used, using global ones is possible, but it is
2235
	 nonstandard and might be problematic. And definitely,
2236
	 link-local and global addresses should not be mixed.
2237

    
2238
</descrip>
2239

    
2240
<sect1>Attributes
2241

    
2242
<p>OSPF defines four route attributes. Each internal route has a <cf/metric/.
2243
Metric is ranging from 1 to infinity (65535).
2244
External routes use <cf/metric type 1/ or <cf/metric type 2/.
2245
A <cf/metric of type 1/ is comparable with internal <cf/metric/, a
2246
<cf/metric of type 2/ is always longer
2247
than any <cf/metric of type 1/ or any <cf/internal metric/.
2248
<cf/Internal metric/ or <cf/metric of type 1/ is stored in attribute
2249
<cf/ospf_metric1/, <cf/metric type 2/ is stored in attribute <cf/ospf_metric2/.
2250
If you specify both metrics only metric1 is used.
2251

    
2252
Each external route can also carry attribute <cf/ospf_tag/ which is a
2253
32-bit integer which is used when exporting routes to other protocols;
2254
otherwise, it doesn't affect routing inside the OSPF domain at all.
2255
The fourth attribute <cf/ospf_router_id/ is a router ID of the router
2256
advertising that route/network. This attribute is read-only. Default
2257
is <cf/ospf_metric2 = 10000/ and <cf/ospf_tag = 0/.
2258

    
2259
<sect1>Example
2260

    
2261
<p>
2262

    
2263
<code>
2264
protocol ospf MyOSPF {
2265
        rfc1583compat yes;
2266
        tick 2;
2267
	export filter {
2268
		if source = RTS_BGP then {
2269
			ospf_metric1 = 100;
2270
			accept;
2271
		}
2272
		reject;
2273
	};
2274
	area 0.0.0.0 {
2275
		interface "eth*" {
2276
			cost 11;
2277
			hello 15;
2278
			priority 100;
2279
			retransmit 7;
2280
			authentication simple;
2281
			password "aaa";
2282
		};
2283
		interface "ppp*" {
2284
			cost 100;
2285
			authentication cryptographic;
2286
			password "abc" {
2287
				id 1;
2288
				generate to "22-04-2003 11:00:06";
2289
				accept from "17-01-2001 12:01:05";
2290
			};
2291
			password "def" {
2292
				id 2;
2293
				generate to "22-07-2005 17:03:21";
2294
				accept from "22-02-2001 11:34:06";
2295
			};
2296
		};
2297
		interface "arc0" {
2298
			cost 10;
2299
			stub yes;
2300
		};
2301
		interface "arc1";
2302
	};
2303
	area 120 {
2304
		stub yes;
2305
		networks {
2306
			172.16.1.0/24;
2307
			172.16.2.0/24 hidden;
2308
		}
2309
		interface "-arc0" , "arc*" {
2310
			type nonbroadcast;
2311
			authentication none;
2312
			strict nonbroadcast yes;
2313
			wait 120;
2314
			poll 40;
2315
			dead count 8;
2316
			neighbors {
2317
				192.168.120.1 eligible;
2318
				192.168.120.2;
2319
				192.168.120.10;
2320
			};
2321
		};
2322
	};
2323
}
2324
</code>
2325

    
2326
<sect>Pipe
2327

    
2328
<sect1>Introduction
2329

    
2330
<p>The Pipe protocol serves as a link between two routing tables, allowing routes to be
2331
passed from a table declared as primary (i.e., the one the pipe is connected to using the
2332
<cf/table/ configuration keyword) to the secondary one (declared using <cf/peer table/)
2333
and vice versa, depending on what's allowed by the filters. Export filters control export
2334
of routes from the primary table to the secondary one, import filters control the opposite
2335
direction.
2336

    
2337
<p>The Pipe protocol may work in the transparent mode mode or in the opaque mode.
2338
In the transparent mode, the Pipe protocol retransmits all routes from
2339
one table to the other table, retaining their original source and
2340
attributes.  If import and export filters are set to accept, then both
2341
tables would have the same content. The transparent mode is the default mode.
2342

    
2343
<p>In the opaque mode, the Pipe protocol retransmits optimal route
2344
from one table to the other table in a similar way like other
2345
protocols send and receive routes. Retransmitted route will have the
2346
source set to the Pipe protocol, which may limit access to protocol
2347
specific route attributes. This mode is mainly for compatibility, it
2348
is not suggested for new configs. The mode can be changed by
2349
<tt/mode/ option.
2350

