Telephone system problem!

Getting noticed

Telephone system problem!



We have implemented a new telephony system in our offices but the users are having problems when calling from one office to another office. The line just goes down at the same time on both ends. We use auto-vpn between the sites and we have full communication, nothing limited between the sites. Also the traffic to internet is straight out with nothing limited/blocking.


Has anyone else had this kind of problem before with auto-vpn?

2 Replies 2
Kind of a big deal
Kind of a big deal

@nikmagashi what license do you have on the MXs (enterprise, advanced or SD-WAN)?  What firmware are you running?  What phone system is it?


We are running 15.42, 15.43 and 16.11 on MXs with the enterprise license and use Cisco CUCM12 and with this and previous versions we don't have any telephony issues.  The earliest firmware we ran was 15.x, we never used the older releases.

Head in the Cloud

I don't think that this is a firewall problem. For me it sounds more like a phone system issue.

You might want to look into the SIP (I hope you are using SIP) messages. The "BYE" message should contain an Q.850 error code, which should give you a hint what the problem is


If the firewall would block the connection between both phones on the sited, then you would have an established call with no audio.

If the firewall would block the connection between the phones and the phone system, then the other phone would not even ring.


"The line just goes down at the same time on both ends" when does this exactly happen?

As soon as the other person is picking up the call?

If yes: Then it's probably a codec issue. e.g. Phone A can only use G711, Phone B only G722 -> call gets dropped

If you are using CUCM: Check also the Region/Location settings. Maybe the configured path is not possible here




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