Configuring The Dhcp Relay Agent; Dhcp Relay Agent Configuration Task List - H3C S5600 Series Operation Manual

If an S5600 series switch belongs to a fabric, you need to enable UDP Helper and then DHCP relay
agent on it. Then, upon receiving a DHCP Inform message from a DHCP client, the switch will replace
the XID (Transaction ID, a random value selected by the client to uniquely identify an address allocation
process) in the message, and then forward the message to the DHCP server.
After receiving the message, the DHCP server returns a DHCP-ACK message to the client:
If the DHCP-ACK message is unicast, the DHCP relay agent directly forwards the message to the
client without replacing the XID in the message.
If the DHCP-ACK message is broadcast, the DHCP relay agent delivers the message to the CPU
to replace the XID, and then forwards the message to the client.
A DHCP client can only handle a DHCP-ACK message which has the same XID as that in the DHCP
Inform message sent by the client. Therefore, to ensure clients to obtain configuration parameters
successfully, S5600 series Ethernet switches support the DHCP Inform message handling feature. With
this feature enabled, an S5600 series switch that functions as a DHCP relay agent in a fabric can
replace the XID in DHCP Inform messages before forwarding them to the DHCP server. If this feature is
disabled, the switch does not replace the XID.

Configuring the DHCP Relay Agent

If a switch belongs to an IRF fabric, you need to enable the UDP Helper function on it before
configuring it as a DHCP relay agent.
If an S5600 Ethernet switch is configured with DHCP Relay Agent, the clients connected to it
cannot dynamically obtain IP addresses through BOOTP.

DHCP Relay Agent Configuration Task List

Complete the following tasks to configure the DHCP relay agent:
Enabling DHCP
Correlating a DHCP Server Group with a Relay Agent
Interface
Configuring DHCP Relay Agent Security Functions
Configuring the DHCP Relay Agent to Support Option
82
Configuring DHCP Inform Message Handling Feature
Used in IRF System
Task
Required
Required
Optional
Optional
Optional
3-4
Remarks