Cisco Systems 78-11741-02 manual BGP Prefix List Filtering Examples, IPC-337

Configuring BGP

BGP Configuration Examples

Figure 58 Assigning Internal and External BGP Neighbors

RouterRouter

Router

Router A Internal BGP

AS 109

131.108.0.0

192.31.7.0

RouterRouter

131.108.200.1	150.136.64.19
AS 167	AS 99

Router

131.108.234.2

S1270a

BGP Prefix List Filtering Examples

The following examples show route filtering using a single prefix list and a group of prefixes, and how to add or delete an individual entry from a prefix list.

Route Filtering Configuration Example Using a Single Prefix List

The following example shows how a prefix list denies the default route 0.0.0.0/0:

ip prefix-list abc deny 0.0.0.0/0

The following example shows how a prefix list permits a route that matches the prefix 35.0.0.0/8:

ip prefix-list abc permit 35.0.0.0/8

The following example shows how to configure the BGP process so that it only accept prefixes with a prefix length of /8 to /24:

router bgp version 2 network 101.20.20.0

distribute-list prefix max24 in

!

ip prefix-list max24 seq 5 permit 0.0.0.0/0 ge 8 le 24

Cisco IOS IP Configuration Guide

IPC-337