How DHCP Works

DHCP is based on a client/server model, as illustrated in Figure 4.1.


Figure 4.1 The Basic DHCP Model

The network administrator establishes one or more DHCP servers that maintain TCP/IP configuration information and provide address configuration to DHCP-enabled clients in the form of a lease offer. The DHCP server stores the configuration information in a database, which includes:

  • Valid TCP/IP configuration parameters for all clients on the network.

  • Valid IP addresses, maintained in a pool for assignment to clients, as well as reserved addresses for manual assignment.

  • Duration of the lease offered by the server—the length of time for which the IP address can be used before a lease renewal is required.

A DHCP-enabled client, upon acceptance of a lease offer, receives:

  • A valid IP address for the network it is joining.

  • Additional TCP/IP configuration parameters, referred to as DHCP options.