From a852c139dc90febae40be055050ed30490d823b8 Mon Sep 17 00:00:00 2001 From: Pavel Machek Date: Tue, 6 Jun 2000 11:05:12 +0000 Subject: [PATCH] Don't let example overflow, and new chapter for "about routing tables". --- doc/bird.sgml | 82 +++++++++++++++++++++++++++------------------------ 1 file changed, 43 insertions(+), 39 deletions(-) diff --git a/doc/bird.sgml b/doc/bird.sgml index 0945b24d..7ddf82c7 100644 --- a/doc/bird.sgml +++ b/doc/bird.sgml @@ -98,42 +98,6 @@ be relatively easy due to its highly modular architecture.

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. -About routing tables - -

Bird has one or more routing tables, which may or may not be -synchronized with kernel and which may or may not be synchronized with -each other (see the Pipe protocol). Each routing table contains list of -known routes. Each route consists of: - - - network this route is for - preference of this route (taken from preference of - protocol and possibly altered by filters) - ip address of router who told us about this route - ip address of router we should use for packets routing - using this route - other attributes common to all routes - dynamic attributes defined by protocols, which may or - may not be present (typically protocol metric) - - -Routing table maintains more than -one entry for network, but at most one entry for one network and one -protocol. The entry with biggest preference is used for routing. If -there are more entries with same preference and they are from same -protocol, protocol decides (typically according to metrics). If not, -internal ordering is used to decide. You can -get list of route attributes in "Route attributes" section in -filters. - -

Protocols are connected to routing tables using filters. Routes -that come from network go to the protocol, it then passes them to -filters, if import filter accepts route, it gets to main routing -table. It is then broadcasted to all other protocols (filtered through -their export filters), which typically send it to the network. - -Filters can alter routes passed between routing tables and -protocols. Installing BIRD @@ -173,6 +137,43 @@ options. Most important (and not easily guessed) option is use given filename for socket for communications with bird client, default is +About routing tables + +

Bird has one or more routing tables, which may or may not be +synchronized with kernel and which may or may not be synchronized with +each other (see the Pipe protocol). Each routing table contains list of +known routes. Each route consists of: + + + network this route is for + preference of this route (taken from preference of + protocol and possibly altered by filters) + ip address of router who told us about this route + ip address of router we should use for packets routing + using this route + other attributes common to all routes + dynamic attributes defined by protocols, which may or + may not be present (typically protocol metric) + + +Routing table maintains more than +one entry for network, but at most one entry for one network and one +protocol. The entry with biggest preference is used for routing. If +there are more entries with same preference and they are from same +protocol, protocol decides (typically according to metrics). If not, +internal ordering is used to decide. You can +get list of route attributes in "Route attributes" section in +filters. + +

Protocols are connected to routing tables using filters. Routes +that come from network go to the protocol, it then passes them to +filters, if import filter accepts route, it gets to main routing +table. It is then broadcasted to all other protocols (filtered through +their export filters), which typically send it to the network. + +Filters can alter routes passed between routing tables and +protocols. + Configuration Introduction @@ -741,9 +742,12 @@ protocol bgp { multihop 20 via 62.168.0.13; # Which is connected indirectly export filter { # We use non-trivial export rules if source = RTS_STATIC then { # Export only static routes - bgp_community.add((65000,5678)); # Assign our community - if bgp_path ~ / 65000 / then # Artificially increase path length - bgp_path.prepend(65000); # by prepending local AS number twice + # Assign our community + bgp_community.add((65000,5678)); + # Artificially increase path length + # by prepending local AS number twice + if bgp_path ~ / 65000 / then + bgp_path.prepend(65000); accept; } reject;