Concept Guide

ip prefix-list prefix-name
2 Create multiple prex list lters with a deny or permit action.
CONFIG-PREFIX LIST mode
seq sequence-number {deny | permit} {any | ip-prefix [ge | le] }
• ge: minimum prex length to be matched.
• le: maximum prex length to me matched.
For information about conguring prex 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 congured prex list.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | ipv6-address | peer-group-name} distribute-list prefix-list-name {in |
out}
Congure the following parameters:
• ip-address or ipv6-address or peer-group-name: enter the neighbor’s IPv4 or IPv6 address or the peer group’s name.
• prefix-list-name: enter the name of a congured prex list.
• in: apply the prex list to inbound routes.
• out: apply the prex list to outbound routes.
As a reminder, the following are rules concerning prex lists:
• If the prex list contains no lters, all routes are permitted.
• If none of the routes match any of the lters in the prex list, the route is denied. This action is called an implicit deny. (If you want to
forward all routes that do not match the prex list criteria, you must congure a prex list lter to permit all routes. For example, you
could have the following lter as the last lter in your prex 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.
Example of conguring an IP prex list and applying it to a BGP neighbor
DellEMC# configure terminal
DellEMC(conf)# ip prefix-list route10
DellEMC(conf)# seq 10 permit 10.10.10.0/24 ge 32
DellEMC(conf)#exit
DellEMC(conf)# router bgp
DellEMC(conf-router_bgp)#neighbor 10.10.10.2 distribute-list route10 out
The commands show the conguration of an IP prex list named route10, which permits routes to network 10.10.10.0/24. The neighbor
command congures to use IP prex list route10 to determine, which routes to be distributed to the neighbor 10.10.10.2. So the routes
from 10.10.10.1/24 network is distributed to neighbor 10.10.10.2 since the IP prex list
route10 explicitly permits the routes to be distributed
to the neighbor.
To view the BGP conguration, use the show config command in ROUTER BGP mode. To view a prex list conguration, use the show
ip prefix-list detail or show ip prefix-list summary commands in EXEC Privilege mode.
Border Gateway Protocol (BGP)
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