What Is DHCP?

DHCP is a protocol used to automatically assign TCP/IP configuration parameters to computers. DHCP is a standard described in RFC 1531. Other RFCs—1534, 1541, 2131, and 2132—address enhancements and specific vendor implementations of DHCP. A DHCP server can supply a DHCP client with a number of TCP/IP settings, such as an IP address, a subnet mask, and the address of a DNS server.

Because the DHCP server is assigning the IP addresses, only the DHCP server must be configured with static IP address information. The only networking parameter you need to configure on the client end is an option for the client to receive IP address information from a DHCP server. The rest of the TCP/IP configuration is transmitted from the server. If some aspect of the TCP/IP configuration changes on the network, the network administrator needs only to update the DHCP server, rather than updating each client manually.

Furthermore, each client receives a lease of finite duration for the address. If the client is no longer using the address when the lease expires, the address can be assigned to another client. The effect of DHCP’s leasing feature is that, typically, a network will not need as many IP addresses as it has clients.

DHCP is especially important in today’s environment, in which many employees carry notebook computers between offices of a large corporation. If a laptop computer is configured with a static IP address, it must be reconfigured each time the traveling employee plugs into a different network. If the computer is configured to receive an IP address through DHCP, the laptop automatically receives a complete TCP/IP configuration each time the user attaches to a network with a DHCP server.