Using BGP Communities

Problem

You want to configure BGP Communities to control routing and route propagation.

Solution

Configuring Cisco routers to use BGP Communities is a two-step process. You must specify the desired Community values by using a route map associated with a neighbor command:

Router3#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router3(config)#ip prefix-list 10.101/16 seq 5 permit 10.101.0.0/16
Router3(config)#ip prefix-list 10.102/16 seq 5 permit 10.102.0.0/16
Router3(config)#ip prefix-list 10.103/16 seq 5 permit 10.103.0.0/16
Router3(config)#ip prefix-list 10.104/16 seq 5 permit 10.104.0.0/16
Router3(config)#ip prefix-list 10.105/16 seq 5 permit 10.105.0.0/16
Router3(config)#route-map APPLY_COMMUNITY_A permit 10
Router3(config-route-map)#match ip address prefix-list 10.101/16
Router3(config-route-map)#set community no-advertise
Router3(config-route-map)#exit
Router3(config)#route-map APPLY_COMMUNITY_A permit 20
Router3(config-route-map)#match ip address prefix-list 10.102/16
Router3(config-route-map)#set community no-export
Router3(config-route-map)#exit
Router3(config)#route-map APPLY_COMMUNITY_A permit 30
Router3(config-route-map)#match ip address prefix-list 10.103/16
Router3(config-route-map)#set community local-AS
Router3(config-route-map)#exit
Router3(config)#route-map APPLY_COMMUNITY_A permit 40
Router3(config-route-map)#match ip address prefix-list 10.104/16
Router3(config-route-map)#set community internet Router3(config-route-map)# ...

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