guruprasadr Fri, 12/26/2008 - 00:22

HI Rupesh, [Pls RATE if HELPS]


router(config)#bgp dampening

router(config)#bgp dampening 20 1800 8000 50


The following example enables route dampening and sets the half-life-time to 20 minutes, the reuse-value to 1800, the suppress-value to 8000, and the maximum-suppress-time to 50 minutes.


Hope I am Informative. Pls RATE if HELPS


Best Regards,


Guru Prasad R

Rupesh Kashyap Fri, 12/26/2008 - 01:16

yes, you are right. I only could not understand "half-life-time". Once the route

has been assigned a penalty, the penalty is decreased by half after the half-life

period (which is 15 minutes by default). I am unable to understand this. Please help.

guruprasadr Fri, 12/26/2008 - 01:35

HI Rupesh, [Pls RATE if HELPS]


A penalty of 1000 is assessed each time the route fails. When the penalties reach a predefined threshold (suppress-value), the router stops advertising the route.


Once a route is assessed a penalty, the penalty is decreased by half each time a predefined amount of time elapses (half-life-time).

Half-life-time -The range is 1-45 minutes, and the current default is 15 minutes.


When the accumulated penalties fall below a predefined threshold (reuse-value), the route is unsuppressed and added back into the BGP routing table.


Hope I am Informative. Pls RATE if HELPS


Best Regards,


Guru Prasad R

Rupesh Kashyap Fri, 12/26/2008 - 01:47

What is the meaning of "the penalty is decreased by half each time a predefined amount of time elapses "

guruprasadr Fri, 12/26/2008 - 01:58

HI Rupesh, [Pls RATE if HELPS]


The Route Dampening Process:


A route that is flapping receives a penalty of 1000 for each flap. When the accumulated penalty reaches a configurable limit, BGP suppresses advertisements of the route even if the route is announced. The accumulated penalty is decremented by the half-life time. When the accumulated penalty is less than the reuse limit, the route is advertised again if it has not been withdrawn.


For example, a route with a penalty of 3000 will take the half-life time of 15 minutes to cut the penalty in half and reach the reuse penalty of 1500, at which point the route will be advertised again. Similarly, a route with a penalty of 6000 will take 15 minutes to cut the penalty in half and reach a penalty of 3000. It will then an additional 15 minutes to cut the penalty in half again and reach the reuse penalty of 1500. The total decay time from 6000 to 1500 (i.e., reuse) with a half-life time of 15 will be 30 minutes. Please see "RFC 2439" for more details.


Hope I am Informative.


Pls RATE if HELPS


Best Regards,


Guru Prasad R

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