Hello, I am definetly not an expert and looking for a little help. 

Goal: setup a Ethernet Backhaul between my 3 Deco X55's. 

I do not have Ethernet wired through my home so I looking to use the existing coax wiring for a moca network. 

I setup the connection as described below and the satelite deco's briefly show "Ethernet" as the source, but after a few minutes the main deco turns to red and the network crashes. I don't have a switch in my current setup, not sure if that could be the issue. My Moca adapters do show both LAN and moca as working. 

Setup: Incoming coax from wall to a splitter. Splitter goes to modem & moca adapter via coax. modem is linked to router via ethernet (Deco X55 router). Then the router goes to the moca adapter via ethernet. My ISP is Spectrum and I'm using a modem that they provide. Other rooms are coax from wall to adapter to Deco.

Thanks!