Cisco 3845 - Security Bundle Router Software Manual page 620
Software configuration guide
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Configuring BGP
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:
•
•
•
•
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
Redistribute Routing Information" section on page
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:
Command
Step 1
configure terminal
Step 2
ip community-list community-list-number
{permit | deny} community-number
Step 3
router bgp autonomous-system
Step 4
neighbor {ip-address | peer-group name}
send-community
Step 5
set comm-list list-num delete
Step 6
exit
Step 7
ip bgp-community new-format
Step 8
end
Cisco ME 3800X and 3600X Switch Software Configuration Guide
29-54
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.
29-97.
Purpose
Enter global configuration mode.
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.
Enter BGP router configuration mode.
Specify that the COMMUNITIES attribute be sent to the neighbor at
this IP address.
(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.
(Optional) Display and parse BGP communities in the format AA:NN.
A BGP community is displayed in a two-part format 2 bytes long. The
Cisco default community format is in the format NNAA. In the most
recent RFC for BGP, a community takes the form AA:NN, where the
first part is the AS number and the second part is a 2-byte number.
Return to privileged EXEC mode.
Chapter 29
Configuring IP Unicast Routing
"Using Route Maps to
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