OSPF Commands 1141Command ModeRouter OSPF Configuration modeUser GuidelinesThe grace LSA announcing the graceful restart includes a restart reason.Reasons 1 (software restart) and 2 (software reload/upgrade) are consideredplanned restarts. Reasons 0 (unknown) and 3 (switch to redundant controlprocessor) are considered unplanned restarts.nsf ietf helper disable is functionally equivalent to no nsf helper and issupported solely for IS CLI compatibility.nsf helper strict-lsa-checkingUse the nsf-helper strict-lsa-checking command to require that an OSPFhelpful neighbor exit helper mode whenever a topology change occurs. Usethe “no” form of this command to allow OSPF to continue as a helpfulneighbor in spite of topology changes.Syntaxnsf [ietf ] helper strict-lsa-checkingno nsf [ietf ] helper strict-lsa-checking• 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.Default ConfigurationA helpful neighbor exits helper mode when a topology change occurs.Command ModeRouter OSPF Configuration modeUser GuidelinesThe restarting router is unable to react to topology changes. In particular, therestarting router will not immediately update its forwarding table; therefore, atopology change may introduce forwarding loops or black holes that persist
