Dhcp Overview; Dhcp Features Supported By The Ar150/200 - Huawei AR150 series Configuration Manual

Huawei AR150&200 Series Enterprise Routers
Configuration Guide - IP Service

6.1 DHCP Overview

DHCP dynamically assigns IP addresses to users and manages configuration information in a
centralized manner.
As the network expands and becomes complex, the number of hosts often exceeds the number
of available IP addresses. As portable computers and wireless networks are widely used, the
positions of computers often change, causing IP addresses of the computers to be changed
accordingly. As a result, network configurations become increasingly complex. DHCP is
developed to solve the preceding problems.
DHCP uses the client/server model. A client sends a configuration request to the server, and the
server replies with requested configurations, such as an IP address to the client. This allows
dynamic configuration for clients.
The early DHCP protocol is applicable only to the scenario where the DHCP clients and DHCP
server reside on the same subnet. This requires that each subnet be configured with a DHCP
server, wasting resources. The DHCP relay function is used to solve this problem.

6.2 DHCP Features Supported by the AR150/200

This section describes the DHCP features supported by the AR150/200
AR150/200 Functioning as a DHCP Server
The AR150/200 can be used as a DHCP server to assign IP addresses to online users. After a
DHCP client sends a packet to the server to apply for configuration parameters such as an IP
address, a subnet mask, and a default gateway, the server responds with a packet carrying the
requested configurations according to a certain policy. Both the request packet and the response
packet are encapsulated as UDP packets.
When the AR150/200 functions as a server, create an address pool on the AR150/200 to provide
IP addresses to DHCP clients. The address pool can be a global address pool or an interface
address pool.
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The AR150/200 allocates IP addresses to clients by using the global address pool or an interface
address pool.
AR150/200 Functioning as a DHCP Relay Agent
The AR150/200 supports the DHCP relay function. When the AR150/200 functions as a DHCP
relay agent, the client can communicate with a DHCP server on another network segment by
using the AR150/200, and obtain an IP address and other configuration parameters from the
global address pool of the DHCP server. In this manner, DHCP clients on multiple network
segments can share one DHCP server. This reduces costs and facilitates centralized management.
Issue 02 (2012-03-30)
After a DHCP server based on a global address pool is configured, all online users of the
server can obtain IP addresses from this address pool.
After a DHCP server based on an interface address pool is configured, only users that get
online from this specified interface can obtain IP addresses from this address pool.
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