The ISP provided the Cisco EPC2425 router. It ain't listed on either for basic connection. Forwarding 113 & 6660-6669 made no difference.

Cannot change router either as their modem/routers can only be used on their network.

Reverse DNS is impossible. Any site trying to lookup my hostname will only find its IP!

I'm in an ongoing battle with them to admit their part in the problem as their previous router(non-Cisco) worked fine for IRC.