I have 4 grandstream phones behind a UBNT AC ISP home router with the latest firmware.
Phone list is as follows:
A) 1 GXP2140 with firmware version 220.127.116.11 statically assigned IP address outside DHCP range.
B) 3 GXP2130 with firmware version 18.104.22.168 statically assigned IP address outside DHCP range.
There is an external PBX that all these devices are registering too and they all appear to register fine. Ring group rings all phones and but when answered dead air. Outgoing calls appear to work as expected and call quality is good. When calling from extension to extension calls will ring but when answered there is dead air. Tried using the changing NAT Transversal option to keep alive but with no luck. In fact that broke the ring group.
I am assuming that the firewall on the home router is breaking the connection. I don’t see how to port forward RTP ports to multiple endpoints on the router. In fact on this router it doesn’t appear to be able to do port ranges so you would have to port forward each port individually I believe.
I am not sure the best way to tackle this problem. I am assuming a STUN server or if there is some configuration on the phone that I am not aware of that I can utilize I would sure appreciate the help. Thank you for any and all suggestions.