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One way that BGP controls the distribution of routing information based on the value of the 
COMMUNITIES attribute. A community is a group of destinations that share some common attribute. 
Each destination can belong to multiple communities. AS administrators can define to which 
communities a destination belongs. By default, all destinations belong to the general Internet 
community. The community is identified by the COMMUNITIES attribute, an optional, transitive, 
global attribute in the numerical range from 1 to 4294967200. These are some predefined, well-known 
communities:

internet—Advertise this route to the Internet community. All routers belong to it.

no-export—Do not advertise this route to EBGP peers.

no-advertise—Do not advertise this route to any peer (internal or external).

local-as—Do not advertise this route to peers outside the local autonomous system. 

Based on the community, you can control which routing information to accept, prefer, or distribute to 
other neighbors. A BGP speaker can set, append, or modify the community of a route when learning, 
advertising, or redistributing routes. When routes are aggregated, the resulting aggregate has a 
COMMUNITIES attribute that contains all communities from all the initial routes.

You can use community lists to create groups of communities to use in a match clause of a route map. 
As with an access list, a series of community lists can be created. Statements are checked until a match 
is found. As soon as one statement is satisfied, the test is concluded.

To set the COMMUNITIES attribute and match clauses based on communities, see the match 
community-list and set community route-map configuration commands in the 

.

By default, no COMMUNITIES attribute is sent to a neighbor. You can specify that the COMMUNITIES 
attribute be sent to the neighbor at an IP address by using the neighbor send-community router 
configuration command.

Beginning in privileged EXEC mode, follow these steps to create and to apply a community list:

Enter global configuration mode.

ip community-list community-list-number 
{permit | deny} community-number

Create a community list, and assign it a number.

The community-list-number is an integer from 1 to 99 that 
identifies one or more permit or deny groups of communities.

The community-number is the number configured by a set 
community route-map configuration command.

router bgp autonomous-system

Enter BGP router configuration mode.

neighbor {ip-address | peer-group name} 
send-community 

Specify that the COMMUNITIES attribute be sent to the neighbor at 
this IP address.

set comm-list list-num delete

(Optional) Remove communities from the community attribute of an 
inbound or outbound update that match a standard or extended 
community list specified by a route map.

Return to global configuration mode.