Cisco NCS 5500 Series

When you use this command, the OSPF process must be up for at least 90 seconds before OSPF attempts to
perform an NSF restart.
Note
Step 6 nsfflush-delay-timeseconds
Example:
RP/0/RP0/CPU0:router(config-ospf)#nsf flush-delay-time 1000
Sets the maximum time allowed for external route learning in seconds.
Step 7 nsflifetimeseconds
Example:
RP/0/RP0/CPU0:router(config-ospf)#nsf lifetime 90
Sets the maximum route lifetime of NSF following a restart in seconds.
Step 8 nsfietf
Example:
RP/0/RP0/CPU0:router(config-ospf)#nsf ietf
Enables ietf graceful restart.
Step 9 commit
OSPF Shortest Path First Throttling
OSPF SPF throttling makes it possible to configure SPF scheduling in millisecond intervals and to potentially
delay SPF calculations during network instability. SPF is scheduled to calculate the Shortest Path Tree (SPT)
when there is a change in topology. One SPF run may include multiple topology change events.
The interval at which the SPF calculations occur is chosen dynamically and based on the frequency of topology
changes in the network. The chosen interval is within the boundary of the user-specified value ranges. If
network topology is unstable, SPF throttling calculates SPF scheduling intervals to be longer until topology
becomes stable.
SPF calculations occur at the interval set by the timers throttle spf command. The wait interval indicates the
amount of time to wait until the next SPF calculation occurs. Each wait interval after that calculation is twice
as long as the previous interval until the interval reaches the maximum wait time specified.
The SPF timing can be better explained using an example. In this example, the start interval is set at
5 milliseconds (ms), initial wait interval at 1000 ms, and maximum wait time at 90,000 ms.
timers spf 5 1000 90000
Figure 2: SPF Calculation Intervals Set by the timers spf Command
This figure shows the intervals at which the SPF calculations occur as long as at least one topology change
event is received in a given wait interval.
Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.3.x
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Implementing OSPF
OSPF Shortest Path First Throttling