I am not sure how this will relate,.. but I am staring at our PBX and and this page. And then I see the different port numbers - It's interesting to see so many that are not 5060
No relation. this is NAT networking 101.
All of your devices connect to pbx.ntg.co:5060
But their local outbound ports cannot all be 5060. How would the router know which devices to translate it back to.
Yup,. I get that. - well anyway. moving right along...