Fundamentals
Figure 32: DHCP relay agent application
The DHCP server and client interact with each other in the same way with or without a relay agent (see "DHCP overview").
Figure 33: DHCP relay agent work process
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.
Based on the giaddr field, the DHCP server returns an IP address and other configuration parameters to the relay agent, and the relay agent conveys them to the client.