SIP Trunk without port forwarding

[peteb]

I have just been setting up 3CX with a new SIP trunk from Spitfire.

While I was talking with one of their technical specialists, he told me to switch off all port forwarding on the router and disable the 3CX STUN client. This seemed crazy to me but I did it anyway and everything works fine!

Why does it work?

 

[A.burton]

Yep that'll work. The 3cx PBX initiates the connection and thus opens the port for you. You will be needing to open the port if you intend on having external/remote extensions.

 

[eagle2]

The correct answer is it depends on router. What brand / model is yours?

If your router is SIP ALG capable and this works correctly, you definetely don't need STUN, nor port forwarding (this scenario is not recommended by 3cx, as not all SIP ALG routers behave correctly, in some cases it's better to switch off SIP ALG).
Disabling port forwarding may cause problems with incoming calls after a while, unless 3cx sends reregister messages or keep-alives before expiry.

Regards