3com 8807 사용자 가이드

This is a world where networks are ever-growing in both size and complexity, and 
the network configuration is getting more and more complex. As is often the case, 
the number of hosts in a network exceeds that of the available IP addresses, and 
position changes of hosts (when users carry their laptops from here to there, or 
move to a wireless network) require reassigned new IP addresses. Dynamic host 
configuration protocol (DHCP) is designed to accommodate this context. DHCP 
adopts client/server model, where DHCP clients send requests to the DHCP server 
dynamically and the DHCP server in turn returns corresponding configuration 
information (such as IP addresses) according to the policies configured for it.

A typical DHCP implementation comprises a DHCP server and multiple DHCP 
clients (PCs or laptops). Figure 160 illustrates a network that employs DHCP.

Figure 160   Network diagram for DHCP

1 IP address assignment policy

Different types of clients have different requirements for IP addresses. Servers 
usually require long-term fixed IP addresses, some hosts may require automatically 
assigned long-term fixed IP addresses, and some hosts may only require 
dynamically assigned temporary IP addresses.

A DHCP server provides three policies to meet these requirements.

■

Manual IP address assignment. The administrator assigns fixed IP addresses to 
DHCP clients that are of special uses, such as a WWW server.