Sometimes VoIP (Voice over IP) phones do not ring reliably when they are behind a router. With a port forward you can make sure that your VoIP phones ring every time someone is calling.
A port forward allows the VoIP system to connect to your phone from the outside, making much more reliable phone calls.
Port Forwarding Guides for VoIP
To use the port forwarding guides below, first, choose the device that you want to forward ports to. Then follow the steps in the port forwarding guide that shows you how to get your ports forwarded for VoIP. You may need to set up a DHCP reservation for your device. In the guide, you will be asked to choose your router from a list so that you get detailed instructions for forwarding ports in your specific router.