No Audio when on cellular connection, only wifi

[Chuck217]

I have an extension on my 3CX system that I am using a 3rd party app to access the phone. The reason I am doing this, I already have another extension on another system that I need to actively monitor so I can't be switching the accounts back and forth in the 3CX app. The problem is, I don't get audio at all when I place calls or receive calls, when I'm connected through T-Mobile's cellular network, only when I'm connected to some sort of wifi -- I have another system set up, FreePBX, that uses the same ports, 5060 etc, and I have no problems placing and receiving SIP calls through that system, only the 3CX system -- Any thoughts on how I can troubleshoot this? The only thing that popped in my head is that maybe my phone is getting an IPv6 address from T-Mobile and my 3CX isnt set up corretly for that?

 

[leejor]

You are asking, in a 3CX forum, for support of a 3rd party SIP App which you fail to identify? If the App works on Wifi, and I'm assuming that is not just Wifi on the same LAN as the 3CX server, then it is not a 3CX issue. What I would do, is ask a friend to borrow a SIM, from another network, and see if that works. It would confirm an issue with T-Mobile. It should be pretty straight forward to see if your phone is getting an IPV4, or 6 IP.

 

[Chuck217]

I've tried many apps, Zoiper, SipDroid, Voiper, the same thing, I can places or receive calls, with no audio, while on T-Mobile's network. 3CX itself is located on Vultr, but calls have audio and work, on any of those mentioned Apps, while connected to ANY Wifi, And I just found it interesting, that I can make another SIP connection, to a different server all together while on T-Mobile, and everything works, which makes me wonder where the problem actually is.. [email protected] works on T-Mobile, but [email protected] doesn't

 

[leejor]

It sounds (no pun intended) like you have narrowed down the issue to T-Mobile, as other Apps are having the same issue. The 3CX App is probably set to use the 3CX Tunnel, which is usually able to overcome many SIP network issues as there are no separate audio ports used. Perhaps T-Mobile is handing you a private IP.

 

[JohnS_3CX]

You are probably behind a carrier NAT and there is no path for the audio. The 3CX tunnel can usually bypass the NAT hence you should have audio.

You might also have to look at a capture and see what the 3rd party app sends in the SDP section as a contact address.

 

[leejor]

You might also consider contacting T-Mobile, in the hopes of being connected to someone with the technical knowledge, to understand what you are talking about. It's a bit of a long-shot, but if you don't ask....