OSPF: Graceful Shutdown

In some situations its necessary to take a router down with as little disruption as possible.  This can be accomplished using the graceful shutdown feature of OSPF.  This allows OSPF to update its neighbors that the router is going down, simply by using the shutdown command on the OSPF configuration.  The router will immediately perform the following functions when shutdown is configured:

  • Drops all OSPF neighborships
  • Flushes all LSA it originated (floods all LSAs with the age set to 3600 seconds)
  • Send out Hello packets to its neighbors with the DR/BDR fields set to 0.0.0.0 with an empty neighbor prompting the neighbors adjacency states to fall back to the init state
  • Stops sending and receiving OSPF packets

Graceful restart can also be configured per interface using the ip ospf shutdown command.  Which basically does the same functions as above but does it for any neighbors or OSPF functions off of that particular interface.

 

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