Dell PowerSwitch S4820T 9.50.1 Configuration Guide for the S4820T System - Page 225

For inbound and outbound updates the order of preference is: • prefix lists (using the neighbor distribute-list command) • AS-PATH ACLs (using the neighbor filter-list command) • route maps (using the neighbor route-map command) Prior to filtering BGP routes, create the prefix list, AS-PATH ACL, or route map. For configuration information about prefix lists, AS-PATH ACLs, and route maps, refer to Access Control Lists (ACLs). NOTE: When you configure a new set of BGP policies, to ensure the changes are made, always reset the neighbor or peer group by using the clear ip bgp command in EXEC Privilege mode. To filter routes using prefix lists, use the following commands. 1. Create a prefix list and assign it a name. CONFIGURATION mode ip prefix-list prefix-name 2. Create multiple prefix list filters with a deny or permit action. CONFIG-PREFIX LIST mode seq sequence-number {deny | permit} {any | ip-prefix [ge | le] } • ge: minimum prefix length to be matched. • le: maximum prefix length to me matched. For information about configuring prefix lists, refer to Access Control Lists (ACLs). 3. Return to CONFIGURATION mode. CONFIG-PREFIX LIST mode exit 4. Enter ROUTER BGP mode. CONFIGURATION mode router bgp as-number 5. Filter routes based on the criteria in the configured prefix list. CONFIG-ROUTER-BGP mode neighbor {ip-address | peer-group-name} distribute-list prefix-list-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. • 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, the following are rules concerning prefix lists: Border Gateway Protocol IPv4 (BGPv4) 225