The Frontier techs came out and replaced our Spectrum cable internet with their Fiber.  They installed the ONT in the garage, and used the coax with a MOCA connection to the Deco M9.  It would not connect to the internet, although it was getting a valid IP address from the ONT.  We swapped the Deco for their provided Eero 6 Pro, and that worked just fine.  Went back to the Deco with the same NO INTERNET.  

So, we had to leave the Eero in place, connected to the ONT via MOCA, and then plug the Deco into the Eero.   I would prefer to just use the Deco alone, and don't want double NAT and another device using electricity. 

I have tried cloning the MAC address of each port of the Eero into the Deco, which didn't work.  I tried turning on the IGMP and WAN Unicast, both of which didn't seem to help.

The Eero is set to WAN port DHCP, and the Deco is set to Dynamic, so both the same.  I cannot find anything else to change.  I have rebooted the ONT and connected the Deco in place of the Eero and it gets the IP adress, but says NO INTERNET.

Hopefully someone can help!

If I cannot get this working, I will just have to buy more Eero nodes and eliminate the Deco.  

But, the Deco is faster and has been working fine for the last year or two.