OSPF error log on MPLS interface

[rys]

                   Dear Friends,

I have noticed a log message of  "%OSPF-5-ADJCHG:............ Too many retransmissions "on of our core router connected another core router, which are served as the backbone between the datacentres.

These routers are running MPLS in these interfaces, and has an MTU size of 4470 on both the interfaces.

But I am not able to  ping to the other end IP with this size, the Max size I can ping is 1590.

So is this MTU causing the OSPF logs.....

Kindly share your suggestions and thoughts  and what all things i need to verify.

Thanks in advance.

Riyas

[Vivek Ruhil]

Hi

hmm.. the configs and the ping looks fine.. could you please tell me the platform and the IOS version used. Also, what exactly do you see in syslog when this problem occurs. And how much is your box loaded (CPU Util)

[rys]

its a Cisco7206-S harware running advipservicek9 image,

Interface getting input errors and logs showing ospf down often.

CPU is 6% only for last 5 Min time.

This link is one of the core link connecting 2 datacentres. From the provider end they not seeing any errors.

Is this ospf error "too many retransmissions'' causing the ospf down or

is this the problem of fibre patching ??

The router is running with this config for 3 years, So MTU mismatch might not be the reason for the ospf down and error logs, I assume...

KInldy share your experience.

Thanks

Riyas

[Vivek Ruhil]

Hi

Is this ospf error "too many retransmissions'' causing the ospf down

Yes that is the reason why we have the OSPF instability, but, the reason we see too many retransmission is probably because of the interface errors you mentioned.

You need to have your interface clean to avoid this message. If you are receiving too many CRC then please correct the interface, try changing the port, the cable, clean fiber etc..

[rys]

HI

we have sheduled again a test with the Provider and change the cables,

During testing no errors...

But we are still receiving link flapping logs in the router.

The Interface Gig in our router supports Jumbo frames, but the provider set the MTU size to 1560. Does it has any impact on causing the input errors ???

Thanks

[Vivek Ruhil]

Hi

The Interface supporting Jumbo frames and the provider setting lower MTU has no impact.

What did the provider say about these link flaps ?

[rys]

The provider not seeing any errors and they claimed the link is error free.

Even after a 4 hr testing we didnt see any errors.

But we are having incrementing input errors at a slower rate in the router interface at one side,

and having ospf nei down logs in the other end of the router.

Thanks

[Vivek Ruhil]

hmm.. then the only option left is probably the hardware.

Could you try changing the SFP, or use a different port on a different module.

And I would recommend to open a TAC case as this has lingered for long now.

[rys]

Already try with a new SFP Module, and new cables, Now need to try with a new port.

Will update the result once we done.

Thanks for your supports.