DELL PC7024 User Manual

OSPFv3 Commands

Use the nsf-helper strict-lsa-checking command to require that an OSPF 

helpful neighbor exit helper mode whenever a topology change occurs.  Use 

the “no” form of this command to allow OSPF to continue as a helpful 

neighbor in spite of topology changes.

nsf [ietf ] helper strict-lsa-checking
no nsf [ietf ] helper strict-lsa-checking

• 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.

A helpful neighbor exits helper mode when a topology change occurs.

Router OSPFv3 Configuration mode

The restarting router is unable to react to topology changes. In particular, the 

restarting router will not immediately update its forwarding table; therefore, a 

topology change may introduce forwarding loops or black holes that persist 

until the graceful restart completes. By exiting the graceful restart on a 

topology change, a router tries to eliminate the loops or black holes as quickly 

as possible by routing around the restarting router. 
A helpful neighbor considers a link down with the restarting router to be a 

topology change, regardless of the strict LSA checking configuration.

Use the nsf restart-interval command to configure the length of the grace 

period on the restarting router.  Use the “no” form of this command to revert 

the grace period to its default.

2CSPC4.XCT-SWUM2XX1.book  Page 1208  Monday, October 3, 2011  11:05 AM