Policy-Based Route Flap Dampening

You can use policy-based route flap dampening to apply different dampening criteria to different routes. Establish one or more match clauses for an instance of a route map. Then use the set dampening command to specify the dampening values that apply to routes that pass all the match clauses for that route map. Consider the following example:

Access list 1 permits routes that originate in AS 300. Instance 5 of route map 21 permits routes that match access list 1 and applies the set of dampening criteria to only those routes; in this case, routes that originate in AS 300.

You can restore the advertisement of routes suppressed as a result of policy-based route flap dampening by issuing the neighbor unsuppress-map command. You can unsuppress routes from a specified neighbor or peer group. You must specify a route map; only those routes that match the route map are unsuppressed.

neighbor unsuppress-map

• Use to unsuppress routes that have been suppressed by a set dampening clause in a route map.
• If you specify a BGP peer group by using the peerGroupName argument, all the members of the peer group inherit the characteristic configured with this command. You cannot override this inheritance for a peer group member.
• Routes previously suppressed by a route map that are unsuppressed by this command are not automatically advertised; you must use the clear ip bgp command to perform a hard clear or outbound soft clear.
• Example

  host1(config-router)#neighbor berlin5 unsuppress-map inmap3

• Use the no version to restore the default values.
• See neighbor unsuppress-map.

set dampening

• Use to enable BGP route flap dampening only on routes that pass the match clauses of, and are redistributed by, a particular route map.
• BGP creates a dampening parameter block for each unique set of dampening parameters—such as suppress threshold and reuse threshold—used by BGP. For example, if you have a route map that sets the dampening parameters to one set of values for some routes and to another set of values for the remaining routes, BGP uses and stores two dampening parameter blocks, one for each set.
• Example

  host1(config)#route-map nyc1 permit 10

  host1(config-route-map)#set dampening 5 1000 1500 45 15

• Use the no version to delete the set clause from a route map.
• See set dampening.

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