199
Figure 55 BGP route dampening
• Peer group
You can organize BGP peers with the same attributes into a group to simplify their
configurations.
When a peer joins the peer group, the peer obtains the same configuration as the peer group. If
the configuration of the peer group is changed, the configuration of group members is changed.
• Community
You can apply a community list or an extended community list to a routing policy for route
control. For more information, see "BGP path attributes."
• Route reflector
IBGP peers must be fully meshed to maintain connectivity. If n routers exist in an AS, the
number of IBGP connections is n(n-1)/2. If a large number of IBGP peers exist, large amounts
of network and CPU resources are consumed to maintain sessions.
Using route reflectors can solve this issue. In an AS, a router acts as a route reflector, and other
routers act as clients connecting to the route reflector. The route reflector forwards routing
information received from a client to other clients. In this way, all clients can receive routing
information from one another without establishing BGP sessions.
A router that is neither a route reflector nor a client is a non-client, which, as shown in Figure 56,
must establish BGP sessions to the route reflector and other non-clients.
Figure 56 Network diagram for a route reflector
Suppress
threshold
Reusable
threshold
Penalty
value
Time
Half-life
Suppression time
Client
Client Client
Route reflector
Non-client
Non-client
Cluster
AS 65000
IBGP
IBGP
IBGP
IBGP
IBGP
IBGP
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