    
2351
<p>The primary use of multiple routing tables and the Pipe protocol is for policy routing,
2352
where handling of a single packet doesn't depend only on its destination address, but also
2353
on its source address, source interface, protocol type and other similar parameters.
2354
In many systems (Linux being a good example), the kernel allows to enforce routing policies
2355
by defining routing rules which choose one of several routing tables to be used for a packet
2356
according to its parameters. Setting of these rules is outside the scope of BIRD's work
2357
(on Linux, you can use the <tt/ip/ command), but you can create several routing tables in BIRD,
2358
connect them to the kernel ones, use filters to control which routes appear in which tables
2359
and also you can employ the Pipe protocol for exporting a selected subset of one table to
2360
another one.
2361

    
2362
<sect1>Configuration
2363

    
2364
<p><descrip>
2365
	<tag>peer table <m/table/</tag> Defines secondary routing table to connect to. The
2366
	primary one is selected by the <cf/table/ keyword.
2367

    
2368
	<tag>mode opaque|transparent</tag> Specifies the mode for the pipe to work in. Default is opaque.
2369
</descrip>
2370

    
2371
<sect1>Attributes
2372

    
2373
<p>The Pipe protocol doesn't define any route attributes.
2374

    
2375
<sect1>Example
2376

    
2377
<p>Let's consider a router which serves as a boundary router of two different autonomous
2378
systems, each of them connected to a subset of interfaces of the router, having its own
2379
exterior connectivity and wishing to use the other AS as a backup connectivity in case
2380
of outage of its own exterior line.
2381

    
2382
<p>Probably the simplest solution to this situation is to use two routing tables (we'll
2383
call them <cf/as1/ and <cf/as2/) and set up kernel routing rules, so that packets having
2384
arrived from interfaces belonging to the first AS will be routed according to <cf/as1/
2385
and similarly for the second AS. Thus we have split our router to two logical routers,
2386
each one acting on its own routing table, having its own routing protocols on its own
2387
interfaces. In order to use the other AS's routes for backup purposes, we can pass
2388
the routes between the tables through a Pipe protocol while decreasing their preferences
2389
and correcting their BGP paths to reflect the AS boundary crossing.
2390

    
2391
<code>
2392
table as1;				# Define the tables
2393
table as2;
2394

    
2395
protocol kernel kern1 {			# Synchronize them with the kernel
2396
	table as1;
2397
	kernel table 1;
2398
}
2399

    
2400
protocol kernel kern2 {
2401
	table as2;
2402
	kernel table 2;
2403
}
2404

    
2405
protocol bgp bgp1 {			# The outside connections
2406
	table as1;
2407
	local as 1;
2408
	neighbor 192.168.0.1 as 1001;
2409
	export all;
2410
	import all;
2411
}
2412

    
2413
protocol bgp bgp2 {
2414
	table as2;
2415
	local as 2;
2416
	neighbor 10.0.0.1 as 1002;
2417
	export all;
2418
	import all;
2419
}
2420

    
2421
protocol pipe {				# The Pipe
2422
	table as1;
2423
	peer table as2;
2424
	export filter {
2425
		if net ~ [ 1.0.0.0/8+] then {	# Only AS1 networks
2426
			if preference>10 then preference = preference-10;
2427
			if source=RTS_BGP then bgp_path.prepend(1);
2428
			accept;
2429
		}
2430
		reject;
2431
	};
2432
	import filter {
2433
		if net ~ [ 2.0.0.0/8+] then {	# Only AS2 networks
2434
			if preference>10 then preference = preference-10;
2435
			if source=RTS_BGP then bgp_path.prepend(2);
2436
			accept;
2437
		}
2438
		reject;
2439
	};
2440
}
2441
</code>
2442

    
2443
<sect>RAdv
2444

    
2445
<sect1>Introduction
2446

    
2447
<p>The RAdv protocol is an implementation of Router Advertisements,
2448
which are used in the IPv6 stateless autoconfiguration. IPv6 routers
2449
send (in irregular time intervals or as an answer to a request)
2450
advertisement packets to connected networks. These packets contain
2451
basic information about a local network (e.g. a list of network
2452
prefixes), which allows network hosts to autoconfigure network
2453
addresses and choose a default route. BIRD implements router behavior
2454
as defined in
2455
RFC 4861<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc4861.txt">
2456
and also the DNS extensions from
2457
RFC 6106<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc6106.txt">.
2458

