The timer spf command configures the SPF calculation delay.
The undo timer spf command restores the default value.
By default, the maximum SPF calculation delay is 5 seconds.
| Parameter | Description | Value |
|---|---|---|
| max-interval | Specifies the maximum SPF calculation delay. | The value is an integer that ranges from 1 to 120, in seconds. By default, it is 5 seconds. |
| init-interval | Specifies the initial SPF calculation delay. | The value is an integer that ranges from 1 to 60000 milliseconds. By default, it is 50 milliseconds. |
| incr-interval | Specifies the ascending delay between two times of route calculation. | It is an integer that ranges from 1 to 60000 milliseconds. By default, it is 200 milliseconds. |
This command is valid for all topologies in an IS-IS process.
For IS-IS , when the LSDB is changed, SPF calculation is required. However, if the SPF calculation is performed too frequently, the system efficiency will be lowered and a great number of resources on the system will be occupied. To delay SPF calculation can improve route calculation efficiency to some degree. On the other hand, if the delay time for route calculation is too long, the route convergence becomes slow.
To accelerate the route convergence speed and not to affect the efficiency of routers, the intelligent timer is used during the SPF calculation. The intelligent timer can adjust the delay time according to the change frequency of the LSDB.
When SPF calculation is performed for the first time, the interval is init-interval. Each time a route changes, the interval is added by incr-interval until the interval reaches max-interval. After max-interval expires without flapping or the IS-IS process is restarted, the delay decreases to init-interval.
When incr-interval is not used and the SPF calculation is performed for the first time, init-interval is used as the initial delay time for SPF calculation. Then, the delay time for SPF calculation is max-interval. After the delay reaches max-interval for three times or the IS-IS process is reset, the delay time is reduced to init-interval.
When only max-interval is used, the intelligent timer becomes a one-short triggered timer.