From a2a3ced83eea3919639adafbdacb7ec11011f9cb Mon Sep 17 00:00:00 2001 From: Martin Mares Date: Wed, 31 May 2000 10:07:27 +0000 Subject: [PATCH] Added Pipe documentation. --- doc/bird.sgml | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 100 insertions(+) diff --git a/doc/bird.sgml b/doc/bird.sgml index 8a274e0d..e5e29074 100644 --- a/doc/bird.sgml +++ b/doc/bird.sgml @@ -753,6 +753,7 @@ protocol kernel { # Secondary routing table table auxtable; kernel table 100; export all; +}

The Kernel protocol doesn't define any route attributes. @@ -761,6 +762,105 @@ protocol kernel { # Secondary routing table Pipe +Introduction + +

The Pipe protocol serves as a link between two routing tables, allowing routes to be +passed from a table declared as primary (i.e., the one the pipe is connected using the +The primary use of multiple routing tables and the pipe protocol is for policy routing +where handling of a single packet doesn't depend only on its destination address, but also +on its source address, source interface, protocol type and other similar parameters. +In many OS'es (Linux 2.2 being a good example) the kernel allows to enforce routing policies +by defining routing rules which choose one of several routing tables to be used for a packet +according to its parameters. Setting of these rules is outside the scope of BIRD's work +(you can use the Configuration + +

+ peer table Define secondary routing table to connect to. The + primary one is selected by the + +Attributes + +

The Pipe protocol doesn't define any route attributes. + +Example + +

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

Probably the simplest solution to this situation is to use two routing tables (we'll +call them +table as1; # Define the tables +table as2; + +protocol kernel kern1 { # Synchronize them with the kernel + table as1; + kernel table 1; +} + +protocol kernel kern2 { + table as2; + kernel table 2; +} + +protocol bgp bgp1 { # The outside connections + table as1; + local as 1; + neighbor 192.168.0.1 as 1001; + export all; + import all; +} + +protocol bgp bgp2 { + table as2; + local as 2; + neighbor 10.0.0.1 as 1002; + export all; + import all; +} + +protocol pipe { # The Pipe + table as1; + peer table as2; + export filter { + if net ~ [ 1.0.0.0/8+] then { # Only AS1 networks + if preference>10 then preference = preference-10; + if source=RTS_BGP then bgp_path.prepend(1); + accept; + } + reject; + }; + import filter { + if net ~ [ 2.0.0.0/8+] then { # Only AS2 networks + if preference>10 then preference = preference-10; + if source=RTS_BGP then bgp_path.prepend(2); + accept; + } + reject; + }; +} + + Rip Introduction