I just received the XB6 today. I've set up port passthrough to my internal server running services on a variety of ports. In testing from my LAN workstations and WiFi devices I was unable to access any services via the domain name I've pointed to my external IP address.
However when I get my LAN device onto a VPN, or my mobile device off WiFi, my domain's services work perfectly fine.
I'm not able to figure out why - does anyone have any insight? If I tracert from a LAN device to my domain it is a single hop (and the endpoint is the modem IP). It almost feels like the modem isn't aware of the domain enough to pass through to the internal server if the request comes from the LAN side, but does if it comes from the WAN side.