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Catalyst 3750 MetroSwitch Software Configuration Guide
78-15870-01
Chapter 28 Configuring IP Unicast Routing
Configuring BGP
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.
Beginning in privileged EXEC mode, use these commands to configure BGP route dampening:
To disable flap dampening, use the no bgp dampening router configuration command without
keywords. To set dampening factors back to the default values, use the no bgp dampening router
configuration command with values.
Step 5
no bgp client-to-client reflection (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.
Step 6
end Return to privileged EXEC mode.
Step 7
show ip bgp Verify the configuration. Display the originator ID and the
cluster-list attributes.
Step 8
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
router bgp autonomous-system Enter BGP router configuration mode.
Step 3
bgp dampening Enable BGP route dampening.
Step 4
bgp dampening half-life reuse suppress
max-suppress [route-map map]
(Optional) Change the default values of route dampening
factors.
Step 5
end Return to privileged EXEC mode.
Step 6
show ip bgp flap-statistics [{regexp regexp} |
{filter-list list} | {address mask [longer-prefix]}]
(Optional) Monitor the flaps of all paths that are flapping. The
statistics are deleted when the route is not suppressed and is
stable.
Step 7
show ip bgp dampened-paths (Optional) Display the dampened routes, including the time
remaining before they are suppressed.
Step 8
clear ip bgp flap-statistics [{regexp regexp} |
{filter-list list} | {address mask [longer-prefix]}
(Optional) Clear BGP flap statistics to make it less likely that a
route will be dampened.
Step 9
clear ip bgp dampening (Optional) Clear route dampening information, and unsuppress
the suppressed routes.
Step 10
copy running-config startup-config (Optional) Save your entries in the configuration file.
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