Any computer can't have any IP, but the routing rules have nothing to do with physical location. Routers advertise to their neighbors the IP block(s) that they

Any computer can't have any IP, but the routing rules have nothing to do with physical location. Routers advertise to their neighbors the IP block(s) that they serve. As a super high level example, your ISP's core router would advertise to other ISP's routers that it serves 10.123.x.x IPs, so any IP address in that block gets sent to that router. Then within your ISP, the router in your area would advertise that it serves 10.123.45.x, so it receives packets for IPs in that more specific block from the core router. So your IP would have to be within the 10.123.45.x block, because that's what the router serving you is assigned.