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Unstable OSPF


We've a network consisting of multiple areas. In one of the area, the spf algorithm is getting exceuted quite frequently. On an average spf is getting executed once in every 5 seconds. What could be the issue. There is no link failure.

In this area, lot of static routes have been injected and also being redistributed. Static routes have been injected to connect to another overlay network based satellite DAMA technology.

Is static route is the cause for spf execution or any other reason ?

Need some urgent help.


  • WAN Routing and Switching
Cisco Employee

Re: Unstable OSPF

If you execute the "show ip ospf stat detail", you should find out which router(s) is causing the SPF to be executed.

Hope this helps,

VIP Purple

Re: Unstable OSPF

Hello Sabut,

you might want to try and use the 'debug ip ospf events' command to find out what causes the SPF calculations. 5 seconds sounds like the router(s) in the area is constantly getting topology change information, because 5 seconds is the default SPF delay (which means that the SPF algorithm is run 5 seconds after the topology change has been received).

If you have no reachability problems, you could try and change the delay (and hold) timers, that will reduce the SPF calculations (of course you still need to find out what causes the instability, for which the above mentioned debug command is useful).

Use the command 'timers spf 60 120' under the routing protocol configuration to change the SPF delay and hold timers to 60 and 120 seconds, respectively.

Once you have the results of the debug (which should not take very long), can you post those ?



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