The DHCP protocol utilizes UDP ports 67 and 68, which are the same ports used by BOOTP.
DHCP Messages
The DHCP protocol consists of eight discrete message types:
DHCP Message
Description
DHCP Discover
UDP broadcast from DHCP client to locate available servers.
DHCP Offer
DHCP server to client in response to DHCP Discover with offer of configuration parameters.
DHCP Request
Client response to servers either; requesting offered parameters from one server and implicitly declining offers from all others, confirming correctness of previously allocated address after, e.g., system reboot, or extending the lease on a particular network address.
DHCP ACK
Server to client with configuration parameters, including committed network address.
DHCP NAK
Server to client indicating client's notion of network address is incorrect (e.g., client has moved to new subnet) or client's lease as expired
DHCP Decline
Error message from DHCP client to server indicating network address is already in use.
DHCP Release
Message from DHCP client to server releasing network address and canceling remaining lease.
DHCP Inform
Client asking DHCP server only for local configuration parameters because the client already has externally configured network address.
