Dynamic Host Configuration Protocol (DHCP) allows for the automated distribution of IP addresses from a centralized server. DHCP follows a client-server model, with the following request-response pattern:
DHCP Discover is a broadcast transmission over UDP ports 68 (client side) and 67 (server side). DHCP Offer is unicast from the server to the client. DHCP Request is broadcast from the client, to any listening DHCP servers, letting all the servers know which one the client is accepting an address from. DHCP Acknowledgement is unicast back to the client, providing all needed information about the lease.
The DCHP message format is similar to the earlier Bootstrap Protocol (BOOTP). DCHP improves on BOOTP by allowing for dynamic, rather than static, IP address to client bindings. Nevertheless, a network scan discovering open ports 67 and 68 will report BOOTP as the running protocol, because DHCP provides essentially the same service using the same network bindings.
DHCPv6 has also been specified, allowing IPv6 hosts to acquire addresses from a server, rather than through the Stateless Address AutoConfiguration (SLAAC) process.