DELL 8132 ユーザーズマニュアル

OSPF Commands

Use this command to enable OSPF graceful restart. Use the no form of this 

command to disable graceful restart.

nsf [ietf] [planned-only]
no nsf [ietf]
ietf — This keyword is used to distinguish the IETF standard 

implementation of graceful restart from other implementations. Since the 

IETF implementation is the only one supported, this keyword is optional.
planned-only — This 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).

Graceful restart is disabled by default

Router OSPF Configuration mode

Graceful restart works in concert with nonstop forwarding to enable the 

hardware to continue forwarding IPv4 packets using OSPFv2 routes while a 

backup unit takes over management unit responsibility. When OSPF 

executes a graceful restart, it informs its neighbors that the OSPF control 

plane is restarting, but that it will be back shortly. Helpful neighbors continue 

to advertise to the rest of the network that they have full adjacencies with the 

restarting router, avoiding announcement of a topology change and 

everything that goes with that (i.e., flooding of LSAs, SPF runs). Helpful 

neighbors continue to forward packets through the restarting router. The 

restarting router relearns the network topology from its helpful neighbors. 
This implementation of graceful restart restarting router behavior is only 

useful with a router stack. Graceful restart does not work on a standalone, 

single-unit router.

2CSPC4.X8100-SWUM102.book  Page 1244  Friday, March 15, 2013  8:56 AM