When a new machine is connected to urhnet the hub automatically detects a "intruder" and sends a trap to the management machine. The management machine looks up the card in its vendor database and assigns an IP address to that ethernet address.
The router will forward bootp requests to the management machine and that machine will assign an IP to that machine based on the inital detection and room location information. All packets are broadcast to all rooms but only the room with the correct hardware address will get the data payload. All other rooms will get alternating bits in the data payload.
If a machine tries to come up with an IP that is not normally assigned to that port the hub will send an "intrusion" trap to the management machine and the management machine will act accordingly.