We recommend that you forward the following ports on your router or firewall:
Port 5060 TCP and UDP
Port 5004 UDP
Port 10000 UDP (sipgate Stun service - usually 3478/9)
Ports 16348-32768 UDP (RTP, RTCP multimedia streaming)
For IAX registrations and usage, please allow UDP port 4569 (the obsolete IAX1 protocol used port 5036). IAX2 uses ONLY one udp port for both control and data traffic.
We also recommend that you update your firwall white-listed IP addresses or allow rules to include the IP addresses held on the support article here