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.
Maybe look into a lockable network cabinet that you could put the DVR in. This would add a layer of physical security instead of diving into network security. For added security, run the network cable in conduit to prevent someone from cutting the cable outside the cabinet.