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New Member

Loopback commands for testing

I'm in the process of trying to troubleshoot the massive errors I'm receiving on one end of 3 T1s. After verifying line codes, framing and clocking with AT&T, I want to test the line with them. The problem is that they've never been able to see my equipment when they loop me. Is there a loopback command that I need to turn on to allow this? I need to turn it on for a VWIC-2MFT-T1 and WIC1-DSU. Thanks.

  • Other Network Infrastructure Subjects
16 REPLIES

Re: Loopback commands for testing

New Member

Re: Loopback commands for testing

I've read this page but I'm still not completeley clear:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fdial_c/fnsprt4/dcdchant.htm#1002839

My question is it "loopback local" that needs to be used to allow my service provider to test up to the router. If it is, is the router usable in this mode? I realize intrusive testing brings the line down but once they're done the line comes back up. If the line is in this mode, will this T1 have to wait for me to do a "no loopback local" to bring it up? Thanx.

Silver

Re: Loopback commands for testing

you may want to turn on service-module t1 fdl both on the serial interface . This allows the Lec to loop the card

New Member

Re: Loopback commands for testing

It sounds liek you have a Layer 1 issue. Do you have an extended DEMARC? Can ATT loop the SmartJack? If so, place a HARD loop at the end of your extended DEMARC (buy or make one). Once you have the hard loop at teh far end of the extension, have ATT test the circuit again. If they can see the loop, and your are certain your CSU is good, ask ATT to conduct a "STRESS TEST" for your T1 and request it for at least 60 minutes. Remember this is an intrussive test.

New Member

Re: Loopback commands for testing

Ok, I got AT&T to loop me up and when they did, I saw no errors:

Data in Interval 1:

0 Line Code Violations, 0 Path Code Violations

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

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

As soon as he let go of the line, the errors came back. I 'm not sure what this means. the other end of the T1 shows no errors either. Just the Calif location:

Data in current interval (755 seconds elapsed):

7287 Line Code Violations, 15185 Path Code Violations

221 Slip Secs, 0 Fr Loss Secs, 221 Line Err Secs, 2 Degraded Mins

143 Errored Secs, 143 Bursty Err Secs, 78 Severely Err Secs, 0 Unavail Secs

Gold

Re: Loopback commands for testing

how far in did the loop go ? If they went to their dmarc, then you may have cable issues between the demarc and your hardware

New Member
Silver

Re: Loopback commands for testing

slips & aborts are usually clocking issues , check with the service provider to find out who provides clock, if the provide clock make sure your service module is set to rx clock from the line . If they do not provide clock (this is generally the case in a point to point ) one side of your circuit needs to be set for internal clock and the other side needs to be set for line .

New Member

Re: Loopback commands for testing

Agreed. The Vegas side is set to internal while the Los Angeles is set to line. When AT&T looped me up, there were no errors but when they let it go they came back. Almost seems that I'm not able to clock off of Vegas...

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