Configuring Graceful Restart for ISIS-SPB
![[IMPORTANT: ]](images/important.png) | IMPORTANT: Graceful Restart and IS-IS NSR are mutually exclusive. You cannot use both features on the device. | |
Graceful Restart ensures nonstop forwarding while ISIS-SPB processes are re-establishing their adjacency after SPBM is re-enabled or an active/standby switchover is performed.
Graceful Restart enables a restarting node (the GR restarter) to quickly recover its SPBM topology, routing, and session information from a neighbor (the GR helper). During the GR process, the GR helper maintains the adjacency with the GR restarter.
Typically, you only need to configure Graceful Restart on the GR restarter. As a best practice, configure Graceful Restart on an SPBM node if it is the only feature available on the node to ensure nonstop forwarding.
To configure Graceful Restart for ISIS-SPB:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter SPBM view. | spbm | N/A |
3. Enable Graceful Restart for ISIS-SPB. | graceful-restart | By default, ISIS-SPB Graceful Restart is disabled. |
4. (Optional.) Set the SA bit in ISIS-SPB hello PDUs. | undo graceful-restart suppress-sa | By default, the Suppress-Advertisement (SA) bit is set. Setting the SA bit prevents the neighbor from advertising the ISIS-SPB adjacency with the GR restarter. This setting prevents route blackholes by temporarily excluding the restarter from the SPF computation on other SPBM nodes. If the SA bit is not set, the ISIS-SPB neighbors advertise the ISIS-SPB adjacency with the device while the device is restarting. |
5. (Optional.) Set the T2 timer. | graceful-restart t2 t2-value | The default T2 timer is 300 seconds for ISIS-SPB Graceful Restart. The device advertises the T2 timer as the adjacency hold time to its neighbor during a GR process. Before the timer expires, the neighbor maintains the adjacency with the device. If the device fails to complete the restart before this timer expires, the neighbor removes the adjacency. |