Dell Force10 S25N-S50N FTOS Configuration Guide FTOS 8.4.2.7 E-Series TeraScal - Page 255

Refer to Chapter 8, "IP Access Control Lists (ACL), Prefix Lists, and Route-maps," on page 133 for configuration information on prefix lists, AS-PATH ACLs, and route maps. Note: When you configure a new set of BGP policies, always reset the neighbor or peer group by entering the clear ip bgp command in EXEC Privilege mode. Use these commands in the following sequence, starting in the CONFIGURATION mode to filter routes using prefix lists. Step Command Syntax 1 ip prefix-list prefix-name 2 seq sequence-number {deny | permit} {any | ip-prefix [ge | le] } 3 exit 4 router bgp as-number 5 neighbor {ip-address | peer-group-name} distribute-list prefix-list-name {in | out} Command Mode CONFIGURATION CONFIG-PREFIX LIST CONFIG-PREFIX LIST CONFIGURATION CONFIG-ROUTERBGP Purpose Create a prefix list and assign it a name. Create multiple prefix list filters with a deny or permit action. ge: Minimum prefix length to be matched le: maximum prefix length to me matched Refer to Chapter 8, "IP Access Control Lists (ACL), Prefix Lists, and Route-maps," on page 133 for information on configuring prefix lists. Return to the CONFIGURATION mode. Enter ROUTER BGP mode. Filter routes based on the criteria in the configured prefix list. Configure the following parameters: • ip-address or peer-group-name: enter the neighbor's IP address or the peer group's name. • prefix-list-name: enter the name of a configured prefix list. • in: apply the prefix list to inbound routes. • out: apply the prefix list to outbound routes. As a reminder, below are some rules concerning prefix lists: • 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 called an implicit deny. (If you want to forward all routes that do not match the prefix list criteria, you must 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). • Once 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 the 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. Border Gateway Protocol IPv4 (BGPv4) | 255