Changing the SPF timer

Every IS maintains a Shortest Path First (SPF) tree, which is a representation of the states of each of the IS‘s links to ESs and other ISs. If the IS is both a Level-1 and Level-2 IS, it maintains separate SPF trees for each level. To ensure that the SPF tree remains current, the IS updates the tree at regular intervals following a change in network topology or the link state database. This task changes the maximum interval in seconds between SPF recalculations, the initial SPF calculation delay, and the hold time between the first and second SPF calculation.

About this task

Procedure

Enter the configure terminal command to access global configuration mode.
```
device# configure terminal
```
Enter the router isis command to enter IS-IS router configuration mode and enable IS-IS on the device.
```
device(config)# router isis
```
Enter the spf-interval command with the level-1 parameter, specifying values for the max-wait , initial-wait , and second-wait parameters, to set the maximum interval in seconds between SPF recalculations, the initial SPF calculation delay, and the hold time between the first and second SPF calculation.
```
device(config-isis-router)# spf-interval level-1 15 10000 15000
```

Example

The following example specifies that the maximum interval in seconds between SPF recalculations is 15 seconds for Level 1 packets. The initial SPF calculation delay is 10000 milliseconds and the hold time between the first and second SPF calculation is 15000 millseconds.

device# configure terminal
device(config)# router isis
device(config-isis-router)# spf-interval level-1 15 10000 15000