Concept Guide

• After a route matches a lter, the lter’s action is applied. No additional lters are applied to the route.
To view the BGP conguration, use the show config command in ROUTER BGP mode. To view a prex list conguration, use the show
ip prefix-list detail
or show ip prefix-list summary commands in EXEC Privilege mode.
Filtering BGP Routes Using Route Maps
To lter routes using a route map, use these commands.
1 Create a route map and assign it a name.
CONFIGURATION mode
route-map map-name [permit | deny] [sequence-number]
2 Create multiple route map lters with a match or set action.
CONFIG-ROUTE-MAP mode
{match | set}
For information about conguring route maps, refer to Access Control Lists (ACLs).
3 Return to CONFIGURATION mode.
CONFIG-ROUTE-MAP mode
exit
4 Enter ROUTER BGP mode.
CONFIGURATION mode
router bgp as-number
5 Filter routes based on the criteria in the congured route map.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | peer-group-name} route-map map-name {in | out}
Congure the following parameters:
• ip-address or peer-group-name: enter the neighbor’s IP address or the peer group’s name.
• map-name: enter the name of a congured route map.
• in: apply the route map to inbound routes.
• out: apply the route map to outbound routes.
To view the BGP conguration, use the show config command in CONFIGURATION ROUTER BGP mode. To view a route map
conguration, use the show route-map command in EXEC Privilege mode.
Filtering BGP Routes Using AS-PATH Information
To lter routes based on AS-PATH information, use these commands.
1 Create a AS-PATH ACL and assign it a name.
CONFIGURATION mode
ip as-path access-list as-path-name
2 Create a AS-PATH ACL lter with a deny or permit action.
AS-PATH ACL mode
{deny | permit} as-regular-expression
3 Return to CONFIGURATION mode.
AS-PATH ACL
Border Gateway Protocol IPv4 (BGPv4)
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