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Router to router PINGs slow over Ether yet no line errors

I have 2 routers back to back over ethernet. They both perform QOS and OSPF but not on these interfaces. The pings are erratic between them but no line errors or drop packets on these interfaces. What could be the problem?

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Hall of Fame Super Silver

Re: Router to router PINGs slow over Ether yet no line errors

Michael

I am not sure that there is a problem. In the IOS responding to ping must be preformed in the CPU (process switching) and is a very low priority task. If a ping arrives and the router CPU is not busy it will respond fairly quickly. But if a ping arrives and the router CPU has some other task (could be clearing and relearning the ARP cache, could be processing routing updates or calculating the SPF for OSPF, could be many other things) then the router waits to respond to the ping while it finishes the other task.

So the variability in ping response that you are seeing may be the result of whether the CPU is busy or not. The router CPU may not look very busy when you do show process cpu because it is measuring average busy over some period of time. But if you were to look at the CPU at the instant that the ping arrives it may have some small spike of processing some task which delays the ping response.

HTH

Rick

New Member

Re: Router to router PINGs slow over Ether yet no line errors

Thanks. I have also seen Request time out in the PING. Again with no apparent line interface errors, I'm wondering if high CPU and/or low memory in one of the routers could cause this.

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