Calls from outside my on-premises LAN do not have any audio

Hi guys,

I hope you can help me. I have set up FreePBX and am using Linphone to get started with calls and stuff like that. I am able to call from my linphone phone to desktop and hear everything perfectly when my phone is connected to my LAN wifi network, and when my desktop is connected to my LAN network.

Both phone and desktop are using Linphone softphone and connected through the FreePBX on premises server I have.

The problem is, when I take my phone off WiFi, therefore its connected to the internet via 4G, it does not work. The call connects to the desktop softphone, but there is no audio either way.

Also, very strangely, when my phone is on the 4G network external to the LAN, the phone cannot receive calls from the desktop. However, the phone calling desktop works! Just not the other way around. However, even phone calling desktop has no audio of course.

If you have any ideas I would be grateful, I have been stuck on this for a few days now.

Solved! Solution: add port forwarding for UDP ports 10000-20000 to my FreePBX server!

This all sounds like NAT rules not being set properly or not working. The not being able to receive may be the most difficult, as you won’t have the level of access needed to any NAT router in the mobile network, necessary to work round it. The only hope there might be to set up for very frequent re-registrations.

Have you set the public signalling and media addresses correctly on the PBX and have you set the local networks correctly? Have you enabled symmetric RTP? Is the phone able to use a stun server, or otherwise find its public address? Have you set up port forwarding on you router, for the FreePBX incoming RTP port range (almost certainly necessary if you are using encryption, or a non-standard port number. Does the router know how to extract the ports from the traffic and create temporary forwarding rules?

Rewrite contact might help with the calls to the phone.

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Solved! Solution: add port forwarding for UDP ports 10000-20000 to my FreePBX server!

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