Just got AT&T Fiber service using their BGW320-505 ONT/Gateway. Also have Spectrum cable internet. Trying to setup Dual WAN in failover mode. I have the BGW320 in passthrough mode, and in single WAN mode, that works fine plugged into 10GB #1 port on the 16000. As soon as I plug in the Spectrum cable modem to the WAN port on the router and set to DUAL WAN failover mode, it completely kills the Internet connection. Lights are normal on the router, but speeds are so slow as to be unusable. Also in dual WAN mode with both services plugged in, I cannot access the router UI via the IP from a wired computer. I can get to the router UI via a wireless connection though. It feels like I'm missing something trivial, but I'm stumped ATM.