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The grace LSA announcing the graceful restart includes the reason for the restart. Reasons 1
(software restart) and 2 (software reload/upgrade) are considered planned restarts. Reasons
0 (unknown) and 3 (switch to redundant control processor) are considered unplanned
restarts.
Default
OSPF acts as a helpful neighbor for both planned and unplanned restarts
Format
nsf helper [ planned-only ]
Mode
OSPFv3 Router Configuration mode
nsf ietf helper disable (OSPFv3)
This command is functionally equivalent to
compatibility.
Format
nsf ietf helper disable
Mode
OSPFv3 Router Configuration mode
no nsf helper (OSPFv3)
This command prevents OSPF from acting as a helpful neighbor.
Format
no nsf helper
Mode
OSPFv3 Router Configuration mode
nsf helper strict-lsa-checking (OSPFv3)
This command requires that an OSPF helpful neighbor exit helper mode when a topology
change occurs. 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 might introduce forwarding loops or black holes that persist until the graceful restart is
completed. By exiting graceful restart when a topology change occurs, a router tries to
eliminate the loops or black holes as quickly as possible by routing around the restarting
router.
The
parameter is used to distinguish the IETF standard implementation of graceful
ietf
restart from other implementations. Since the IETF implementation is not the only one
supported, this parameter is optional.
A helpful neighbor considers a link down with the restarting router to be a topology change,
regardless of the strict LSA checking configuration.
Default
A helpful neighbor exits helper mode when a topology change occurs.
Format
nsf [ietf] helper strict-lsa-checking
Mode
OSPFv3 Router Configuration mode
ProSafe Managed Switch
no nsf helper
IPv6 Commands
408
and is supported solely for IS-CLI
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