Graceful-restart is a feature that allows BGP neighbors to maintain their routing information during a BGP restart or failover event, without disrupting traffic forwarding or causing route flaps. Graceful-restart works by allowing a BGP speaker (the restarting router) to notify its neighbors (the helper routers) that it is about to restart or failover, and request them to preserve their routing information and forwarding state for a certain period of time (the restart time). The helper routers then mark the routes learned from the restarting router as stale, but keep them in their routing table and continue forwarding traffic based on them until they receive an end-of-RIB marker from the restarting router or until the restart time expires. This way, graceful-restart can minimize traffic disruption and routing instability during a BGP restart or failover event. Reference: https://docs.fortinet.com/document/fortigate/7.0.0/cookbook/19662/bgp-graceful-restart