User's Manual

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Chapter 52 Configuring DHCP
52.1 Overview
Dynamic Host Configuration Protocol (DHCP) is used to provide some network configuration parameters for
the hosts on the Internet, which is described in details in RFC 2131. One of the major functions of DHCP is to
distribute IPs on an interface. DHCP supports the following three IP distribution mechanism:
Automatic distribution
The DHCP server automatically distributes a permanent IP address to a client.
Dynamic distribution
The DHCP server distributes an IP address for a client to use for a certain period of time or until the client does
not use it.
Manual distribution
The administrator of the DHCP server manually specifies an IP address and through the DHCP protocol sends
it to the client.
52.1.1 DHCP Application
DHCP can be applied at the following cases: You can distribute IP address, network segment and related
sources (such as relevant gateway) to an Ethernet interface by configuring the DHCP client.
When an SWITCH that can access DHCP connects multiple hosts, the SWITCH can obtain an IP address
from the DHCP server through the DHCP relay and then distribute the address to the hosts.
52.1.2 Advantages of DHCP
In current software version, the DHCP client or the DHCP client on the Ethernet interface is supported. DHCP
has the following strong points:
Fastening the settings;
Reducing configuration errors;
Controlling IP addresses of some device ports through the DHCP server
52.1.3 DHCP Terms
DHCP is based on the server/client mode. So the DHCP server and the DHCP client must exist at the same
time:
DHCP-Server
It is a device to distribute and recycle the DHCP-related sources such as IP addresses and lease time.
DHCP-Client
It is a device to obtain information from the DHCP server for devices of the local system to use, such as IP
address information.
In a word, there exists lease time during the process of dynamic DHCP distribution:
Lease time – it means the effective period of an IP, which starts from the distribution. After the lease time, the