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Don't let example overflow, and new chapter for "about routing tables".
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@ -98,42 +98,6 @@ be relatively easy due to its highly modular architecture.
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<p>This documentation can have 4 forms: sgml (this is master copy), html, ASCII text and dvi/postscript (generated from sgml using sgmltools). You should always edit master copy.
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<p>This documentation can have 4 forms: sgml (this is master copy), html, ASCII text and dvi/postscript (generated from sgml using sgmltools). You should always edit master copy.
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<sect>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 kernel and which may or may not be synchronized with
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each other (see the Pipe protocol). Each routing table contains list of
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known routes. Each route consists of:
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<itemize>
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<item>network this route is for
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<item>preference of this route (taken from preference of
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protocol and possibly altered by filters)
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<item>ip address of router who told us about this route
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<item>ip address of router we should use for packets routing
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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 metric)
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</itemize>
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Routing table maintains more than
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one entry for network, but at most one entry for one network and one
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protocol. The entry with biggest preference is used for routing. If
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there are more entries with same preference and they are from same
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protocol, protocol decides (typically according to metrics). If not,
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internal ordering is used to decide. You can
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get list of route attributes in "Route attributes" section in
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filters.
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<p>Protocols are connected to routing tables using filters. Routes
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that come from network go to the protocol, it then passes them to
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filters, if import filter accepts route, it gets to main routing
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table. It is then broadcasted to all other protocols (filtered through
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their export filters), which typically send it to the network.
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Filters can alter routes passed between routing tables and
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protocols.
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<sect>Installing BIRD
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<sect>Installing BIRD
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@ -173,6 +137,43 @@ options. Most important (and not easily guessed) option is
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use given filename for socket for communications with bird client, default is <file/bird.ctl/.
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use given filename for socket for communications with bird client, default is <file/bird.ctl/.
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</descrip>
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</descrip>
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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 kernel and which may or may not be synchronized with
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each other (see the Pipe protocol). Each routing table contains list of
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known routes. Each route consists of:
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<itemize>
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<item>network this route is for
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<item>preference of this route (taken from preference of
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protocol and possibly altered by filters)
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<item>ip address of router who told us about this route
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<item>ip address of router we should use for packets routing
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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 metric)
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</itemize>
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Routing table maintains more than
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one entry for network, but at most one entry for one network and one
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protocol. The entry with biggest preference is used for routing. If
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there are more entries with same preference and they are from same
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protocol, protocol decides (typically according to metrics). If not,
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internal ordering is used to decide. You can
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get list of route attributes in "Route attributes" section in
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filters.
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<p>Protocols are connected to routing tables using filters. Routes
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that come from network go to the protocol, it then passes them to
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filters, if import filter accepts route, it gets to main routing
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table. It is then broadcasted to all other protocols (filtered through
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their export filters), which typically send it to the network.
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Filters can alter routes passed between routing tables and
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protocols.
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<chapt>Configuration
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<chapt>Configuration
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<sect>Introduction
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<sect>Introduction
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@ -741,9 +742,12 @@ protocol bgp {
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multihop 20 via 62.168.0.13; # Which is connected indirectly
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multihop 20 via 62.168.0.13; # Which is connected indirectly
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export filter { # We use non-trivial export rules
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export filter { # We use non-trivial export rules
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if source = RTS_STATIC then { # Export only static routes
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if source = RTS_STATIC then { # Export only static routes
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bgp_community.add((65000,5678)); # Assign our community
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# Assign our community
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if bgp_path ~ / 65000 / then # Artificially increase path length
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bgp_community.add((65000,5678));
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bgp_path.prepend(65000); # by prepending local AS number twice
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# Artificially increase path length
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# by prepending local AS number twice
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if bgp_path ~ / 65000 / then
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bgp_path.prepend(65000);
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accept;
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accept;
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}
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}
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reject;
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reject;
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