User's Manual

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459
Users Manual of CS-6306R
Refer to the section “BGP Route Aggregation Example”.
45.4.2.2.3 Configuring BGP Community Attribute
The routing policy that BGP supports is based one of the following three values for BGP routing information:
Routing network number
Value of the AS_PATH attribute
Value of the COMMUNITY attribute
Routes can be classified into the community through the COMMUNITY attribute and the community-based
routing policy can be applied to routes. Therefore, the configuration of routing information control is simplified.
Community is a group of routes having the same attributes. Each route may belong to multiple communities.
The AS administrator can decide which community a route belongs to.
The COMMUNITY attribute is an optional, transmissible and global, which ranges from 1 to 4,294,967,200.
The famous communities that are predefined in the Internet are listed in the following table:
Community Description
no-export Does not broadcast the route to the EBGP peers,
including the EBGP peers in the autonomous
system.
no-advertise Does not broadcast the route to any peer.
local-as Does not broadcast the route to the outside of the
autonomous system.
When generating, receiving or forwarding the route, the BGP session sponsor can set, add or modify the
route community attributes. After the routes are aggregated, the aggregation contains the COMMUNITY
attribute from all original routes.
The COMMUNITY attribute is not sent to neighbors by default. Run the following command to send the
COMMUNITY attribute to the designated neighbor.
Command Purpose
neighbor {ip-address }
send-community
Sends the COMMUNITY attribute to the
designated neighbor.
Perform the following operations to set the community attribute:
Command Purpose
route-map map-name
sequence-number {deny | permit}
Configures the route map.
set community community-value
Configures the setup regulations.
router bgpautonomous-system
Enters the router configuration mode.
neighbor {ip-address }
route-mapaccess-list-name {in | out }
Applies the route map.