Advice needed: reaching an out of range eth only PC

My parents just got an FTTC connection, router included. It's all good with most devices but there's one desktop PC that is quite far from the router and has no WiFi onboard as well. There's no easy way to run an ethernet cable to the router. Moreover their house has two different power lines and router and desktop are on separate lines so no powerline extenders as well. Of course the main router is ISP managed and I can't just put OpenWrt on it.

I thought I could use one of my spare OpenWrt routers as a client cabled to the desktop. AFAIK it would be on a separate network but as long as this PC gets online I'm fine. Still I'm not sure it would work well as the signal is quite poor in that room.
Are there mixed solutions to consider? Client router + powerline? Ditch the main router wifi and buy a wifi card and some mesh repeaters for the whole house? Try some wireless extender solution?

What are my options?

Thanks for helping!

  • Coax/Ethernet bridge device (if your parent's network is wired as such)
  • Place ISP router downstream, use it
  • Place OpenWrt downstream, use it (you cannot bridge with Broadcom chips, but you can do a wireless WAN)
  • Yea, powerline I suppose

Doesn't have to be.

I would simply set WiFi to connect to the ISP's router as WWAN, and then your wired ports are LAN. See the note above if you want them on the same network in the future (i.e. bridged to the ISP's LAN).

The routed client configuration will work to get online.

Powerline can still work if both electrical drops are from the same transformer.

Their house consist of two joined apartments on different staircases; they have two different electric meters and brakers so I guess "plain" powerline would not work.
All I could do is to have both powerline adapters on the electric wiring where the PC is (not the router) and place the wifi one as close as possible to the router and the other one close to the PC. I don't even know it that could work as usually these powerline kits are meant to be use the other way (one adapter attached to the router with a cable and the wifi one extending the signal).

Their ISP use the old standard telephone cable and VDSL to reach the modem router (it's the last hop to the house only). They have to use their modem/router. I could use an OpenWrt device to mange the wifi only without dealing with more routing (double NAT?).

Maybe I think I didn't get it right... I read the connect client wiki page and I understood that in that case devices on the LAN ports of the OpenWrt client would have a different address than the one of the main router "due to technical limitations".

They would have separate addresses but the PC will still reach the Internet. The routed client wifi link takes one IP on the main router's LAN and makes it look like everything on the other side of the router (in this case, only one PC) is coming from the router itself.

This means that purely LAN operations like sharing files or printers are limited or won't work at all. Though newer printers using the "cloud" philosophy where everything goes to the Internet then comes back would still work.