Tony, Only other thing I might be running into is maybe a network loop when just connecting from the modem to the router during boot up, maybe a good feature to add to the router firmware for these...

@Tony Not that I see off hand, I'm just trying to use the Link Aggregation from the SB8200 (pictured below) to connect to the router via WAN-Aggregation on the WAN port and Port 1 of the router: Here...

Evening! Just picked up a C5400X router and I have an Arris SB8200 cable modem (both latest firmware, configured correctly, internet is working). I enabled link aggregation on the cable modem...