Orbi 772 backhaul through MoCa

Sorry, you cant interconnect what makes up your WAN and your LAN on the same network - mess is predictable...

To operate WAN (internet feed) and LAN (home network) traffic separately across your coaxial lines, your primary concern is preventing data loopbacks and protecting your network's security/performance.

Because WAN and LAN traffic must remain rigidly isolated to allow your router to do its job, how you approach this configuration depends entirely on your home's physical wiring.

Scenario A: You Have Separate Coaxial Runs (Highly Recommended - not what oyu want, tough...)

If you have access to your central junction box where all room coaxial lines meet, you should opt for physical isolation. This provides the best stability and guarantees maximum performance.

1. Isolate the Coax Paths: Inside your utility panel, disconnect the two rooms being used for the WAN link from the rest of the house. Use a standalone 2-way MoCA-compatible splitter (or a simple barrel connector if it's a direct room-to-room run) to connect only those two points.
2. Connect the Remaining Rooms: Connect all the remaining rooms designated for your home network to a separate multi-way splitter.
3. The Configuration: Keep all four goCoax MA2500D adapters at their factory-default settings. Since the signals cannot physically cross paths, pair one will securely handle your raw internet feed (WAN) and pair two will handle your home internet distribution (LAN).

Scenario B: Everything Must Share a Single Coaxial Network (Frequency Splitting)

If all your coaxial jacks must remain wired to the exact same central splitter, you cannot simply rely on the default settings or MoCA privacy passwords. If you do, your router's WAN port and LAN port will accidentally be bridged together over the MoCA mesh, crashing your network.

To resolve this on a shared cable, you must configure the pairs to operate on completely different frequency channels via the goCoax web interface:

1. Access the Adapter Settings: Unplug your adapters from the coax network. Connect a computer via Ethernet directly to one adapter, change your computer's static IP address to 192.168.254.10, and navigate to http://192.168.254.254 in your browser.
2. Configure Pair 1 (WAN): Log in (Default: admin / pps2020 or check the sticker on older units). Change the operational frequency mode to D-Band Low. Apply changes and restart. Repeat this for the second WAN adapter.
3. Configure Pair 2 (LAN): Log in to the remaining two adapters and change their frequency mode to D-Band High. Apply changes and restart.
4. Reconnect to Coax: Once reconfigured, you can plug all four back into the shared home coax. The WAN pair will only communicate on the lower frequencies, and the LAN pair will only communicate on the higher frequencies. 

Note: When splitting the spectrum this way, the maximum available bandwidth per pair drops from 2.5 Gbps to roughly 1 Gbps for WAN (1 channel) and 1.5–2 Gbps for LAN (3 channels), which is still plenty for most residential setups.

Stating that much: I don't have any current MoCa devices - key reason is that modern Cable TV network infastrcures here in old Europe don't have any spare bandwidth - plugging MoCa to a modern Cable TV network would cause another mess - for the other subscribers, and for you.