Behavior is different for outbound policies configured for peer groups for which
you have enabled Adj-RIBs-Out. If you change the outbound policy for such a
peer group and want to fill the Adj-RIBs-Out table for that peer group with the
results of the new policy, you must use the clear ip bgp peer-group command
to perform a hard clear or outbound soft clear of the peer group. You cannot
merely perform a hard clear or outbound soft clear for individual peer group
members because that causes BGP to resend only the contents of the Adj-RIBs-Out
table.
■ Use the no version to send only standard communities to a BGP neighbor. Use
the default version to remove the explicit configuration from the peer or peer
group and reestablish inheritance of the feature configuration.
■ See neighbor send-community.
set community
■ Use to set the community attribute in BGP updates.
■ You can specify a community list number in the range 1–4294967295, or in the
new community format of AA:NN, or one of the following well-known
communities:
■ local-as—Prevents advertisement outside the local AS
■ no-advertise—Prevents advertisement to any peer
■ no-export—Prevents advertisement beyond the BGP confederation boundary
■ Alternatively, you can use the list keyword to specify the name of a community
list that you previously created with the ip community-list command.
■ Example
host1(config)#route-map nyc1 permit 10
host1(config-route-map)#set community no-advertise
■ Use the none keyword to remove the community attribute from a route.
■ Use the no version to delete the set clause from a route map.
■ See set community.
Community Lists
A community list is a sequential collection of permit and deny conditions. Each
condition describes the community number to be matched. If you issued the ip
bgp-community new-format command, the community number is in AA:NN format;
otherwise it is in decimal format.
The router tests the community attribute of a route against the conditions in a
community list one by one. The first match determines whether the router accepts
(the route is permitted) or rejects (the route is denied) a route having the specified
community. Because the router stops testing conditions after the first match, the
order of the conditions is critical. If no conditions match, the router rejects the route.
Consider the network structure shown in Figure 27 on page 96.
Configuring BGP Routing Policy ■ 95
Chapter 1: Configuring BGP Routing
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