Configuring Route Dampening - Cisco Catalyst 3750-X Software Configuration Manual

Configuring BGP
When the route reflector receives an advertised route, it takes one of these actions, depending on the
neighbor:
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•
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Usually a cluster of clients have a single route reflector, and the cluster is identified by the route reflector
router ID. To increase redundancy and to avoid a single point of failure, a cluster might have more than
one route reflector. In this case, all route reflectors in the cluster must be configured with the same 4-byte
cluster ID so that a route reflector can recognize updates from route reflectors in the same cluster. All
the route reflectors serving a cluster should be fully meshed and should have identical sets of client and
nonclient peers.
Beginning in privileged EXEC mode, use these commands to configure a route reflector and clients:
Command
Step 1
configure terminal
Step 2 router bgp autonomous-system
neighbor ip-address | peer-group-name
Step 3
route-reflector-client
Step 4 bgp cluster-id cluster-id
Step 5
no bgp client-to-client reflection
Step 6 end
Step 7 show ip bgp
Step 8
copy running-config startup-config

Configuring Route Dampening

Route flap dampening is a BGP feature designed to minimize the propagation of flapping routes across
an internetwork. A route is considered to be flapping when it is repeatedly available, then unavailable,
then available, then unavailable, and so on. When route dampening is enabled, a numeric penalty value
is assigned to a route when it flaps. When a route's accumulated penalties reach a configurable limit,
BGP suppresses advertisements of the route, even if the route is running. The reuse limit is a
configurable value that is compared with the penalty. If the penalty is less than the reuse limit, a
suppressed route that is up is advertised again.
Dampening is not applied to routes that are learned by IBGP. This policy prevents the IBGP peers from
having a higher penalty for routes external to the AS.
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
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A route from an external BGP speaker is advertised to all clients and nonclient peers.
A route from a nonclient peer is advertised to all clients.
A route from a client is advertised to all clients and nonclient peers. Hence, the clients need not be
fully meshed.
Purpose
Enter global configuration mode.
Enter BGP router configuration mode.
Configure the local router as a BGP route reflector and the
specified neighbor as a client.
(Optional) Configure the cluster ID if the cluster has more than
one route reflector.
(Optional) Disable client-to-client route reflection. By default,
the routes from a route reflector client are reflected to other
clients. However, if the clients are fully meshed, the route
reflector does not need to reflect routes to clients.
Return to privileged EXEC mode.
Verify the configuration. Display the originator ID and the
cluster-list attributes.
(Optional) Save your entries in the configuration file.
Chapter 42 Configuring IP Unicast Routing
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