Solved No Audio on Teams calls

[Awjvail]

Hi there, using 3CX 18.1 on Windows.

Teams calls are functioning properly, but I have no audio on either side.

All requisite ports are open in the documentation, and they test fine when checking port forwarding.

My 3CX is configured with 2 interfaces:

INT 1: SIP trunk interface
Cable runs directly from my 3CX server into an interface on my ISP's equipment that they have configured for the SIP trunks.
This is configured with a local 10.0.0.0/8 address that was provided by the ISP.
This interface is configured by my ISP to just have access to their SIP trunks.

INT 2: Local LAN interface
This cable connects into our standard switching infrastructure, providing access to the physical phones and ultimately goes out to the internet.
This is configured with another local 10.0.0.0/8 address, and ultimately is NAT'd out to the internet.
This is the interface that 3CX should be using to communicate with Teams

The problem seems to be that the 3CX Media Server is using interface 1 (the SIP trunk interface) to attempt to communicate with Teams. During a Teams calls I can see 3CXMediaServer.exe listening on ports 9004, 9005, 9006, 9007 etc. on the SIP Trunk interface instead of the internet-facing interface.

Note that if I go into Settings > Network > Public IP and select interface 2 from the dropdown for "Select Network Card Interface", I get no audio on regular calls either.

Help?

 

[Awjvail]

I should note that if I switch Settings > Network > Public IP to interface 2 in the dropdown I am able to get 1-way audio (3CX->Teams) on internal calls, but I lose any ability to make external calls from either Teams or a physical phone.

 

[NickD_3CX]

This sounds like a Routing issue more than a Teams issue.
When you have multiple NICs, you need to tell the OS where to route traffic.

First check here the "Multiple internet gateways" section:
https://www.3cx.com/blog/docs/network-configurations-supported-3cx-phone-system/

I don't know which SIP provider you are using, but I imagine the setup is something similar to this:
https://www.3cx.com/docs/cypriot-sip-trunk-cyta/#h.felrzf762ecc

Leave the "SIP Trunk NIC" without a Default Gateway and add static routes just for the Signalling and Media Server IPs of your provider to use the default GW of the Providers box for SIP Trunking.
Then on the "Internet NIC" put the default GW.

Then in the Network tab of 3CX, select the "Internet NIC"

Also, in the SIP Trunk settings, in the "Options" tab manually set the IP your SIP Trunk provider expects (Public or Private, not sure):


After doing this you should be OK.

 

[Awjvail]

That worked, thanks!