9.2
Route Filtering and Manipulation Process (Policies)
9.2.5 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 !
 

The example in the Figure shows how to configure Router A with a prefix list so that it can send only 172.0.0.0/8 update to AS 65000, not 172.30.0.0/16.

Lab Activity
  In this lab, you will learn how to use a prefix list to filter routes.