Has anyone here dealt with VoIP issues when the ISP uses CGNAT? I’m running an ATA on a provider that uses CGNAT and I’m trying to figure out if others have seen similar behavior.
For anyone not familiar with CGNAT: instead of your router getting a true public IP, the ISP puts you behind a shared carrier‑grade NAT. So you end up with two IPs — an internal one assigned by the ISP and a single external IP shared among many customers. It generally works fine for most traffic, but it can complicate anything that relies on stable inbound connections, like VoIP.
My setup: Grandstream HT702 ATA behind an R7000 router. I’ve used this exact configuration on multiple ISPs without any issues. But on the one ISP that uses CGNAT, I occasionally get one‑way audio after about 10–15 minutes into a call. Everything starts fine, then suddenly I can hear the other side but they can’t hear me (or vice‑versa). Because this only happens on the CGNAT ISP, I’m pretty confident that’s the culprit.
I’m using TLS and SRTP, and I have keep‑alive enabled for both NAT and SIP. Has anyone found a configuration that plays nicely with CGNAT? Any tricks, settings, or workarounds that helped stabilize long calls?
I’d appreciate any suggestions or experiences.