3Com Switch 8800 Advanced Software V5 Configuration Guide

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DHCP RELAY AGENT CONFIGURATION
When configuring the DHCP relay agent, go to these sections for information you
are interested in:
■ “Introduction to DHCP Relay Agent” on page 735
■ “Configuring DHCP Relay Agent” on page 736
■ “Displaying and Maintaining DHCP Relay Agent Configuration” on page 741
■ “DHCP Relay Agent Configuration Example” on page 742
■ “Troubleshooting DHCP Relay Agent Configuration” on page 743
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The DHCP relay agent configuration is supported only on VLAN interfaces.
Introduction to DHCP
Relay Agent
Application
Environment
Since DHCP clients request IP addresses via broadcast messages, the DHCP server
and clients must be on the same subnet. Therefore, a DHCP server must be
available on each subnet. It is not practical.
DHCP relay agent solves the problem. Via a relay agent, DHCP clients
communicate with a DHCP server on another subnet to obtain configuration
parameters. Thus, DHCP clients on different subnets can contact the same DHCP
server for ease of centralized management and cost reduction.
Fundamentals Figure 216 shows a typical application of the DHCP relay agent.
Figure 216 DHCP relay agent application
DHCP clientDHCP client
IP network
DHCP server
DHCP relay
DHCP client DHCP client