Setup Guide
ip prefix-list prefix-name
2 Create multiple prex list lters with a deny or permit action.
CONFIG-PREFIX LIST mode
seq sequence-number {deny | permit} {any | ip-prefix [ge | le] }
• ge: minimum prex length to be matched.
• le: maximum prex length to me matched.
For information about conguring prex 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 congured prex list.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | ipv6-address | peer-group-name} distribute-list prefix-list-name {in |
out}
Congure 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 congured prex list.
• in: apply the prex list to inbound routes.
• out: apply the prex list to outbound routes.
As a reminder, the following are rules concerning prex lists:
• If the prex list contains no lters, all routes are permitted.
• If none of the routes match any of the lters in the prex list, the route is denied. This action is called an implicit deny. (If you want to
forward all routes that do not match the prex list criteria, you must congure a prex list lter to permit all routes. For example, you
could have the following lter as the last lter in your prex 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 conguring an IP prex 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 conguration of an IP prex list named route10, which permits routes to network 10.10.10.0/24. The neighbor
command congures to use IP prex 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 prex list
route10 explicitly permits the routes to be distributed
to the neighbor.
To view the BGP conguration, use the show config command in ROUTER BGP mode. To view a prex list conguration, use the show
ip prefix-list detail or show ip prefix-list summary commands in EXEC Privilege mode.
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Border Gateway Protocol (BGP)