What is DHCP?

DHCP is the Dynamic Host Configuration Protocol.

The DHCP protocol is utilized by some network nodes to automatically retrieve their network configurations from a centralized server.

The network configuration information provided by the DHCP server can include items such as:

DHCP clients are identified by their MAC addresses.

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.

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