DHCP Overview

The Dynamic Host Configuration Protocol (DHCP) provides services for allocating and delivering IPv4 addresses and other IPv4 DHCP server options to Internet hosts. DHCP consists of two components: a protocol for delivering host-specific configuration parameters from a DHCP server to a host, and a mechanism for allocating network addresses to hosts. Optional functionality also provides services to complete high-availability, authenticated and QoS-dependent host configuration.

The DHCP protocol is based on a client-server model in which a designated DHCP server allocates network addresses and delivers configuration parameters to dynamically configured clients. Throughout the remainder of this section, the term “server” refers to a host providing initialization parameters through DHCP, and the term “client” refers to a host requesting initialization parameters from a DHCP server.

DHCP supports the following mechanisms for IP address allocation:

• Automatic — DHCP assigns an IP address to a client for a limited period of time (or until the client explicitly relinquishes the address).
• Manual — A client's IP address is assigned by the network administrator, and DHCP is used simply to convey the assigned address to the client.

The amount of time that a particular IP address is valid for a system is called a lease. The S- K- and 7100-Series devices maintain a lease database which contains information about each assigned IP address, the MAC address to which it is assigned, the lease expiration, and whether the address assignment is dynamic or static. The DHCP lease database is stored in flash memory.

Note

The S- K- and 7100-Series DHCP servers are not designed to work as the primary DHCP server in an enterprise environment with hundreds of clients that are constantly seeking IP address assignment or reassignment. A standalone DHCP server with a redundant backup server may be more suitable for this type of environment.