After 7 years my Linksys PAP2T died. VOIPO sent me a replacement Grandstream HT702. On the same day the replacement arrived I swapped from a hardware firewall with 100 Mbit cards to a firewall running in a VM with 1000 Mbit cards. Since my Internet was working on every other device it did not dawn on me that the firewall was the cause of my problem (sort of).

When I would dial out from my VOIPO phone there would be a small click or pop in the audio before the first ring and that would be that for the audio. Complete silence. The person getting called would see the call and could pick up but there was no audio in either direction. The call could be terminated from either end.

Incoming calls worked perfectly. I thought this was strange but the device had just arrived and I thought maybe it still needed to negotiate the right something or another. Basically I had other things going on and I was going to come back to why I could not place calls but I could receive them.

Apparently the 'randomly' selected MAC address in the VM was registered to a company in my city. I was getting placed on their LAN behind their firewall. I was getting a 100.65.x.x address which is apparently reserved for carrier-grade NAT. It looks like the double NAT broke outgoing calls but incoming worked fine. I have no idea if anyone else will ever run into something like this but I changed my MAC address and I received a normal IP address from my ISP and everything works fine now. Yay!