892 OSPF CommandsSyntaxnsf [ ietf ] [ planned-only ]no nsf [ietf]ietf — This keyword is used to distinguish the IETF standardimplementation of graceful restart from other implementations. Since theIETF implementation is the only one supported, this keyword is optional.planned-only — This keyword indicates that OSPF should only perform agraceful restart when the restart is planned (i.e., when the restart is a result ofthe initiate failover command).Default ConfigurationGraceful restart is disabled by defaultCommand ModeRouter OSPF Configuration modeUser GuidelinesGraceful restart works in concert with nonstop forwarding to enable thehardware to continue forwarding IPv4 packets using OSPFv2 routes while abackup unit takes over management unit responsibility. When OSPFexecutes a graceful restart, it informs its neighbors that the OSPF controlplane is restarting, but that it will be back shortly. Helpful neighbors continueto advertise to the rest of the network that they have full adjacencies with therestarting router, avoiding announcement of a topology change andeverything that goes with that (i.e., flooding of LSAs, SPF runs). Helpfulneighbors continue to forward packets through the restarting router. Therestarting router relearns the network topology from its helpful neighbors.This implementation of graceful restart restarting router behavior is onlyuseful with a router stack. Graceful restart does not work on a standalone,single-unit router.Example–
