Reference Guide

Border Gateway Protocol IPv4 (BGPv4) | 213
Regular Expressions as filters:
Regular expressions are used to filter AS paths or community lists. A regular expression is a special
character used to define a pattern that is then compared with an input string.
For an AS-path access list as shown in the commands above, if the AS path matches the regular expression
in the access list, then the route matches the access list.
The example below applies access list Eagle to routes inbound from BGP peer 10.5.5.2. Access list Eagle
uses a regular expression to deny routes originating in AS 32.
4
router bgp as-number CONFIGURATION Enter ROUTER BGP mode.
5 neighbor {ip-address |
peer-group-name}
filter-list as-path-name {in
|
out}
CONFIG-ROUTER-B
GP
Use a configured AS-PATH ACL for route filtering and
manipulation.
If you assign an non-existent or empty AS-PATH ACL,
the software allows all routes.
Step Command Syntax Command Mode Purpose