It’s an ethernet wire that’s going to be exiting my house and running to a camera in a publicly accessible space. An attacker could disconnect the camera, connect a laptop and access my network. How could I protect against that (other than a physical lock)? I basically want to lock down that cable to the point where nothing works on it unless it’s the intended camera. If this was wireless, I’d just use MAC filtering, but I don’t see an equivalent for wired connections.
Switch - look at a second hand Cisco 3560e or x. You could even go one of the C3560CG-8PC 8 port switches if you can’t go a full rack mount option.
Router / firewall you could use a second hand mikrotik 750 or 951