Date created: 03/29/13 13:10:50. Last modified: 09/25/17 11:54:03

BGP Dampening

http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfbgp.html#wp1002395

Half-life—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). The process of reducing the penalty happens every 5 seconds.

Reuse limit—As the penalty for a flapping route decreases and falls below this reuse limit, the route is unsuppressed. That is, the route is added back to the BGP table and once again used for forwarding. The default reuse limit is 750. The process of unsuppressing routes occurs at 10-second increments. Every 10 seconds, the router finds out which routes are now unsuppressed and advertises them to the world.

Suppress limit—A route is suppressed when its penalty exceeds this limit. The default value is 2000.

Maximum suppress limit—This value is the maximum amount of time a route can be suppressed. The default value is four times the half-life.

Router(config)# bgp dampening !Enables BGP route dampening.
Router(config-router)#bgp dampening 15 1000 3000 60

! <1-45>     Half-life time for the penalty (in minutes)
! <1-20000>  Value to start reusing a route
! <1-20000>  Value to start suppressing a route
! <1-255>  Maximum duration to suppress a stable route (4*Half Life)

From RIPE-580: In order to punish the biggest offenders - those preWixes that Wlap the most - yet without punishing others, the RIPE Routing-WG recommends vendors raise the maximum suppress threshold in router implementations to 50,000 and operators conWigure a suppress threshold value of at least 6,000. The vendors might also change the default suppress threshold to 6,000. But this might surprise operators who use the default.

http://www.ripe.net/ripe/docs/ripe-580