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Figure 239 DHCP relay agent work process
As shown in Figure 239, the DHCP relay agent works as follows:
1. After receiving a DHCP-DISCOVER or DHCP-REQUEST broadcast message from a DHCP client,
the DHCP relay agent fills the giaddr field of the message with its IP address and forwards the
message to the designated DHCP server in unicast mode.
2. Based on the giaddr field, the DHCP server returns an IP address and other configuration
parameters to the relay agent, which conveys them to the client.
DHCP relay agent configuration task list
Complete the following tasks to configure the DHCP relay agent:
Task Remarks
Enabling DHCP and configuring
advanced parameters for the DHCP
relay agent
Required
Enable DHCP globally and configure advanced DHCP parameters.
By default, global DHCP is disabled.
Creating a DHCP server group
Required
To improve reliability, you can specify several DHCP servers as a
group on the DHCP relay agent and correlate a relay agent interface
with the server group. When the interface receives requesting
messages from clients, the relay agent will forward them to all the
DHCP servers of the group.
Enabling the DHCP relay agent on an
interface
Required
Enable the DHCP relay agent on an interface, and correlate the
interface with a DHCP server group.
With DHCP enabled, interfaces work in the DHCP server mode by
default.
IMPORTANT:
ï‚· You can enable either the DHCP server or the DHCP relay agent on
an interface. The latest configuration takes effect.
ï‚· The DHCP relay agent works on interfaces with IP addresses
manually configured only.
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