Subnet routing via a macOS machine

I have three machines, let’s call them A (a 3d printer), B (a mac mini), and C (a mac laptop).

A, the 3D printer, cannot have tailscale installed on it. It’s connected via an ethernet cable to B, and has the local IP assigned to it by B. I can access it from that machine on that IP address just fine.

B and C both have tailscale installed, and can route to each other just fine. Both B and C have tailscale installed via the mac App Store.

I’ve reviewed Subnet routers and traffic relay nodes · Tailscale a couple of times, and ran the following on B: /Applications/ up --advertise-routes=, subsequently approving the subnet-routes prompt in the tailscale UI. is listed as a subnet route on the dashboard.

I can’t figure out what that’s actually done for me, though. If I attempt to ping from C, it just times out, presumably because C is looking for that IP over the local network, not over the vpn. I don’t have quite enough networking knowledge to get much further than this.