I am trying to link my Deco M4 Ac1200 base unit to a TP Link TL-R600VPN router...so far no luck - I have port two configured as 'wan' but the deco does not recognize the internet...cable modem connected to port 1 (wan by default) ...my LAN is connected on the last port on the router via a TP Link 24 port unmanaged switch. Everything on the switch works  fine...has internet etc. The DECO directly connected to the modem works fine too...so the ports are fine on the deco. The deco connected to any other router port goes out to lunch and stays there. Red light on the top and no connection. 

For now I am back on my default config which is the modem directly plugged into the deco and the switch plugged into port two of the deco. That config works fine although I am having issues with video playback (previously flawless). I can live with that for now. 

Not a happy camper - phone support for home was unable to help and directed me to business support. I spent over an hour on hold with them and I dont have that kind of time to be honest. 

Any help appreciated...if I can get this resolved then I'm nearly back to where I was before Comcast screwed up my original connection. 

On that score as an aside...I had an arris router/modem working flawlessly until comcast dropped signal strength to the point that the unit can no longer maintain a stable connection. The connection meets comcast specs for signal strength which is unfortunately BELOW the minimum strength of the modem...result...everyone pointing fingers at everyone else.