Setting the SPF Calculation Interval

Context

A network change always triggers IS-IS to perform SPF calculation. Frequent SPF calculation will consume excessive CPU resources, affecting services.

To solve this problem, configure an intelligent timer to control the interval for SPF calculation. For example, to speed up IS-IS route convergence, set the interval for SPF calculation to a small value and set the interval to a large value after the IS-IS network becomes stable.

Procedure

Run system-view
The system view is displayed.
Run isis [ process-id ]
The IS-IS view is displayed.
Run timer spf max-interval [ init-interval [ incr-interval ] ]
The SPF intelligent timer is configured.

By default, no SPF intelligent timer is configured and the maximum delay in SPF calculation is 5 seconds.
The intelligent timer changes as follows:
- The delay in the first SPF calculation is determined by init-interval; the delay in the second SPF calculation is determined by incr-interval. From the third time on, the delay in SPF calculation increases twice every time until the delay reaches the value specified by max-interval. After the delay remains at the value specified by max-interval for three times or the IS-IS process is restarted, the delay decreases to the value specified by init-interval.
- If incr-interval is not specified, the delay in SPF calculation for the first time is determined by init-interval. From the second time on, the delay in SPF calculation is determined by max-interval. After the delay remains at the value specified by max-interval for three times or the IS-IS process is restarted, the delay decreases to the value specified by init-interval.
- When only max-interval is specified, the intelligent timer functions as an ordinary one-time triggering timer.
(Optional) Run spf-slice-size duration-time
The maximum duration for SPF calculation is configured.

By default, IS-IS route calculation lasts for a maximum of 2 ms at a time.