When MyPBX is behind a NAT(firewall),you need to configure NAT
setting on MyPBX if you want to use a remote extension.
Please follow section 1 or 2 below depending on your network configuration.
1. If MyPBX is connected to a local network, you must set up port forwarding
on your router. Specifically, you must map port 5060 (default SIP port) and
port 10001-10200(default RTP port range) as UDP ports.