BGP dampening

Instability in the BGP domain causes BGP router send the routing updates to its BGP peers. Every time BGP router receives an update it re-calculate its best path. Due to BGP router contains a large number of routes in its routing table, the router need to use a lot of CPU resource and memory to calculate it. If there is a route flap in the network, it will make it worse since router needs to do a recalculation for many times.


Dampening is the feature in Cisco IOS preventing BGP router calculates a large number of routes updates when the route flap. BGP process assigns a penalty to the route each time it flaps. When the penalty exceeds the limit, the route is dampened. It will not accept or announce any routing update from other peer. The penalty decays at the half life rate.


BGP dampening command.


bgp dampening [half-life reuse suppress max-suppress-time] [route-map map-name]

Example

router bgp 10

bgp dampening 30 1500 10000 120