cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 
Highlighted
New Contributor

Atlas 550 Does Not Reestablish T1 Link After Loss

Here in California we have more rolling blackouts.

We have a simple system that routes an E&M line from one site to another via a T1 line.

When the power goes out and the phone company's batteries go dead in their remote terminal, the T1 goes down.

Then they power it up again and their T1 cards go all green but the Atlas 550s do not reestablish the actual audio path.


The error log shows many of the same type error, although I neglected to record it, it is something like LOS over and over again.

Power cycling both Atlases on both ends (one at a time) did not bring the link back up.

Both times, we have brought the link back up by logging in to the near end Atlas, setting that particular T1 port to Remote Loopback Enable and then immediately going back to Disable, and then the port seems to restart and everything works again.

I'm hoping there can be some setting that will allow the link to automatically reestablish instead.

0 Kudos
5 Replies
Highlighted
Valued Contributor
Valued Contributor

Re: Atlas 550 Does Not Reestablish T1 Link After Loss

It's possible that when the T1 comes back up, the ADTRAN is receiving a "remote loopback" signal in the "noise" while the circuit is coming up. I suggest you go under the modules, and the CONFIGURATION for the T1 module and set "LB Accept" to IGNORE. You may as well do this at both ends of the T1.

Hope this helps,

Patrick

Highlighted
New Contributor

Re: Atlas 550 Does Not Reestablish T1 Link After Loss

If this was the case, after failure and the line coming back up, can I find somewhere where it would tell me if it was stuck in remote loopback mode?

I have stepped pretty much through every menu when it was in the faulted condition trying to figure it out, and did not find anything that seemed out of the ordinary.  Despite being somewhat inexperienced (since these work so reliably otherwise) I would have noticed if something was in a loopback condition.

For reference, the thing that gets it to come back up:

MODULES (T1/PRI-1) > TEST > REMOTE LB

Set to AT&T INBAND LINE

Take back to normal

Line comes back online in a few seconds.

Highlighted
Valued Contributor
Valued Contributor

Re: Atlas 550 Does Not Reestablish T1 Link After Loss

Yes. If this is what you see in the menu:

MODULES (T1/PRI-1) > TEST > REMOTE LB

That indicates it is in "remote loopback" - meaning it received the loop-up command from a remote location.

You can also change it from REMOTE LB to NONE to resolve the issue, but configuring it to IGNORE the remote LB will prevent it from happening in the first place

Highlighted
New Contributor

Re: Atlas 550 Does Not Reestablish T1 Link After Loss

Rereading your response I want to be sure you understand me.

In the test menu, during the occurrence of the problem, REMOTE LB is set to NONE the whole time.

Getting in there and changing it to AT&T and then back to NONE kind of seems to restart the connection and make everything happy but the error log, which logs many of the same errors every 15 minutes or so, and the observed settings before making any changes, do not seem to reflect an idea that a remote LB has anything to do with the problem.

From memory, I believe the error that keeps repeating is "T1 [something] UAS Thrs Exceeded" 

Highlighted
Valued Contributor
Valued Contributor

Re: Atlas 550 Does Not Reestablish T1 Link After Loss

My mistake, then. If REMOTE LB shows NONE, then it is not in remote loopback.

You'd have to look at the ALARM status, because if the UAS Threshold is being exceeded, that is UnAvailable Seconds. So it sounds like either the T1 is in alarm, or it is receiving so many errors that it is unavailable.