Concept Guide
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Filtering Routes with Community Lists
To use an IP community list or IP extended community list to lter routes, you must apply a match community lter to a route map and then
apply that route map to a BGP neighbor or peer group.
1 Enter the ROUTE-MAP mode and assign a name to a route map.
CONFIGURATION mode
route-map map-name [permit | deny] [sequence-number]
2 Congure a match lter for all routes meeting the criteria in the IP community or IP extended community list.
CONFIG-ROUTE-MAP mode
match {community community-list-name [exact] | extcommunity extcommunity-list-name [exact]}
3 Return to CONFIGURATION mode.
CONFIG-ROUTE-MAP mode
exit
4 Enter ROUTER BGP mode.
CONFIGURATION mode
router bgp as-number
AS-number: 0 to 65535 (2-Byte) or 1 to 4294967295 (4-Byte) or 0.1 to 65535.65535 (Dotted format)
5 Apply the route map to the neighbor or peer group’s incoming or outgoing routes.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | ipv6-address | peer-group-name} route-map map-name {in | out}
Example conguration for ltering routes with community lists
DellEMC# configure terminal
DellEMC(conf)# router bgp 400
DellEMC(conf-router_bgp)# neighbor 10.10.10.1 remote-as 500
DellEMC(conf-router_bgp)# neighbor 10.10.10.1 route-map route2 in
DellEMC(conf-router_bgp)# exit
DellEMC(conf)# route-map route2 permit 10
DellEMC(conf-route-map)# match community 1
DellEMC(conf-route-map)# set community 99
DellEMC(conf-route-map)# exit
DellEMC(conf)# ip community-list 1 permit 100
DellEMC(conf)# exit
DellEMC#
In the above example, add a BGP neighbor to the AS 400 and the route-map called route2 applied to inbound routes from the BGP
neighbor at 10.10.10.1. A route map route2 is created with a permit clause and the route’s community attribute is matched to communities
in community list 1. A community list 1 that permits routes with a communities attribute of 100.
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Border Gateway Protocol (BGP)