Extended Loopback Tests for T1/56K Lines

Unanswered Question
Jul 6th, 2007

I have read Extended Loopback Tests for T1/56K Lines Document ID: 5708,

i m having problem with customer router that have many errors and path code violation but telco had performed BERT test found no error on the line

Customer router was configured with Frame relay,

I would like to install other router to the line with basic configuration encap HDLC. Can i do extended ping test by send packet continuously for 24hrs? If can, how to do it?

If no error after the ping test, can i conclude the customer router faulty? Is this valid test in term of sh interface counter value although i config encap HDLC but customer router encap with frame relay?

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Paolo Bevilacqua Fri, 07/06/2007 - 06:36


No you can't config customer router for hdlc as it is connected to a frame switch and would not communicate. Actually there isn;t much you can do unfortunatley beside having a test unit placed inline with the router and run test again on the circuit.

How is the cabling from demark to module ? Are they using the right cabling / pairing to demarc ?

sukhoi33i Fri, 07/06/2007 - 06:52

i mean here to use other router not customer router & apply a loop at last point on telco line before connected to the frame switch

telco fiber mux--cisco balun---rj45---customer router E1 interface. No coxial cable customer internal wiring

Paolo Bevilacqua Fri, 07/06/2007 - 07:59

What router / interface is this with the problem? E1 ? Can you send show controllers e1 ?

Which pinout/paring for the rj45 cable between router and balun ?

sukhoi33i Fri, 07/06/2007 - 08:20

Thanks for your feedback.., really appreciated,

here is show controller E1. Latest sh controller E1 show almost 40000 path code violation which all error triggered

E1 0/0/0 is up.

Applique type is Channelized E1 - balanced

No alarms detected.

alarm-trigger is not set

Version info Firmware: 20050620, FPGA: 16, spm_count = 0

Framing is CRC4, Line Code is HDB3, Clock Source is Line.

CRC Threshold is 320. Reported from firmware is 320.

Data in current interval (74 seconds elapsed):

0 Line Code Violations, 33 Path Code Violations

0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins

0 Errored Secs, 0 Bursty Err Secs, 3 Severely Err Secs, 0 Unavail Secs

Paolo Bevilacqua Fri, 07/06/2007 - 08:28

Please send "show network-clock" and related config commands for network-clock-participate ans network-clock-select.

Wich IOS are you running? Is this a VWIC or VWIC2? There is newer firmware in latest IOS I believe.

Also important, please verify the rj45 cable to balun is NOT a standard ethernet cable. At very minimum, it must be crimped per t1/E1 cabling that is different than ethernet.

sukhoi33i Fri, 07/06/2007 - 08:41

I cannot login on frame relay switch or customer router.I just received the sh int,sh controller by email from my oversea ally, I m telco engineer , all the router manage remotely by my company oversea ally.

Thats why i m asking to do extended ping test using different router to prove no problem on the line even though its proven using telco BERT tester.

Thanks for the feedback

Paolo Bevilacqua Fri, 07/06/2007 - 08:56


the thing is that is the above commands are required in the router to make the circuit work clean of errors, and also the cable used is important as incorrect cabling can cause errors.

Once you have these two facts verified, you may think what would be the next troubleshooting step.

sukhoi33i Fri, 07/06/2007 - 09:10

Thanks for your info. It's quite difficult/impossible for me to get the command as all the configuration is a secret by the ally(giant company in the world).

What i can do now to follow your advised is to re-check the cable pinout.

else to argue with them there is really no problem on the line

Paolo Bevilacqua Fri, 07/06/2007 - 09:21

Here we are not talking about the complete configuration, but just two commands needed to make layer 1 work well. And the "show" command to verify that.

The cable as I said is very important as TE/E! must use ping 1-2 and 4-5 with twisted pairs, that is different from ethernet, unfortunately many installer don;t care and use any sapre ethernet patch and tis is wrong.

Good luck.


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