    
2459
<sect1>Configuration
2460

    
2461
<p>There are several classes of definitions in RAdv configuration --
2462
interface definitions, prefix definitions and DNS definitions:
2463

    
2464
<descrip>
2465
	<tag>interface <m/pattern [, ...]/  { <m/options/ }</tag>
2466
	Interface definitions specify a set of interfaces on which the
2467
	protocol is activated and contain interface specific options.
2468
	See <ref id="dsc-iface" name="interface"> common options for
2469
	detailed description.
2470

    
2471
	<tag>prefix <m/prefix/ { <m/options/ }</tag>
2472
	Prefix definitions allow to modify a list of advertised
2473
	prefixes. By default, the advertised prefixes are the same as
2474
	the network prefixes assigned to the interface. For each
2475
	network prefix, the matching prefix definition is found and
2476
	its options are used. If no matching prefix definition is
2477
	found, the prefix is used with default options.
2478

    
2479
	Prefix definitions can be either global or interface-specific.
2480
	The second ones are part of interface options. The prefix
2481
	definition matching is done in the first-match style, when
2482
	interface-specific definitions are processed before global
2483
	definitions. As expected, the prefix definition is matching if
2484
	the network prefix is a subnet of the prefix in prefix
2485
	definition.
2486

    
2487
	<tag>rdnss { <m/options/ }</tag>
2488
	RDNSS definitions allow to specify a list of advertised
2489
	recursive DNS servers together with their options. As options
2490
	are seldom necessary, there is also a short variant <cf>rdnss
2491
	<m/address/</cf> that just specifies one DNS server. Multiple
2492
	definitions are cumulative. RDNSS definitions may also be
2493
	interface-specific when used inside interface options. By
2494
	default, interface uses both global and interface-specific
2495
	options, but that can be changed by <cf/rdnss local/ option.
2496

    
2497
	<tag>dnssl { <m/options/ }</tag>
2498
	DNSSL definitions allow to specify a list of advertised DNS
2499
	search domains together with their options. Like <cf/rdnss/
2500
	above, multiple definitions are cumulative, they can be used
2501
	also as interface-specific options and there is a short
2502
	variant <cf>dnssl <m/domain/</cf> that just specifies one DNS
2503
        search domain.
2504

    
2505
	<label id="dsc-trigger"> <tag>trigger <m/prefix/</tag>
2506
	RAdv protocol could be configured to change its behavior based
2507
	on availability of routes. When this option is used, the
2508
	protocol waits in suppressed state until a <it/trigger route/
2509
	(for the specified network) is exported to the protocol, the
2510
	protocol also returnsd to suppressed state if the
2511
	<it/trigger route/ disappears. Note that route export depends
2512
	on specified export filter, as usual. This option could be
2513
	used, e.g., for handling failover in multihoming scenarios.
2514

    
2515
	During suppressed state, router advertisements are generated,
2516
	but with some fields zeroed. Exact behavior depends on which
2517
	fields are zeroed, this can be configured by
2518
	<cf/sensitive/ option for appropriate fields. By default, just
2519
	<cf/default lifetime/ (also called <cf/router lifetime/) is
2520
	zeroed, which means hosts cannot use the router as a default
2521
	router. <cf/preferred lifetime/ and <cf/valid lifetime/ could
2522
	also be configured as <cf/sensitive/ for a prefix, which would
2523
	cause autoconfigured IPs to be deprecated or even removed.
2524
</descrip>
2525

    
2526
<p>Interface specific options:
2527

    
2528
<descrip>
2529
	<tag>max ra interval <m/expr/</tag>
2530
	Unsolicited router advertisements are sent in irregular time
2531
	intervals. This option specifies the maximum length of these
2532
	intervals, in seconds. Valid values are 4-1800. Default: 600
2533

    
2534
	<tag>min ra interval <m/expr/</tag>
2535
	This option specifies the minimum length of that intervals, in
2536
	seconds. Must be at least 3 and at most 3/4 * <cf/max ra interval/.
2537
	Default: about 1/3 * <cf/max ra interval/.
2538

    
2539
	<tag>min delay <m/expr/</tag>
2540
	The minimum delay between two consecutive router advertisements,
2541
	in seconds. Default: 3
2542

