Filter
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configure a prefix list filter to permit all routes. For example, you could have the following filter as the
last filter in your prefix list permit 0.0.0.0/0 le 32).
• After a route matches a filter, the filter’s action is applied. No additional filters are applied to the route.
To view the BGP configuration, use the show config command in ROUTER BGP mode. To view a prefix
list configuration, 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 filter 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 filters with a match or set action.
CONFIG-ROUTE-MAP mode
{match | set}
For information about configuring 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 configured route map.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | peer-group-name} route-map map-name {in | out}
Configure 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 configured route map.
• in: apply the route map to inbound routes.
• out: apply the route map to outbound routes.
To view the BGP configuration, use the show config command in CONFIGURATION ROUTER BGP
mode. To view a route map configuration, use the show route-map command in EXEC Privilege mode.
Filtering BGP Routes Using AS-PATH Information
To filter 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)