Configuring Route Flap Dampening - Dell PowerConnect B-RX Configuration Manual

Commands for Router D
BigIron RXD(config)# router bgp
BigIron RXD(config-bgp)# local-as 64513
BigIron RXD(config-bgp)# confederation identifier 10
BigIron RXD(config-bgp)# confederation peers 64512 64513
BigIron RXD(config-bgp)# write memory

Configuring route flap dampening

Route Flap Dampening reduces the amount of change propagated by BGP due to routing state
caused by unstable routes. Reducing change propagation will help reduce processing
requirements.
To enable route flap dampening using the default values, enter the following command.
BigIron RX(config-bgp)# dampening
Syntax: dampening [<half-life> <reuse> <suppress> <max-suppress-time>]
The <half-life> parameter specifies the number of minutes after which the route's 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's 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 – 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's penalty can become before the device
suppresses the route. You can set the suppression threshold to a value from 1 – 20000. The
default is 2000 (more than 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 – 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.
BigIron RX(config-bgp)# 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.
BigIron RX Series Configuration Guide
53-1001810-01
Configuring route flap dampening
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