    
2543
	<tag>managed <m/switch/</tag>
2544
	This option specifies whether hosts should use DHCPv6 for
2545
	IP address configuration. Default: no
2546

    
2547
	<tag>other config <m/switch/</tag>
2548
	This option specifies whether hosts should use DHCPv6 to
2549
	receive other configuration information. Default: no
2550

    
2551
	<tag>link mtu <m/expr/</tag>
2552
	This option specifies which value of MTU should be used by
2553
	hosts. 0 means unspecified. Default: 0
2554

    
2555
	<tag>reachable time <m/expr/</tag>
2556
	This option specifies the time (in milliseconds) how long
2557
	hosts should assume a neighbor is reachable (from the last
2558
	confirmation). Maximum is 3600000, 0 means unspecified.
2559
	Default 0.
2560

    
2561
	<tag>retrans timer <m/expr/</tag>
2562
	This option specifies the time (in milliseconds) how long
2563
	hosts should wait before retransmitting Neighbor Solicitation
2564
	messages. 0 means unspecified. Default 0.
2565

    
2566
	<tag>current hop limit <m/expr/</tag>
2567
	This option specifies which value of Hop Limit should be used
2568
	by hosts. Valid values are 0-255, 0 means unspecified. Default: 64
2569

    
2570
	<tag>default lifetime <m/expr/ [sensitive <m/switch/]</tag>
2571
	This option specifies the time (in seconds) how long (after
2572
	the receipt of RA) hosts may use the router as a default
2573
	router. 0 means do not use as a default router. For
2574
	<cf/sensitive/ option, see <ref id="dsc-trigger" name="trigger">.
2575
	Default: 3 * <cf/max ra interval/, <cf/sensitive/ yes.
2576

    
2577
	<tag>rdnss local <m/switch/</tag>
2578
	Use only local (interface-specific) RDNSS definitions for this
2579
	interface. Otherwise, both global and local definitions are
2580
	used. Could also be used to disable RDNSS for given interface
2581
	if no local definitons are specified. Default: no.
2582

    
2583
	<tag>dnssl local <m/switch/</tag>
2584
	Use only local DNSSL definitions for this interface. See
2585
	<cf/rdnss local/ option above. Default: no.
2586
</descrip>
2587

    
2588

    
2589
<p>Prefix specific options:
2590

    
2591
<descrip>
2592
	<tag>skip <m/switch/</tag>
2593
	This option allows to specify that given prefix should not be
2594
	advertised. This is useful for making exceptions from a
2595
	default policy of advertising all prefixes. Note that for
2596
	withdrawing an already advertised prefix it is more useful to
2597
	advertise it with zero valid lifetime. Default: no
2598

    
2599
	<tag>onlink <m/switch/</tag>
2600
	This option specifies whether hosts may use the advertised
2601
	prefix for onlink determination. Default: yes
2602

    
2603
	<tag>autonomous <m/switch/</tag>
2604
	This option specifies whether hosts may use the advertised
2605
	prefix for stateless autoconfiguration. Default: yes
2606

    
2607
	<tag>valid lifetime <m/expr/ [sensitive <m/switch/]</tag>
2608
	This option specifies the time (in seconds) how long (after
2609
	the receipt of RA) the prefix information is valid, i.e.,
2610
	autoconfigured IP addresses can be assigned and hosts with
2611
	that IP addresses are considered directly reachable. 0 means
2612
	the prefix is no longer valid. For <cf/sensitive/ option, see
2613
	<ref id="dsc-trigger" name="trigger">. Default: 86400 (1 day), <cf/sensitive/ no.
2614

    
2615
	<tag>preferred lifetime <m/expr/ [sensitive <m/switch/]</tag>
2616
	This option specifies the time (in seconds) how long (after
2617
	the receipt of RA) IP addresses generated from the prefix
2618
	using stateless autoconfiguration remain preferred. For
2619
	<cf/sensitive/ option, see <ref id="dsc-trigger" name="trigger">.
2620
	Default: 14400 (4 hours), <cf/sensitive/ no.
2621
</descrip>
2622

    
2623

    
2624
<p>RDNSS specific options:
2625

    
2626
<descrip>
2627
	<tag>ns <m/address/</tag>
2628
	This option specifies one recursive DNS server. Can be used
2629
	multiple times for multiple servers. It is mandatory to have
2630
	at least one <cf/ns/ option in <cf/rdnss/ definition.
2631

