I recently relocated all of my networking gear from distant side of the house into my ham shack. The key piece of hardware supplied by Frontier is an Arris model NVG468MQ gateway.
Background: A 25' length of cat 5e ethernet cable is inserted into the RJ45 jack on the 6400M. Opposite end of this cable is plugged into a LAN port on the Arris gateway, and the Arris DCHP server is ENABLED, and for best security, I have disabled UPNP on the Arris. Another (1 foot long) cat 5e cable extends from a LAN jack on the Arris gateway to my personal router, which is an Apple AirPort Extreme. The Airport should not have any impact on port forwarding: the Airport DHCP server is disabled, the Airport is set to bridge mode, and as noted, the radio connects directly to the Arris gateway, NOT to the Airport router. Eric (KE5DTO) posted very helpful remarks to another (closed) message thread on this board. In that posting, Eric remarked...
"you can look at the WAN IP through your router interface typically and compare that to what you see on www.whatismyip.com. If they don't match, you are probably double NAT'd."
I am confident that I am not in a double-NAT situation, because on my residential network the WAN IP that appears on the Arris gateway interface does match the IP address returned by whatismyip.com.
Here's a screenshot showing the way I have currently configured port forwarding on the Arris Gateway. Below, "host-36" is terminology automatically assigned by the Arris Gateway, and "host-36" = the known IP address of my 6400M radio. What additional steps/changes do I need to take to properly configure port forwarding on the Arris Gateway?