My college used to do similar. If you did not register your MAC address, you would be DHCP assigned into a walled-garden IP block.
We found we could run an IP scanner on the authorized subnet (from a computer with a whitelisted MAC), and find the unused IPs, and just set those statically for 'visitors'.
We found we could run an IP scanner on the authorized subnet (from a computer with a whitelisted MAC), and find the unused IPs, and just set those statically for 'visitors'.
No need to register any more MAC addresses.