Dell PowerEdge M420 Reference Manual page 1174

Example
The following example sets the number of paths that OSPF can report for a
destination to 1.
console(config)#ipv6 router ospf
console(config-rtr)#maximum-paths 1
nsf
Use this command to enable OSPF graceful restart. Use the "no" form of this
command to disable graceful restart.
Syntax
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).
Default Configuration
Graceful restart is disabled by default
Command Mode
Router OSPFv3 Configuration mode
User Guidelines
Graceful restart works in concert with nonstop forwarding to enable the
hardware to continue forwarding IPv6 packets using OSPFv3 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
1174
OSPFv3 Commands