2-2Figure 2-2 DHCP relay agent work processAs shown in Figure 2-2, 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 themessage to the designated DHCP server in unicast mode.2) Based on the giaddr field, the DHCP server returns an IP address and other configurationparameters to the relay agent, which conveys them to the client.DHCP Relay Agent Configuration Task ListComplete the following tasks to configure the DHCP relay agent:Task RemarksEnabling DHCP and ConfiguringAdvanced Parameters for theDHCP Relay AgentRequiredEnable DHCP globally and configure advanced DHCPparameters.By default, global DHCP is disabled.Creating a DHCP Server GroupRequiredTo improve reliability, you can specify several DHCP servers asa group on the DHCP relay agent and correlate a relay agentinterface with the server group. When the interface receivesrequesting messages from clients, the relay agent will forwardthem to all the DHCP servers of the group.Enabling the DHCP Relay Agenton an InterfaceRequiredEnable the DHCP relay agent on an interface, and correlate theinterface with a DHCP server group.With DHCP enabled, interfaces work in the DHCP server modeby default.z You can enable either the DHCP server or the DHCP relayagent on an interface. The latest configuration takes effect.z The DHCP relay agent works on interfaces with IPaddresses manually configured only.
