I had a problem circuit like this once. The line would be good for a while
and would then go down for 8-10 hours sometimes longer and then come back
up. The line would go down, I would call the telco(AT&T), they would run
some loopback tests. Everything would be fine on the line. They would say
they saw abnormal station code coming from my end. I replaced everything
over a period of months. Even though I had already swapped the CSU/DSU I
called Kentrox and talked to them to see if they had any further insight. I
talked to great tech and he said, ask AT&T if they are doing a CSU loopback
or a DSU loopback. He said a CSU loopback is basically a polarity reversal
and doesn't test data integrity. Sure enough AT&T was only doing a CSU loop
and I ask them to do a DSU loop and they got nothing but trash. We was then
able to narrow the problem to a bad punch down at the smart jack. The punch
down was good enough to do the CSU polarity reversal, but would pass data
intermittently.
It turns out (at least to the AT&T guy I talked to) they only do CSU
loopbacks and hardly ever need to do a DSU loop. It is definitely something
to add to your bag of tricks.
Jim
CCNP, CCDA, MCSE, HP OpenView
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
John Neiberger
Sent: Tuesday, June 27, 2000 11:11 AM
To: [EMAIL PROTECTED]
Subject: Slightly OT: Telco Line Problems
We are having some odd line problems at one of our branches that none of us
have been able to figure out so I thought I'd throw this one out to the
group.
>From time to time, sometimes many weeks in between events, our csu/dsu
begins to report OOF and AIS (T1 yellow alarm) errors, but the line will
stay up for a while. Then, at some point, we'll get a T1 red alarm and the
circuit will die. We call USWest who then tests the line. According to
them, they've replaced just about everything between the CO and our
location, and the line tests clean. Friday it was bouncing every 30-60
seconds so we had them test it again. Since the test, it has been error
free but they claim not to have discovered any problems.
This is the endless cycle so far: the line dies, they test, they report no
problems, line mysteriously works fine after test for a several weeks, the
line has problems, the line dies, they test...etc.
My only remaining guesses are these two: bad csu/dsu that isn't bad all the
time, or intermittent problems at the location (we share it with a very
large supermarket.)
Any thoughts?
TIA,
John Neiberger, CCNA/CCDA
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