Have you tried using PCP to forward the port? I was under the (maybe-incorrect, and if so I would really like to learn) impression that most major CG-NAT setups supported it.
Nah, many carriers don’t support it. I’ve always had to resort to STUN
STUN also isn’t guaranteed if the router is strict. IPv6 removes a lot of these unknown and strange ways that IPv4 infrastructure can break things.
Yep, my point was just that STUN works far more frequently than explicit port forwarding protocols. Part of the reason (for better or worse) is that most major console networks (Xbox live, PSN, etc) will grade your connection poorly if STUN doesn’t work. Customers who otherwise don’t know about networking do complain to ISPs about this sort of thing.
PCP is not widely deployed in South East Asia at the very least. Relying on it is not feasible.
I suppose I can try that some time. I can find absolutely zero mentions of that for the ISP, just the option of buying a static IP.