D-Link DXS-5000-54S Emulator - Page 884

5000 Series Layer 2/3 Managed Data Center Switch CLI Reference Guide OSPFV3 Graceful Restart Commands The OSPFv3 protocol can be configured so that it participates in the checkpointing service, such that the protocol can execute a "graceful restart" if the management unit fails. In a graceful restart, the hardware will continue forwarding IPv6 packets by using OSPFv3 routes at the same time that a backup switch takes over management unit responsibility. A graceful restart utilizes the concept of "helpful neighbors". When a fully adjacent router receives a link state announcement (LSA) from the restarting management unit that indicates its intention to perform a graceful restart, the adjacent router enters helper mode. When in helper mode, a switch continues to advertise to the rest of the network that those other network members still have full adjacencies with the router that is restarting, thus avoiding the announcement of a topology change and the possibility of a flood of LSAs and shortest-path-first (SPF) runs (which determine OSPF routes). Helpful neighbors continue the forwarding of packets through the restarting router as it restarts. The restarting router then relearns the network topology from those helpful neighbors. Graceful restarts may be enabled either for planned starts, unplanned restarts, or both. The operator initiates a planned restart through the management command initiate failover. A failover may be intiated in order to take the management unit out of service (for example, in order to fix a partial hardware failure), to address faulty system behavior that cannot be corrected via less severe management actions, or for other reasons. An unplanned restart consists of an unexpected failover resulting from a fatal hardware failure of the management unit or from a software hang or crash on the management unit. 8-104 nsf (OSPFv3) Enables the OSPF graceful restart functionality on a given interface. The no command disables graceful restart for all restarts. nsf {ietf [helper] | helper [disable | planned-only | strict-lsa-checking] no nsf Parameters helper ietf disable planned-only strict-lsa-checking Default The default is Disabled. Command Mode Router OSPFv3 Config Configure grafeul restart helpful neighbor. (Optional) This keyword is accepted but not required. Disable helpful neighbor support. (Optional) This optional keyword indicates that OSPF should only perform a graceful restart when the restart is planned (i.e., when the restart is a result of the initiate failover command). Terminate graceful restart helper mode on topology change. 8-105 nsf helper (OSPFv3) 878