large processing delay on cisco 2621XM

[dbadic]

Can anyone help me out with this strange case. I have very simple scenario with one hub router 2621XM and a couple of spokes 2610 XM and 1600. They are connected over p-t-p serial interfaces over frame relay. Let's take one p-t-p interface as example

hub ip 209.x.x.29/30

spoke ip 209.x.x.30/30

Ping from hub to spoke takes ~200 ms

Ping from spoke to hub takes ~160 ms

Now before we replaced old hub router (2610) with new one hub and spoke pings were the same ~160 ms. User machines connected to the ethernet segment of the hub router can ping spoke serial interface with results around ~165 ms (faster then from hub router

itself). Now all fast switching on all interfaces is disabled and I'm guessing that there is something wrong with either time stamps on hub router or that router really induces additional 40 ms of processing delay while process switching locally originated packets. Those 40 ms would be of course way to much for processing delay on any of routers.

Also I used c2600-js-mz.122-15.T9.bin and c2600-js-mz.122-28.bin on the hub router with no differences also I used same IOS on spoke router and pings are good.

So it must be some strange hardware issue or something elementary that I'm missing.

Any similar experiences or any suggestions?

Thanks in advance.

[lgijssel]

Tough one! Are you 100% certain that all spokes produce equal results? Jumping to conclusions will easily lead you in the dark. If you could post the configs, we have a look at them also.

Otherwise, my experience is that the best way to troubleshoot this type of issues is to exchange equipment. Bear in mind that to start ruling out possibilities, you will have to change something. Have you already exchanged the serial WICs?

Is it an option to temporarily exchange the hub router with a spoke?

If the problem stays at the hub location, it is not the 2620 hardware. It could still be a configuration issue.

If the problem moves with the router, you can be sure that it has something to do with that router.

Exchanging the 2620 hardware could be a next step then.

Regards,

Leo

[dbadic]

Yes, this problem is consistent across all 5 spokes -ping from the hub will add 30-40 ms to the result from spokes creating strange case of asymmetric round trip delay over frame relay network (not quite possible, right?). My first intention was to go after IOS but that proved to be dead end since a couple of spokes running same IOS and upgrading IOS to later version didn't do anything on the hub. Configuration on this new router was carried

over from old cisco 2610 together with old WICs and everything worked fine on old hub. This is more like annoyance right now (ping that ar not generate on the router itself are switched as fast as expected) but we intend to run VoIP shortly over this network and I don't like having nut case router in the middle of it.I'm still hoping that someone out there

had some similar case with non hardware cause before I request replacement from cisco.

[glen.grant]

I guess I have to ask why you have chosen to turn off fast switching to begin with ? Unless you are having a problem with the lan overunning the serial interfaces I would leave it on . Have never turned off fast switching unless I have to debug something . Process switching does slow down things considerably because every single packet hits the processor as opposed to having it looked up in the fast switching cache when fast switching is enabled . Will also cause increased CPU usage.