3Com Switch 8800 Advanced Software V5 Configuration Guide

DHCP OVERVIEW

Introduction to DHCP The fast expansion and growing complexity of networks result in scarce IP

addresses assignable to hosts. Meanwhile, with the wide application of the

wireless network, the frequent movement of laptops across the network requires

that the IP addresses be changed accordingly. Therefore, related configurations on

hosts become more complex. Dynamic host configuration protocol (DHCP) was

introduced to ease network configuration by providing a framework for passing

configuration information to hosts on a TCP/IP network.

DHCP is built on a client-server model, in which the client sends a configuration

request and then the server returns a reply to send configuration parameters such

as an IP address to the client.

A typical DHCP application, as shown in Figure 213, includes a DHCP server and

multiple clients (PCs and laptops).

Figure 213 A typical DHCP application

DHCP Address

Allocation

Allocation Mechanisms DHCP supports three mechanisms for IP address allocation.

■ Manual allocation: The network administrator assigns an IP address to a client

like a WWW server, and DHCP conveys the assigned address to the client.

■ Automatic allocation: DHCP assigns a permanent IP address to a client.

■ Dynamic allocation: DHCP assigns an IP address to a client for a limited period

of time, which is called a lease. Most clients obtain their addresses in this way.

DHCP client DHCP client

DHCP server