This is an example of typical installation. It is recommended that your site links are on a private network where latency it as a minimum and reliability is high. This is not a requirement and your backhaul to the remote sites can use the internet. The RTCM/Voter Board does not require port forwarding to connect back to the host. The only site that requires port forwarding is where your host computer is located. The only port for the RTCM/Voter Boards to function is the port they use to communicate which by default is port 667 using UDP. This port can be changed to whatever port you want or have available to use. This port is changed in the Voter.conf file and in the RTCM/Voter Boards as well. If you are using internet backhaul at one or more of your sites and you do have the ability to forward ports, the only port in my opinion you should forward is the Telnet port so that you can have remote access to the device to manage it. The fact that port forwarding is not required for the site to function also lends the devices to be being used with cellular modems. I do not recommend cellular backhaul with a site that has a simulcast transmitter due to cellular internet (depending on location and carrier) having highly variable latency and packet loss issues. For sites that are being used as voting receive only or non-simulcast repeater this can make an acceptable option for connectivity back to the host.