    
2632
	<tag>lifetime [mult] <m/expr/</tag>
2633
	This option specifies the time how long the RDNSS information
2634
        may be used by clients after the receipt of RA. It is
2635
        expressed either in seconds or (when <cf/mult/ is used) in
2636
        multiples of <cf/max ra interval/. Note that RDNSS information
2637
        is also invalidated when <cf/default lifetime/ expires. 0
2638
        means these addresses are no longer valid DNS servers.
2639
	Default: 3 * <cf/max ra interval/.
2640
</descrip>
2641

    
2642

    
2643
<p>DNSSL specific options:
2644

    
2645
<descrip>
2646
	<tag>domain <m/address/</tag>
2647
	This option specifies one DNS search domain. Can be used
2648
	multiple times for multiple domains. It is mandatory to have
2649
	at least one <cf/domain/ option in <cf/dnssl/ definition.
2650

    
2651
	<tag>lifetime [mult] <m/expr/</tag>
2652
	This option specifies the time how long the DNSSL information
2653
        may be used by clients after the receipt of RA. Details are
2654
	the same as for RDNSS <cf/lifetime/ option above.
2655
	Default: 3 * <cf/max ra interval/.
2656
</descrip>
2657

    
2658

    
2659
<sect1>Example
2660

    
2661
<p><code>
2662
protocol radv {
2663
	interface "eth2" {
2664
		max ra interval 5;	# Fast failover with more routers
2665
		managed yes;		# Using DHCPv6 on eth2
2666
		prefix ::/0 {
2667
			autonomous off;	# So do not autoconfigure any IP
2668
		};
2669
	};
2670

    
2671
	interface "eth*";		# No need for any other options
2672

    
2673
	prefix 2001:0DB8:1234::/48 {
2674
		preferred lifetime 0;	# Deprecated address range
2675
	};
2676

    
2677
	prefix 2001:0DB8:2000::/48 {
2678
		autonomous off;		# Do not autoconfigure
2679
	};
2680

    
2681
	rdnss 2001:0DB8:1234::10;	# Short form of RDNSS
2682

    
2683
	rdnss {
2684
		lifetime mult 10;
2685
		ns 2001:0DB8:1234::11;
2686
		ns 2001:0DB8:1234::12;
2687
	};
2688

    
2689
	dnssl {
2690
		lifetime 3600;
2691
		domain "abc.com";
2692
		domain "xyz.com";
2693
	};
2694
}
2695
</code>
2696

    
2697
<sect>RIP
2698

    
2699
<sect1>Introduction
2700

    
2701
<p>The RIP protocol (also sometimes called Rest In Pieces) is a simple protocol, where each router broadcasts (to all its neighbors)
2702
distances to all networks it can reach. When a router hears distance to another network, it increments
2703
it and broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some network goes
2704
unreachable, routers keep telling each other that its distance is the original distance plus 1 (actually, plus
2705
interface metric, which is usually one). After some time, the distance reaches infinity (that's 15 in
2706
RIP) and all routers know that network is unreachable. RIP tries to minimize situations where
2707
counting to infinity is necessary, because it is slow. Due to infinity being 16, you can't use
2708
RIP on networks where maximal distance is higher than 15 hosts. You can read more about RIP at <HTMLURL
2709
URL="http://www.ietf.org/html.charters/rip-charter.html" name="http://www.ietf.org/html.charters/rip-charter.html">. Both IPv4  
2710
(RFC 1723<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc1723.txt">)
2711
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
2712
not currently supported. RIPv4 MD5 authentication (RFC 2082<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc2082.txt">) is supported.
2713

    
2714
<p>RIP is a very simple protocol, and it has a lot of shortcomings. Slow
2715
convergence, big network load and inability to handle larger networks
2716
makes it pretty much obsolete. (It is still usable on very small networks.)
2717

    
2718
<sect1>Configuration
2719

    
2720
<p>In addition to options common for all to other protocols, RIP supports the following ones:
2721

    
2722
<descrip>
2723
	<tag/authentication none|plaintext|md5/ selects authentication method to be used. <cf/none/ means that
2724
	  packets are not authenticated at all, <cf/plaintext/ means that a plaintext password is embedded
2725
	  into each packet, and <cf/md5/ means that packets are authenticated using a MD5 cryptographic
2726
	  hash. If you set authentication to not-none, it is a good idea to add <cf>password</cf>
2727
	  section. Default: none.
2728

