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Chapter 32
Configuring IP Unicast Routing
Command
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.
Beginning in privileged EXEC mode, use these commands to configure BGP route dampening:
Command
Step 1
configure terminal
Step 2
router bgp autonomous-system
Step 3
bgp dampening
Step 4
bgp dampening half-life reuse suppress
max-suppress [route-map map]
Step 5
end
Step 6
show ip bgp flap-statistics [{regexp regexp} |
{filter-list list} | {address mask [longer-prefix]}]
Step 7
show ip bgp dampened-paths
Step 8
clear ip bgp flap-statistics [{regexp regexp} |
{filter-list list} | {address mask [longer-prefix]}
Step 9
clear ip bgp dampening
Step 10
copy running-config startup-config
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.
78-17058-01
Purpose
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.
Purpose
Enter global configuration mode.
Enter BGP router configuration mode.
Enable BGP route dampening.
(Optional) Change the default values of route dampening
factors.
Return to privileged EXEC mode.
(Optional) Monitor the flaps of all paths that are flapping. The
statistics are deleted when the route is not suppressed and is
stable.
(Optional) Display the dampened routes, including the time
remaining before they are suppressed.
(Optional) Clear BGP flap statistics to make it less likely that a
route will be dampened.
(Optional) Clear route dampening information, and unsuppress
the suppressed routes.
(Optional) Save your entries in the configuration file.
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
Configuring BGP
32-57
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