Hanging up on 'DAHDI/2-1' loop


I am currently using a FXS on my Sangoma A200 to provide DAHDI channels and for now I have only one in use.

Earlier today we noticed that there was no dial tone on this phone line and I saw the following in my logs:

[2015-07-26 06:36:29] VERBOSE[21910][C-00005bbd] sig_analog.c: – Hanging up on ‘DAHDI/2-1’
[2015-07-26 06:36:29] VERBOSE[21910][C-00005bbd] chan_dahdi.c: – Hungup ‘DAHDI/2-1’
[2015-07-26 06:36:29] VERBOSE[21911][C-00005bbe] sig_analog.c: – Starting simple switch on ‘DAHDI/2-1’
[2015-07-26 06:36:31] VERBOSE[21911][C-00005bbe] sig_analog.c: – Hanging up on ‘DAHDI/2-1’
[2015-07-26 06:36:31] VERBOSE[21911][C-00005bbe] chan_dahdi.c: – Hungup ‘DAHDI/2-1’
[2015-07-26 06:36:31] VERBOSE[21912][C-00005bbf] sig_analog.c: – Starting simple switch on ‘DAHDI/2-1’
[2015-07-26 06:36:33] VERBOSE[21912][C-00005bbf] sig_analog.c: – Hanging up on ‘DAHDI/2-1’
[2015-07-26 06:36:33] VERBOSE[21912][C-00005bbf] chan_dahdi.c: – Hungup ‘DAHDI/2-1’
[2015-07-26 06:36:33] VERBOSE[21913][C-00005bc0] sig_analog.c: – Starting simple switch on ‘DAHDI/2-1’
[2015-07-26 06:36:34] VERBOSE[21913][C-00005bc0] sig_analog.c: – Hanging up on ‘DAHDI/2-1’
[2015-07-26 06:36:34] VERBOSE[21913][C-00005bc0] chan_dahdi.c: – Hungup ‘DAHDI/2-1’
[2015-07-26 06:36:35] VERBOSE[21914][C-00005bc1] sig_analog.c: – Starting simple switch on ‘DAHDI/2-1’
[2015-07-26 06:36:36] VERBOSE[21914][C-00005bc1] sig_analog.c: – Hanging up on ‘DAHDI/2-1’
[2015-07-26 06:36:36] VERBOSE[21914][C-00005bc1] chan_dahdi.c: – Hungup ‘DAHDI/2-1’
[2015-07-26 06:36:36] VERBOSE[21915][C-00005bc2] sig_analog.c: – Starting simple switch on ‘DAHDI/2-1’

This repeats over and over and over a very long period of time…

I have two questions:

  • What caused this? Is there any way to know?

  • Is it possible to set up an alarm to be warned when this happens?

Any ideas?

Thank you very much for your help!


Unplug your phone, if that doesn’t fix it suspect your FXS hardware.

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I resetted it and it fixed it but it’s the reason why it happened that eludes me…

The only thing I could think of is that another line was connected to it yesterday, maybe it unseated the card a little but I didn’t need to reseat the card today so I am not sure that’s the actual reason…

Thank you very much for your help!


Your hardware, perhaps a poor or unfiltered PSU or a bad cable to the card? (you did plug that in didn’t you?), the cards hardware?, who knows?, but for many years I have been using Sangoma hardware, it is robust and I only remember two failures, Their service system is excellent also.

Yes, I definitely plugged it in…

As for Sangoma hardware itself I had a noisy FXS and it took quite a while to figure that problem out…

Bah, we will see if this happens again… In the mean time I will check if there is a way to somehow get an alert when this happens…

Thank you!


Well, not directly but an admix of installing SNMP on yourserver and a simple (or complicated) monitoring system would be the way to go, probably more cost/time effective to just replace the failing hardware.

You could technically have fail2ban watch the logs for this and email you.

I would have a hard time blaming the hardware based on the description. In my experience hardware is usually black and white. It typically works or doesn’t. These random “when the moon is out of phase on the 3rd Thursday of September when following the Packers winning a super bowl it does __________.” usually is not hardware. I would bet there is something funky on the line. My test here is to typically rearange wires and see if the problem moves assuming it doesn’t happen on other lines.

Even when the “moon is out of phase” fail2ban won’t work, it all revolves around detecting "<host>" in a log file, <host> is a regex that matches ip addresses, dahdi is not “network aware”, it is a channel driver. One solution might be