Router 2

Router 1 is configured by:

The following displays route dampening statistics for network 1.0.0.0/8 prior to any instability:

System(su-config)->show ip bgp 1.0.0.0/8 detail
Route status codes: > - active
    Network                  Next Hop              Rib MED Local-Pref Origin AS Path
>   1.0.0.0/8                192.168.12.111        U   0      100    Inc     10
Community attributes in route:
Extended Community attributes in route:
Route Flap Dampening configuration file name: flap1
Is route suppressed? No
Flap penalty: 0, Flap Count 0, Flap time remaining 0 seconds
System(su-config)->

If you were to enter the show command immediately after the first flap, the route flap dampening statistics would show:

System(su-config)->show ip bgp 1.0.0.0/8 detail
Route status codes: > - active
...
Route Flap Dampening configuration file name: flap1
Is route suppressed? No
Flap penalty: 99, Flap Count 1, Flap time remaining 0 seconds

The route remains unsuppressed because the route penalty has not exceeded the cutoff value. The flap penalty has decayed by 1 point from 100 to 99 since the route flap occurred. The flap count is 1 and because the route has not yet been suppressed, flap time is set to 0 seconds.

Entering the show command immediately after the second route flap, the route flap dampening statistics would show:

System(su-config)->show ip bgp 1.0.0.0/8 detail
Route status codes: > - active
...
Route Flap Dampening configuration file name: flap1
Is route suppressed? Yes
Flap penalty: 185, Flap Count 2, Flap time remaining 295 seconds

Because the flap penalty exceeds the cutoff setting, route flap dampening has suppressed the route. Flap time now displays the amount of seconds remaining before the hold-time is reached.

After waiting the 5 minute hold-time, the display shows that the route has been unsuppressed. If the hold-time was set to the default value of 900 seconds, and no other router flaps occurred for this route, the route penalty would have decayed to the point that the route would have been unsuppressed when the route penalty reached the reuse setting of 75.

System(su-config)->show ip bgp 1.0.0.0/8 detail
Route status codes: > - active
...
Route Flap Dampening configuration file name: flap1
Is route suppressed? No
Flap penalty: 86, Flap Count 2, Flap time remaining 0 seconds

Configuring BGP Flap Dampening describes how to configure the BGP flap dampening.

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Configuring BGP Flap Dampening

Step Task Command(s)
1 In router configuration mode, enter the dampen flap command mode for the named dampen flap table. dampen-flap name
2 In BGP flap dampening configuration mode, optionally modify the route suppression threshold. cutoff threshold
3 In BGP flap dampening configuration mode, optionally modify the time in seconds after which a reachable route‘s penalty value decays to half of its current value. half-life-reach seconds
4 In BGP flap dampening configuration mode, optionally modify the time in seconds after which an unreachable route‘s penalty value decays to half its current value. half-life-reach seconds
5 In BGP flap dampening configuration mode, optionally modify the maximum time a route can be suppressed. hold-time seconds
6 In BGP flap dampening configuration mode, optionally modify the decay memory limit for reachable routes. memory-limit-reach seconds
7 In BGP flap dampening configuration mode, optionally modify the decay memory limit for unreachable routes. memory-limit-reach seconds
8 In BGP flap dampening configuration mode, optionally modify the route penalty value below which a suppressed route is reused. reuse value