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PowerConnect B-Series FCX Configuration Guide 1055
53-1002266-01
Configuring route flap dampening
30
Globally configuring route flap dampening
To enable route flap dampening using the default values, enter the following command.
PowerConnect(config-bgp-router)#dampening
Syntax: dampening [<half-life> <reuse> <suppress> <max-suppress-time>]
The <half-life> parameter specifies the number of minutes after which the route penalty becomes
half its value. The route penalty allows routes that have remained stable for a while despite earlier
instability to eventually become eligible for use again. The decay rate of the penalty is proportional
to the value of the penalty. After the half-life expires, the penalty decays to half its value. Thus, a
dampened route that is no longer unstable can eventually become eligible for use again. You can
configure the half-life to be from 1 - 45 minutes. The default is 15 minutes.
The <reuse> parameter specifies how low a route penalty must become before the route becomes
eligible for use again after being suppressed. You can set the reuse threshold to a value from 1
through 20000. The default is 750 (0.75, or three-fourths, of the penalty assessed for a one
“flap”).
The <suppress> parameter specifies how high a route penalty can become before the Layer 3
Switch suppresses the route. You can set the suppression threshold to a value from 1 through
20000. The default is 2000 (two “flaps”).
The <max-suppress-time> parameter specifies the maximum number of minutes that a route can
be suppressed regardless of how unstable it is. You can set the maximum suppression time to a
value from 1 through 20000 minutes. The default is four times the half-life setting. Thus, if you use
the default half-life of 15 minutes, the maximum suppression time is 60 minutes.
The following example shows how to change the dampening parameters.
PowerConnect(config-bgp-router)#dampening 20 200 2500 40
This command changes the half-life to 20 minutes, the reuse threshold to 200, the suppression
threshold to 2500, and the maximum number of minutes a route can be dampened to 40.
NOTE
To change any of the parameters, you must specify all the parameters with the command. If you want
to leave some parameters unchanged, enter their default values.
Using a route map to configure route flap dampening
for specific routes
Route maps enable you to fine tune route flap dampening parameters for individual routes. To
configure route flap dampening parameters using route maps, configure BGP4 address filters for
each route you want to set the dampening parameters for, then configure route map entries that
set the dampening parameters for those routes. The following sections show examples.
To configure address filters and a route map for dampening specific routes, enter commands such
as the following.