T1 'loss of frame' problems

Unanswered Question
Aug 13th, 2007

I have a T1 line that has suddenly become unstable. It was repaired by the Telco last week after it went down but over the weekend it has gone up and down several times. I'm fairly new at Cisco and all I can find for troubleshooting is to do a 'sh service-module' which gives me the following:

Module type is T1/fractional

Hardware revision is 0.96, Software revision is 0.2,

Image checksum is 0x73D70058, Protocol revision is 0.1

Receiver has no alarms.

Framing is ESF, Line Code is B8ZS, Current clock source is line,

Fraction has 24 timeslots (64 Kbits/sec each), Net bandwidth is 1536 Kbits/sec.

Last module self-test (done at startup): Passed

Last clearing of alarm counters 3d17h

loss of signal : 0,

loss of frame : 12, last occurred 02:17:26

AIS alarm : 5, last occurred 02:17:26

Remote alarm : 5, last occurred 01:57:48

Module access errors : 0,

Total Data (last 96 15 minute intervals):

0 Line Code Violations, 526 Path Code Violations

1 Slip Secs, 1114 Fr Loss Secs, 0 Line Err Secs, 236 Degraded Mins

4 Errored Secs, 2 Bursty Err Secs, 2 Severely Err Secs, 1115 Unavail Secs

Data in current interval (397 seconds elapsed):

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

I cleared the counters last Friday after the telco stated the line was repaired so all the alarms generated are over the last three days. Any idea what the issue may be? The line provider has stated that they can hit both ends to the CSU and have run intrusive testing to no avail. I don't have access to the equipment on the other end as it is a vendor's Cisco equipment we are connected to but they have told me they do not have any problems on their end. I'm at a loss here and any suggestions on what the problem is or additional troubleshooting steps would be very much appreciated.

I have this problem too.
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Paolo Bevilacqua Mon, 08/13/2007 - 11:04

Hi,

there isn't much that you can do on your side, just check again cabling to demarc be on the safe side. These are the typical symptoms of a faulty circuit, also consider we're in the middle of the summer and a repeater box or other device in some forgotten place can overheat and it take time and will before the repairmen can locate the fault once for all.

Hope this helps, please rate post if it does!

qbakies11 Mon, 08/13/2007 - 11:20

Is there any other troubleshooting I can do on the router or is it unlikely that the router/WIC card is causing the issue? Is there any other kind of log files or debugging I can enable to help troubleshoot?

Paolo Bevilacqua Mon, 08/13/2007 - 11:39

As I said, there isn't anything else you can do.

You can replace the the router/WIC and then find that the problem has gone away, but you won't never know for sure what the reason was, because telco may have fixed something in the meanwhile, and they are usually unable or unwilling to pass true information about their faults to customers.

As an appreciation to those providing answers,please rate useful posts using the scrollbox below!

Paolo Bevilacqua Mon, 08/13/2007 - 13:59

One thing I wanted to add. The AIS alarm that the router received 5 times since last reload, is quite an indication that the equipment on the other side was disconnected, rather than a fault in the circuit. Yes it can be a false alarm due to the bouncing circuit, but I would check with the vendor you are connected to if they were doing something with the router.

Thanks for the rating and good luck!

qbakies11 Tue, 08/14/2007 - 06:24

I'm still testing this line with the provider and have a different problem. I have replaced the 1720 router/WIC card to take them out of the equation, and replaced them with a 2610 router/WIC card configured with the same IPs, encoding, framing, etc. The line came up fine and I was going to let it run through the night to see if it resolved the issue. Before I left for the evening I cleared the counters on the service-module so I could check it this morning.

When I came in I didn't see any errors listed in the service-module so thought it went well last night. The provider called me and told me that their monitor last night picked up loss of frame again, but I didn't get any alarms generated on the service-module.

Then the tech stated that he was going to loop all the way into my CSU on the new router to do testing. He did and the CSU loop light on the card came up but I still didn't see any errors. On the other router when the line was put into loop for testing it generated an alarm so I'm thinking that there may be a problem with this WIC config generating alarms.

I have done:

service-module t1 remote-alarm-enable

debug service-module

Neither seem to have allowed 'loss of signal' or 'loss of frame' alarms that I was seeing on the other router when the line was put in loop for testing.

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