4000 Router Series Layer 3 - IP Services Configuration Guide

Because the DHCP relay agent and server are on different subnets, you need to configure static or

dynamic routing to make them reachable to each other.

DHCP server configuration is also required to guarantee the client-server communication through the

DHCP relay agent. For DHCP server configuration information, see "DHCP server configuration

xamples ."

Figure 22 Network diagram

Configuration procedure

# Specify IP addresses for the interfaces. (Details not shown.)

# Enable DHCP.

<RouterA> system-view

[RouterA] dhcp enable

# Enable the DHCP relay agent on Ethernet 1/1.

[RouterA] interface ethernet 1/1

[RouterA-Ethernet1/1] dhcp select relay

# Specify the IP address of the DHCP server on the relay agent.

[RouterA-Ethernet1/1] dhcp relay server-address 10.1.1.1

After the preceding configuration is complete, DHCP clients can obtain IP addresses and other network

parameters from the DHCP server through the DHCP relay agent. You can use the display dhcp relay

statistics command to view the statistics of DHCP packets forwarded by the DHCP relay agent. If you

enable relay entry record on the DHCP relay agent with the dhcp relay client-information record

command, you can use the display dhcp relay client-information command to view relay entries.

Option 82 configuration example

Network requirements

As shown in Figure 22, the DHCP relay agent (Router A) replaces Option 82 in DHCP requests before

forwarding them to the DHCP server (Router B).

• The circuit ID sub-option is company001.

• The remote ID sub-option is device001.

To use Option 82, you must also enable the DHCP server to handle Option 82.

Router B

DHCP server

Router A

DHCP relay agent

DHCP client DHCP client

DHCP clientDHCP client

Eth1/2

10.1.1.2/24

Eth1/1

10.10.1.1/24

Eth1/1

10.1.1.1/24