Let me describe the bizarre situation here in simple terms.
- I need to get an Ethernet connection from the network closet to the garage TV.
- My main router is an OpenWRT Linksys wrt32x which has 5 gigabit Ethernet ports (1 WAN, 4 LAN; although this can be reconfigured for 2 WANs if we want for whatever reason), a USB 2.0 port, and a USB 3.0/eSATA port, both of which I can do whatever USB shenanigans I want (I own a rare USB-A male to USB-A male data link cable, and I've heard of running PPP over serial? if that's at all relevant).
- There is a single data line (CATV over Coax) that runs directly from the closet to the garage. This coax line is marked "DIRECTV RJ-6 75 Ohm High-Performance 3.0 GHz," which is kind of weird because we've never used DIRECTV on this line notwithstanding.
- The CATV signal isn't that important so replacing it with a data-only line is A-OK (but my ISP runs both on the same wire so I assume it's possible to do that myself as well).
- I have a DOCSIS 3.0 cable modem/router combo, the Cisco DPC3825, that as of now is being used just as a 4-port gigabit Ethernet switch. It has 4 gigabit Ethernet, 1 coax, and 1 USB port. This one doesn't have OpenWRT support unfortunately.
- The most obvious solution, wireless, is not usable because it's what we already have-- it hasn't been working at all. Given how terrible the speeds on even 802.11ac with the device 15 yards away have been I think there's some sort of interference in the garage due to some electrical equipment, but I'm no expert. It could also be that the access point is shitty, but regardless I prefer static wired setups to wireless ones if possible.
- I want to run a DOCSIS signal on this coax wire, over which the LAN (Link layer Ethernet/PPP/etc bridge OR network layer IP tunnel are both good) connection will run, that can be modem'd by the DPC3825. Essentially I want to be both the "customer" (garage) and the "ISP" (closet) at the same time.
- The topology of the link I'd like to achieve is this:
|_______Accessible_________|_Inaccessible_|_____________________________Accessible____________________________| | | | | Router <--Ethernet--> [???] <--Coaxial-Line--> DOCSIS 3.1 Modem <--Ethernet--> Switch <--Ethernet--> Garage TV
Basically all I'm looking for is the
[???] listed above. I've spent a while trying to find documentation on using DOCSIS for a LAN but nothing's turned up. It's not typical to run what's typically used an ISP's protocol WAN-LAN connection as a LAN-LAN connection, but I've actually done this kind of thing before, only with DSL/PPPoE instead, and it worked despite being super weird (all I did then was use OpenWRT as a PPPoE server and attached an old DSL modem). I want to take advantage of the modem I already own-- yes, MoCA/G.hn could solve this problem easy, but devices for them're quite expensive. Is it practical to emulate the PPPoATMoDOCSIS that my ISP uses?
I've no preference as to whether it's a solution involving layer 2 (Ethernet/PPP/etc) over DOCSIS or layer 3 (IP) over DOCSIS: just as long as I can get to my local subnet from both ends, it'll work; and since I've not been able to find anything about a sort of system like this, I'll try to try out what I can just for future reference if nothing else.