1142 OSPF Commandsuntil the graceful restart completes. By exiting the graceful restart on atopology change, a router tries to eliminate the loops or black holes as quicklyas possible by routing around the restarting router.A helpful neighbor considers a link down with the restarting router to be atopology change, regardless of the strict LSA checking configuration.nsf restart-intervalUse the nsf restart-interval command to configure the length of the graceperiod on the restarting router. Use the “no” form of this command to revertthe grace period to its default.Syntaxnsf [ietf ] restart-intervalsecondsno nsf [ietf] restart-interval• 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.•seconds — The number of seconds that the restarting router asks itsneighbors to wait before exiting helper mode. The restarting routerincludes the restart interval in its grace LSAs (range 1–1800 seconds).Default ConfigurationThe default restart interval is 120 seconds.Command ModeRouter OSPFUser GuidelinesThe grace period must be set long enough to allow the restarting router toreestablish all of its adjacencies and complete a full database exchange witheach of those neighbors.Exampleconsole(config-router)#nsf restart-interval 180
