Cause 81 error - no inbound calls - phone line issue?

[Fox1977]

Hi there,
Just wondering if anyone can help me with an ongoing problem I don’t seem any nearer to solving.

We are experiencing a problem on our asterisk based phone system. Every Monday we come in and we are having a problem with inbound calls. After setting up our phone system to log to a syslog server it has become clear that the issue is with a Cause 81 error. This builds up and eventually the inbound calls stop working until we manually restart the phone system.

We have already had BT out numerous times to investigate a possible fault on the line with no success.

I’ve had a look online to see what a Cause No. 81 error is - invalid call reference value.

This cause indicates that the equipment sending this cause has received a message with a call reference which is not currently in use on the user-network interface.

Is this definitely down to a fault with BT? Can anyone suggest how I can approach this with BT as we haven’t had much luck as yet!

In order to test the fault I have disconnected the phone system from the lines with the issue. All being well the phone system should be back up and running on Monday.

Thanks in advance

 

[kodr]

What type of connection to you have? By line, do you mean analogue (POTS) lines, or ISDN (or something similar?)

 

[Fox1977]

We have ISDN2e lines from BT

 

[kodr]

Are the calls where you are getting the CC 81 inbound to you or outbound?

How I would approach it is to capture some call records and see if BT is sending you calls with a call reference number then rejecting that reference number later in the call flow.

If this is the case, you can use this to document the error with BT. If your PBX is sending out incorrect reference numbers, then you know the problem is on your side.

I don't know what distro/flavor of Asterisk you are using, but you should be able to turn on debugging to capture some call samples. Or use a protocol analyzer, if you have access to one.