It is not necessary for the remote locations to have port forwards unless they are behind a device or software firewall that is specifically configured to block needed outgoing ports. Since port requests originate from the LAN outbound, most routers will allow.
Some ports are the same. 5060, 3478, 9000 - 9009, if I remember correctly.
My remote now works like a charm though there were some challenges along the way. In the end my router was the main cause and a minor change in 3CX was the only other thing. It did require a router replacement to an older model believe it or not, the newer one believed it had to protect me regardless of what I wanted :lol:
If it does not work my first suggestion would be try another router or place 3CX in DMZ just to test if a port issue.
