I got 2 site and 2 pbx's on one side a s100 and the other side a s20 I cant get them to connected to each other. I have an extension set up on each one for remote register. I have the nat setup with the pubilic IP. I forwarded 5060 and 5061 to the PBX's I have rules set up in the firewall to accept traffic from the remote sites.
The only thing I can think of is the setup for the internet is a bit ODD the public IP address is delivered to a mikrotik radio which has its own internal ip range, there is a 1:1 nat on the MIkrotik to a Cisco router on site this cisco router is where I done my port forward to the PBX