Commit a852c139 authored by Pavel Machek's avatar Pavel Machek

Don't let example overflow, and new chapter for "about routing tables".

parent ee4880c8
......@@ -98,42 +98,6 @@ be relatively easy due to its highly modular architecture.
<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.
<sect>About routing tables
<p>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:
<itemize>
<item>network this route is for
<item>preference of this route (taken from preference of
protocol and possibly altered by filters)
<item>ip address of router who told us about this route
<item>ip address of router we should use for packets routing
using this route
<item>other attributes common to all routes
<item>dynamic attributes defined by protocols, which may or
may not be present (typically protocol metric)
</itemize>
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.
<p>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.
<sect>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 <file/bird.ctl/.
</descrip>
<chapt>About routing tables
<p>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:
<itemize>
<item>network this route is for
<item>preference of this route (taken from preference of
protocol and possibly altered by filters)
<item>ip address of router who told us about this route
<item>ip address of router we should use for packets routing
using this route
<item>other attributes common to all routes
<item>dynamic attributes defined by protocols, which may or
may not be present (typically protocol metric)
</itemize>
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.
<p>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.
<chapt>Configuration
<sect>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;
......
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