38-46
Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter38 Configuring IP Unicast Routing
Configuring BGP
BGP Version 4 supports classless interdomain routing (CIDR) so you can reduce the size of your routing
tables by creating aggregate routes, resulting in supernets. CIDR eliminates the concept of network
classes within BGP and supports the advertising of IP prefixes.
These sections contain this configuration information:
Default BGP Configuration, page38-46
Enabling BGP Routing, page38-49
Managing Routing Policy Changes, page38-51
Configuring BGP Decision Attributes, page38-53
Configuring BGP Filtering with Route Maps, page38-55
Configuring BGP Filtering by Neighbor, page38-55
Configuring Prefix Lists for BGP Filtering, page38-57
Configuring BGP Community Filtering, page38-58
Configuring BGP Neighbors and Peer Groups, page38-59
Configuring Aggregate Addresses, page38-61
Configuring Routing Domain Confederations, page38-62
Configuring BGP Route Reflectors, page38-62
Configuring Route Dampening, page38-63
Monitoring and Maintaining BGP, page38-64
For detailed descriptions of BGP configuration, see the “Configuring BGP” chapter in the “IP Routing
Protocols” part of the Cisco IOS IP Configuration Guide, Release 12.2. For details about specific
commands, see the Cisco IOS IP Command Reference, Volume 2 of 3: Routing Protocols, Release 12.2.
Locate these documents from the Cisco.com page under Documentation > Cisco IOS Software > 12.2
Mainline > Configuration Guides or Command References.
For a list of BGP commands that are visible but not supported by the switch, see AppendixD,
“Unsupported Commands in Cisco IOS Release 12.2(55)SE.”
Default BGP Configuration
Table38-9 shows the basic default BGP configuration. For the defaults for all characteristics, see the
specific commands in the Cisco IOS IP Command Reference, Volume 2 of 3: Routing Protocols,
Release 12.2.
Table38-9 Default BGP Configuration
Feature Default Setting
Aggregate address Disabled: None defined.
AS path access list None defined.
Auto summary Enabled.
Best path The router considers as-path in choosing a route and does not compare similar
routes from external BGP peers.
Compare router ID: Disabled.