T-1 random slowness CRC and Frame errors

Unanswered Question
Jun 12th, 2008

We have a branch office connected by a point-to-point T-1. The branch office router will accumulate CRC and Frame errors and various times during the day. It is at this time that users report issues from the site. I have had the SP test and of course they say the circuit it clean. Of course while testing is being done the issue is probably not happening. I have ran my own loopback test on the equipment with no errors. The T-1 controller gets line and path code violations. We have verified framing and linecode settings are good. The other end of the circuit (headquarters)is complete clean of any errors. Thanks in advance for advice.

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Paolo Bevilacqua Thu, 06/12/2008 - 03:18

Hi, what exact router model and interface card are you using ? "show diag" will tell you this.

Pravin Phadte Thu, 06/12/2008 - 03:43


can you provide the output of show controllers

need to know whats the count of erros you are facing for this output.

Pravin Phadte Thu, 06/12/2008 - 05:55

Ensure the framing format configured on the port matches the framing format of the line.Confurm the same with the telco.

Issue the cablelength long or cablelength short command in order to change the line build-out (LBO) setting.

Change the cable.

Follow all these to troubleshoot the problem.

Also shut/no shut the cotroller.



Paolo Bevilacqua Thu, 06/12/2008 - 06:05


network-clock-participate wic 0

network-clock-select 1 t1 0/0

But since I'm not sure of platform, may not be accepted.

patrickvanham Thu, 06/12/2008 - 06:37

I blieve a show controller when the problem is occurring would be more informative. At that point I'd expect the controller to be down as well, likely with an alarm. That alarm would tell you in which direction to look. Unfortunaltely the controller isn't really down much.

You could also set a loop (network line) on the erroring side and ask the SP to do a 24 hour measurement since the problem is intermittent.

If there was a clocking or framing issue I'd expect the T1 to show those symptoms more consistently, but many of the intervals are clean. This does look like an issue with the line, but since it occurs infrequently it's hard to diagnose, I think a 24 hour measurement with a loop on your end could provide the SP with necessary data to isolate and diagnose the problem

mbroberson1 Thu, 06/12/2008 - 06:59

So to provide the SP with a loop on my erroring side whay is the best way to do this?


Pravin Phadte Thu, 06/12/2008 - 07:25


When we ask for the SP to test the link. They have a auto test which would test the link till the SJ (Smartjack) If the test is good they are clean. (You can conside this as a loop test). Futher they try to loop the routers CSU. if they can. its clean. If they cant its the CSU problem. (Your Side).

I am still not sure about the test which has been conducted by the SP for this link.

You need to specify the SP to have a "Intrusive test" on the circiut. they will ask for the time frame may be 1 or 2 hrs. At this time the ckt will be completely down. They test the circuit with diffrent pattents.

Hope this helps.




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