So I'm setting up a test PBX for my company, we want to virtualize 3CX on Debian in our datacenter. I have the PBX set up and we have hard phones connected, but the Windows, iOS, and Android soft phones will not transmit audio. In our office I have a session border controller set up and the hard phones are connected via that. I ran tshark on the server and captured calls from when the soft phones were on WiFi, 4G, and a call from the Windows client on wifi to the iOS client on 4G. There don't appear to be RTP streams going through the tunnel.