    
2729
	<tag>honor always|neighbor|never </tag>specifies when should requests for dumping routing table
2730
	  be honored. (Always, when sent from a  host on a directly connected
2731
	  network or never.) Routing table updates are honored only from
2732
	  neighbors, that is not configurable. Default: never.
2733
</descrip>
2734

    
2735
<p>There are two options that can be specified per-interface. First is <cf>metric</cf>, with
2736
default one.  Second is <cf>mode multicast|broadcast|quiet|nolisten|version1</cf>, it selects mode for
2737
rip to work in. If nothing is specified, rip runs in multicast mode. <cf>version1</cf> is
2738
currently equivalent to <cf>broadcast</cf>, and it makes RIP talk to a broadcast address even
2739
through multicast mode is possible. <cf>quiet</cf> option means that RIP will not transmit
2740
any periodic messages to this interface and <cf>nolisten</cf> means that RIP will send to this
2741
interface but not listen to it.
2742

    
2743
<p>The following options generally override behavior specified in RFC. If you use any of these
2744
options, BIRD will no longer be RFC-compliant, which means it will not be able to talk to anything
2745
other than equally configured BIRD. I have warned you.
2746

    
2747
<descrip>
2748
	<tag>port <M>number</M></tag>
2749
	  selects IP port to operate on, default 520. (This is useful when testing BIRD, if you
2750
	  set this to an address &gt;1024, you will not need to run bird with UID==0).
2751

    
2752
	<tag>infinity <M>number</M></tag>
2753
	  selects the value of infinity, default is 16. Bigger values will make protocol convergence
2754
	  even slower.
2755

    
2756
	<tag>period <M>number</M>
2757
	  </tag>specifies the number of seconds between periodic updates. Default is 30 seconds. A lower
2758
	  number will mean faster convergence but bigger network
2759
	  load. Do not use values lower than 12.
2760

    
2761
	<tag>timeout time <M>number</M>
2762
	  </tag>specifies how old route has to be to be considered unreachable. Default is 4*<cf/period/.
2763

    
2764
	<tag>garbage time <M>number</M>
2765
	  </tag>specifies how old route has to be to be discarded. Default is 10*<cf/period/.
2766
</descrip>
2767

    
2768
<sect1>Attributes
2769

    
2770
<p>RIP defines two route attributes:
2771

    
2772
<descrip>
2773
	<tag>int <cf/rip_metric/</tag> RIP metric of the route (ranging from 0 to <cf/infinity/).
2774
	When routes from different RIP instances are available and all of them have the same
2775
	preference, BIRD prefers the route with lowest <cf/rip_metric/.
2776
	When importing a non-RIP route, the metric defaults to 5.
2777

    
2778
	<tag>int <cf/rip_tag/</tag> RIP route tag: a 16-bit number which can be used
2779
	to carry additional information with the route (for example, an originating AS number
2780
	in case of external routes). When importing a non-RIP route, the tag defaults to 0.
2781
</descrip>
2782

    
2783
<sect1>Example
2784

    
2785
<p><code>
2786
protocol rip MyRIP_test {
2787
        debug all;
2788
        port 1520;
2789
        period 12;
2790
        garbage time 60;
2791
        interface "eth0" { metric 3; mode multicast; };
2792
	interface "eth*" { metric 2; mode broadcast; };
2793
        honor neighbor;
2794
        authentication none;
2795
        import filter { print "importing"; accept; };
2796
        export filter { print "exporting"; accept; };
2797
}
2798
</code>
2799

    
2800
<sect>Static
2801

    
2802
<p>The Static protocol doesn't communicate with other routers in the network,
2803
but instead it allows you to define routes manually. This is often used for
2804
specifying how to forward packets to parts of the network which don't use
2805
dynamic routing at all and also for defining sink routes (i.e., those
2806
telling to return packets as undeliverable if they are in your IP block,
2807
you don't have any specific destination for them and you don't want to send
2808
them out through the default route to prevent routing loops).
2809

    
2810
<p>There are five types of static routes: `classical' routes telling
2811
to forward packets to a neighboring router, multipath routes
2812
specifying several (possibly weighted) neighboring routers, device
2813
routes specifying forwarding to hosts on a directly connected network,
2814
recursive routes computing their nexthops by doing route table lookups
2815
for a given IP and special routes (sink, blackhole etc.) which specify
2816
a special action to be done instead of forwarding the packet.
2817

