Chapter 1 Dhcp Overview; Dhcp Principles - H3C S9500 Series Operation Manual

Operation Manual – DHCP
H3C S9500 Series Routing Switches

1.1 DHCP Principles

The fast expansion and growing complexity of networks result in scarce IP addresses
assignable to hosts. Meanwhile, with the wide application of wireless networks, the
frequent movements of laptops across networks require that the IP addresses be
changed accordingly. Therefore, related configurations on hosts become more
complex. Dynamic Host Configuration Protocol (DHCP) was introduced to solve these
problems.
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 implementation comprises a DHCP server and multiple DHCP clients
(PCs or laptops).
DHCP client
DHCP client
Figure 1-1 Network diagram for DHCP
I. IP address assignment
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
special DHCP clients, such as a WWW server.

Chapter 1 DHCP Overview

Figure 1-1 illustrates a network that employs DHCP.
DHCP client
DHCP server
DHCP client
1-1
Chapter 1 DHCP Overview