OSPF: SPF Throttling

In networks where  there are links that can bounce often, this could cause the SPF algorithm to recalculate the best path often causing unnecessary strain on the processor of the router.  To make this calculation more efficient in scenarios such as this, you can tune OSPF to run the SPF algorithm in intervals as opposed to immediate link state changes.

The scheduling of SPF runs is controlled by a feature called SPF throttling, there are three parameters of this feature that define the length of time between SPF runs.

spf-start
spf-hold
spf-max-wait

spf-start defines the wait interval before SPF computation.

spf-hold parameter defines the wait time between subsequent SPF runs and its value doubles for each consecutive SPF run

spf-max-wait defines the maximum time between two SPF runs and also defines how long the network must be stable before the interval is reset back to the spf-start and spf-hold pre-configured values.

 

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