Administrator Guide
• If none of the routes match any of the lters in the prex list, the route is denied. This action is called an implicit deny. (If you want to
forward all routes that do not match the prex list criteria, you must congure a prex list lter to permit all routes. For example, you
could have the following lter as the last lter in your prex list permit 0.0.0.0/0 le 32).
• After a route matches a lter, the lter’s action is applied. No additional lters are applied to the route.
To view the BGP conguration, use the show config command in ROUTER BGP mode. To view a prex list conguration, 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 conguring route maps, see 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 congured route map.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | peer-group-name} route-map map-name {in | out}
Congure 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 congured route map.
• in: apply the route map to inbound routes.
• out: apply the route map to outbound routes.
To view the BGP conguration, use the show config command in CONFIGURATION ROUTER BGP mode. To view a route map
conguration, 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
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Border Gateway Protocol IPv4 (BGPv4)