Configure BGP GR

Graceful Restart (GR) is used in active/standby switchover between devices. During the GR, the routing information of the local device and neighbor devices keep unchanged at the forwarding layer, and data forwarding is not affected. After the switchover is completed and the new device starts to run, the two devices synchronize routing information at the protocol layer and update the forwarding layer so that data forwarding is not interrupted during the device switchover process.

Roles involved in a GR:

• GR Restarter: It is the device that is gracefully restarted.
• GR Helper: It is the device that helps with the GR.
• GR Time: It is the maximum time for GR-Restarters to restart. GR Helper maintains the stability of routes during the period of time.

A dual-controller device can act as a GR Restarter and a GR Helper, while a centralized device can only act as a GR Helper, helping the GR Restarter to complete a GR. When the GR Restarter is in the GR process, the GR Helper maintains the route stability until GR Time timeout. After the GR Helper helps with the GR, it synchronizes route information. During the process, network routes and packet forwarding keep the status before the GR, effectively ensuring the network stability.

The BGP GR relation is set up through OPEN packet negotiation when a connection is set up between neighbors. When the GR Restarter restarts the neighbor, the BGP session will be disconnected, but the routes that are learnt from the neighbor are not deleted. The routes are still normally forwarded in the IP routing table. The routes are labeled with the Stale marks only in the BGP routing table. After the GR is completed, the routes will be refreshed.

The GR Restarter needs to set up a connection with the GR Helper within the maximum allowed time; otherwise, the GR Helper with cancel the maintained GR route and cancel the GR process. After the neighbor is re-connected, the GR Helper needs to receive an update packet with the End-Of-RIB mark from the GR Restarter to complete the GR process; otherwise, the GR route that is not updated will be deleted after the maximum hold time (stalepath-time) expires, and then the GR relation is released.

Configuration Condition

Before configuring a BGP GR, ensure that:

• BGP is enabled.
• BGP neighbors are configured and a session is set up successfully.

Configure BGP GR Restarter

Table 12-44 Configure BGP GR Restarter

Configure a BGP GR Helper

Table 12-45 Configure a BGP GR helper