High CPU due to OSPF

Unanswered Question
Nov 19th, 2008

Hi All,

We are running IGP as OSPF with multiple areas and observing high CPU only in couple of routers. These routers are configured ABR and the router CPU is constantly peaking due to OSPF. Though there are many other routers which are configured as ABR with less CPU only these routers are heavily loaded with CPU.

Is there any way to specifically troubleshoot the OSPF issue

How do we identify the cause of the issue due to what process in OSPF

thanks in advance

arun kumar

I have this problem too.
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rajivrajan1 Wed, 11/19/2008 - 03:51

hi arun,

In several cases , OSPF may not be the reason for CPU even it's in the top of sorted 5 min o/p of show proc.

If u r very sure that OSPF is causing this issue this page may help you


Please check the following

1.Ip accounting enabled

2. Ip cache flow enabled

3.Any unwanted service running

4.Any errors on Log

5.Any r u using any netflow / nbar - who is tha top chater ? what is the IP inpu load.

Answers may help u to figure out the issue.

Joseph W. Doherty Wed, 11/19/2008 - 04:29

If your high CPU is indeed caused by OSPF, often OSPF area topology calculation is the culprit caused by topology instability (e.g. link flapping).

Is yours a pure Cisco environment, or is there any brand "X"? Reason I ask, Cisco's implementation of OSPF has some "tweaks" that many other implementations don't offer which can impact OSPF.

At the moment, unable to offer any other suggestions, although Cisco's web site might offer some additional tech notes or white papers on the subject. Other posters might yet offer some additional suggestions.


Assuming you find and fix the cause of the issue, longer term, you might want to carefully review you OSPF topology. How OSPF is implemented has much control over how it responds to adverse situations. That's why you have general rules like no more then 3 areas per ABR or 50 routers per OSPF area, but such general rules aren't really "one size fits all".


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