H3C s5820x series, Configuration Manual, Page: 38 / 209

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5
DHCP Overview
Introduction to DHCP
The fast expansion and growing complexity of networks have resulted in scarce IP addresses
assignable to hosts. Meanwhile, as many people need to take their laptops across networks, the IP
addresses need to be changed accordingly. Therefore, related configurations on hosts become more
complex. The Dynamic Host Configuration Protocol (DHCP) was introduced to solve these problems.
DHCP is built on a client-server model, in which a 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 5-1 , includes a DHCP server and multiple clients (PCs
and laptops).
Figure 5-1 A typical DHCP application
A DHCP client can get an IP address and other configuration parameters from a DHCP server on
another subnet via a DHCP relay agent.
DHCP Address Allocation
Allocation Mechanisms
DHCP supports three mechanisms for IP address allocation.
z
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.
z
Automatic allocation: DHCP assigns a permanent IP address to a client.