• If the prefix list contains no filters, all routes are permitted.• If none of the routes match any of the filters in the prefix list, the route is denied. This action is calledan implicit deny. (If you want to forward all routes that do not match the prefix list criteria, you mustconfigure a prefix list filter to permit all routes. For example, you could have the following filter as thelast 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 prefixlist configuration, use the show ip prefix-list detail or show ip prefix-list summarycommands in EXEC Privilege mode.Filtering BGP Routes Using Route MapsTo filter routes using a route map, use these commands.1. Create a route map and assign it a name.CONFIGURATION moderoute-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 modeexit4. Enter ROUTER BGP mode.CONFIGURATION moderouter bgp as-number5. Filter routes based on the criteria in the configured route map.CONFIG-ROUTER-BGP modeneighbor {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 BGPmode. To view a route map configuration, use the show route-map command in EXEC Privilege mode.Border Gateway Protocol IPv4 (BGPv4) 211
