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Community Member

OSPF Routes keep being refreshed every 50 Seconds!

Hi,

I have a LAN conisisting of 6500 Switches with SUP 720's running 12.2(18)SEX4, using OSPF throughout.

Though the network is stable and we do not see any connectivity issues, I have noticed that every 50 secs, the OSPF routes keep getting refreshed. I would not expect these routes to refresh every 50 secs unless possibly there was an OSPF timer inconsistancy.

I have attached a text file showing this.

Can anyone explain this behaviour and what might be the cause?

7 REPLIES
Purple

Re: OSPF Routes keep being refreshed every 50 Seconds!

Hi Paul,

Unfortunately, the file has not come through - could you pls try again ?

Paresh

Community Member

Re: OSPF Routes keep being refreshed every 50 Seconds!

Sorry, here is the attcahed file

Purple

Re: OSPF Routes keep being refreshed every 50 Seconds!

Hi Paul,

I think there is a reasonable explanation for this. The routes that you see getting refreshed are external routes. What protocol are you redistributing these routes from ? My guess is that the external OSPF routes are getting refresh every time you receive an update from this other protocol that is redistributed into OSPF. You will not find internal OSPF routes doing this.

Hope that helps - pls rate the post if it does.

Paresh

Community Member

Re: OSPF Routes keep being refreshed every 50 Seconds!

Thanks, but I only showed a sample of the full routing table. I can confirm that all OSPF routes, both internal and external show this same sympton.

Cisco Employee

Re: OSPF Routes keep being refreshed every 50 Seconds!

You can use the "show ip ospf statistics detail" command to find out what is causing the SPF to be ran.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Community Member

Re: OSPF Routes keep being refreshed every 50 Seconds!

result - I tracked down a rogue router as shown as generating numerous SPF's and found a flapping interface on it (bouncing every 50 secs!). Shut down the interface and hey bingo.

Thanks very much

Community Member

OSPF Routes keep being refreshed every 50 Seconds!

Hi guys,

I also have similar problem in Cat-6500, all my external route (redistribute static) always refresh after 10 - 60 sec.

But, I check there is no flapping on the router interface.

Any idea?

Thanks,

Rp

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