для Cisco Cisco IOS Software Release 12.2(1)T

To use SPF throttling, you should understand the following concepts:

SPF calculations occur at the interval set by the timers throttle spf command. The wait interval 
indicates the amount of time to wait until the next SPF calculation occurs. Each wait interval after that 
calculation is twice as long as the previous one until the wait interval reaches the maximum wait time 
specified. 

The SPF timing can be better explained using an example. In this example the start interval is set at 5 
milliseconds (ms), the wait interval at 1000 milliseconds, and the maximum wait time is set at 90,000 
milliseconds.

timers throttle spf 5 1000 90000

 shows the intervals at which the SPF calculations occur so long as at least one topology change 

event is received in a given wait interval.

Notice that the wait interval between SPF calculations doubles when at least one topology change event 
is received during the previous wait interval. Once the maximum wait time is reached, the wait interval 
remains the same until the topology stablizes and no event is received in that interval.

If the first topology change event is received after the current wait interval, the SPF calculation is 
delayed by the amount of time specified as the start interval. The subsequent wait intervals continue to 
follow the dynamic pattern.

If the first topology change event occurs after the maximum wait interval begins, the SPF calculation is 
again scheduled at the start interval and subsequent wait intervals are reset according the parameters 
specified in the timers throttle spf command. Notice in 

 that a topology change event was 

received after the start of the maximum wait time interval and that the SPF intervals have been reset.