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Configuring DHCP relay agent
Overview
The DHCP relay agent enables clients to get IP addresses from a DHCP server on another subnet. This
feature avoids deploying a DHCP server for each subnet to centralize management and reduce
investment. Figure 287 sho
ws a typical application of the DHCP relay agent.
Figure 287 DHCP relay agent application
Operation
No matter whether a relay agent exists or not, the DHCP server and client interact with each other in the
same way (see "DHCP overview")
. For more information about DHCP packet exchange, see "Dynamic
IP address allocation process."
The following describes the forwarding process on the DHCP relay agent:
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 in a response.
3. The relay agent conveys the response to the client.
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