    
2818
<p>When the particular destination is not available (the interface is down or
2819
the next hop of the route is not a neighbor at the moment), Static just
2820
uninstalls the route from the table it is connected to and adds it again as soon
2821
as the destination becomes adjacent again.
2822

    
2823
<p>The Static protocol does not have many configuration options. The
2824
definition of the protocol contains mainly a list of static routes:
2825

    
2826
<descrip>
2827
	<tag>route <m/prefix/ via <m/ip/</tag> Static route through
2828
	a neighboring router.
2829
	<tag>route <m/prefix/ multipath via <m/ip/ [weight <m/num/] [via ...]</tag>
2830
	Static multipath route. Contains several nexthops (gateways), possibly
2831
 	with their weights.
2832
	<tag>route <m/prefix/ via <m/"interface"/</tag> Static device
2833
	route through an interface to hosts on a directly connected network.
2834
	<tag>route <m/prefix/ recursive <m/ip/</tag> Static recursive route,
2835
	its nexthop depends on a route table lookup for given IP address.
2836
	<tag>route <m/prefix/ blackhole|unreachable|prohibit</tag> Special routes
2837
	specifying to silently drop the packet, return it as unreachable or return
2838
	it as administratively prohibited. First two targets are also known
2839
	as <cf/drop/ and <cf/reject/.
2840

    
2841
	<tag>check link <m/switch/</tag>
2842
	If set, hardware link states of network interfaces are taken
2843
	into consideration.  When link disappears (e.g. ethernet cable
2844
	is unplugged), static routes directing to that interface are
2845
	removed. It is possible that some hardware drivers or
2846
	platforms do not implement this feature. Default: off.
2847

    
2848
	<tag>igp table <m/name/</tag> Specifies a table that is used
2849
	for route table lookups of recursive routes. Default: the
2850
	same table as the protocol is connected to.
2851
</descrip>
2852

    
2853
<p>Static routes have no specific attributes.
2854

    
2855
<p>Example static config might look like this:
2856

    
2857
<p><code>
2858
protocol static {
2859
	table testable;			 # Connect to a non-default routing table
2860
	route 0.0.0.0/0 via 198.51.100.130; # Default route
2861
	route 10.0.0.0/8 multipath	 # Multipath route
2862
		via 198.51.100.10 weight 2
2863
		via 198.51.100.20
2864
		via 192.0.2.1;
2865
	route 203.0.113.0/24 unreachable; # Sink route
2866
	route 10.2.0.0/24 via "arc0";	 # Secondary network
2867
}
2868
</code>
2869

    
2870
<chapt>Conclusions
2871

    
2872
<sect>Future work
2873

    
2874
<p>Although BIRD supports all the commonly used routing protocols,
2875
there are still some features which would surely deserve to be
2876
implemented in future versions of BIRD:
2877

    
2878
<itemize>
2879
<item>Opaque LSA's
2880
<item>Route aggregation and flap dampening
2881
<item>Multipath routes
2882
<item>Multicast routing protocols
2883
<item>Ports to other systems
2884
</itemize>
2885

    
2886
<sect>Getting more help
2887

    
2888
<p>If you use BIRD, you're welcome to join the bird-users mailing list
2889
(<HTMLURL URL="mailto:bird-users@bird.network.cz" name="bird-users@bird.network.cz">)
2890
where you can share your experiences with the other users and consult
2891
your problems with the authors. To subscribe to the list, just send a
2892
<tt/subscribe bird-users/ command in a body of a mail to
2893
(<HTMLURL URL="mailto:majordomo@bird.network.cz" name="majordomo@bird.network.cz">).
2894
The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
2895

    
2896
<p>BIRD is a relatively young system and it probably contains some
2897
bugs. You can report any problems to the bird-users list and the authors
2898
will be glad to solve them, but before you do so,
2899
please make sure you have read the available documentation and that you are running the latest version (available at <HTMLURL
2900
URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">). (Of course, a patch
2901
which fixes the bug is always welcome as an attachment.)
2902

    
2903
<p>If you want to understand what is going inside, Internet standards are
2904
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">).
2905

    
2906
<p><it/Good luck!/
2907

    
2908
</book>
2909

    
2910
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2911
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