Sangoma Talk + NAT + Dynamic IP

I’m having a hard time using Sangoma Talk on one of our systems.
I know it’s a NAT issue, but I can’t find a way to fix it.

  • The system is on the local network, behind a PFSense Firewall
  • The public IP address is dynamic
  • Ports are forwarded to the FreePBX (SIP, RTP, Sangoma Phone Desktop Client Service)
  • The Sangoma Phone Desktop application works, but only if I specify ICE Host Candidates
  • Using ICE Host Candidates is an issue because it works only with IP addresses and not domain names. Having a dynamic IP address will create problems with this.
  • The mobile app has no audio. When testing from another LAN over the internet, the packet capture shows that RTP traffic is sent back to the LAN address of the mobile phone and not it’s public IP.
  • I have no issues with other sofphones like Bria, Zoiper or GS Wave and external physical phones are also fine.

I have another system with a similar setup and a fixed public IP, configured exactly the same, and everything is fine.

Where should I look for clues ? I looked pretty much everywhere I could think of…

It’s pretty much the same issue as this post:

There could be issues on different places, but you may try with enabled Advanced Network Settings on the user, set the NAT Traversal to Auto and Address for Contact to External. Also adding a STUN server may help. will have to re-provision the mobile app again after those changes.

Thanks for the reply.

I found the issue and now I hate myself !

I’m used to configure clouded systems. The hostname of the PBX always resolves to the IP address of the system.
Because my local system does not have a fixed pulic IP, I created a CNAME for the hostname that points to a DynDNS setup on the network. So externally, the hostname resolves to the correct public IP via the DynDNS

Where it hurts: for my local system, the hostname resolves to, which is normal…
During all the tests and changes that I’ve made, I somehow temporarly configured the external address with the current dynamic external IP address of the Internet to test the other softphones, which worked. But I must have reverted this back to the hostname after this. That’s why Sangoma Connect didn’t work.

The final solution was to simply use the DynDNS as the external address. As simple as that.
I guess I couldn’t see clear with all the tests I’ve done. Beginner’s error !

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