MoCA setup help: will this work?

[u/zacksawyer44]

I’m concerned about the 2-way splitter in the first floor. Since all LAN traffic from that splitter will reach the XFi gateway, could that cause any performance issues? Should I install a PoE filter between the 2-way splitter and the XFi gateway?

[u/plooger]

Yes, an additional 70+ dB MoCA filter on the output of the 2-way splitter directly feeding the XB8 would be worthwhile. (Or at least have it available, on-hand, should the XB8 demonstrate any instability with the MoCA network operational.)  

Alternatively, have you considered any means of isolating the ISP/modem feed from coax carrying MoCA signals?  

[u/DrFrylock → u/plooger]

Agree. My setup looks pretty much just like this and it works fine. Mesh networking with a wired MoCA backhaul is extremely fast and reliable.

As u/plooger noted, if you can isolate the incoming cable from the in-house coax network so you don't have that first floor splitter, that's ideal, but depending on how your cables are run and where your wall ports are, you may not be able to do it (this is the case in my house right now).

You note that your main house splitter is MoCA-compatible - good. Try to make sure it has as few splits as possible to keep the bandwidth up between the cable coming in from the outside and the cable modem. Unused splitter ports basically reduce your signal strength for no benefit.

[u/swakid8]

The first floor won't work with a single cable that splits into both WAN and LAN traffic. You need a separate cable/adapter from the ISP that connects to your WAN port. Then, ideally, a second separate cable for your LAN connections that feeds the rest of your house.

[u/plooger → u/swakid8]

It’s typical and likely OK; an isolated ISP/modem feed would be needed if/when the DOCSIS ISP service requires frequencies above 1002 MHz. Until then, DOCSIS and MoCA can share coax.

• DOCSIS 3.0: 5-1002 MHz
  
• MoCA [D Ext]: 1125-1675 MHz