13.4.8 Route flap dampening

Route flap dampening minimizes network instability by temporarily suppressing the use of routes that flap frequently. Note that this functionality is not supported in VRFs. The following table describes the parameters used in route flap dampening.

Table 13-11: Components of the route flap dampening facility
Parameters	Description
Penalty	A dynamic control variable for suppressing or reusing the route. The penalty value increases with each route flap, and decreases with time. The penalty is incremented by 1 every time a route flaps (becomes unreachable) and is decremented based on the half-life time. The maximum penalty value is calculated as follows: maximum-penalty = reuse-limit x 2^(maximum-suppression-time/half-life-time)
Suppress limit	Use of the route is suppressed when the penalty reaches or exceeds this value.
Reuse limit	Use of the route is allowed when the penalty falls to this value or lower.
Half-life time	The time required for the penalty to be reduced to half (50%).
Maximum suppress time	The maximum duration for the suppression of a route. This value is the time taken for the penalty value to decrease from the maximum to the reuse limit.

The following figure illustrates how route flap dampening operates.

Figure 13-22: Route flap dampening behavior