Chapter 3 Dhcp Relay Agent Configuration; Configuring The Dhcp Relay Agent; Introduction To Dhcp Relay Agent - H3C S9500 Series Operation Manual

Operation Manual – DHCP
H3C S9500 Series Routing Switches

Chapter 3 DHCP Relay Agent Configuration

When configuring the DHCP relay agent, go to these sections for information you are
interested in:

Configuring the DHCP Relay Agent

DHCP Option 82 Configuration
3.1 Configuring the DHCP Relay Agent

3.1.1 Introduction to DHCP Relay Agent

DHCP adopts a client/server model, where DHCP clients send requests to the DHCP
server dynamically and the DHCP server in turn returns corresponding configuration
information according to the policies configured for it.
Early implementations of DHCP only work when the DHCP clients and DHCP server
are in the same subnet. That is, they cannot work across networks. So, to implement
dynamic host configuration, you must deploy at least one DHCP server in each subnet,
and this is obviously uneconomical.
DHCP relay agent is designed to resolve this problem. Through a DHCP relay agent,
DHCP clients in a LAN can communicate with DHCP servers in other subnets to
acquire IP addresses. This enables DHCP clients of multiple networks to share a
common DHCP server and thus enables you to save your cost and perform centralized
administration.
DHCP client
DHCP client
Figure 3-1 Network diagram for DHCP Relay
The dynamic host configuration procedure with the DHCP relay agent is as follows:
A DHCP client broadcasts a DHCP request packet in the local network when it
starts up and initializes the configuration.
Figure 3-1 illustrates a typical DHCP relay application.
DHCP client
DHCP relay
DHCP client
3-1
Chapter 3 DHCP Relay Agent Configuration
IP network
DHCP server