I am trying to get an external extension to register on 3CX, I have my router configured with DMZ to 192.168.100.10 (which is the 3CX system) and my firewall disabled (to get it working). Both the external Extension and Bind to Media server boxes are selected however I can not get any external phone to register. I have set the phones to go direct to my IP, I have tried both the 3CX phone and a Snom 190. I have 8 IP's configured through a Draytek Vigor 2800 but I can not get it to work any way I try it. Does anyone have any Ideas.