40-4
the client to uniquely identify an address allocation
process) in the message, and then forward the message to the DHCP server.
fter receiving the message, the DHCP server returns a DHCP-ACK message to the client:
ACK message is unicast, the DHCP relay agent directly forwards the message to the
client without replacing the XID in the message.
e message to the client.
D
Info
ts to obtain configuration parameters
successfully, S4500 series Ethernet switches support the DHCP Inform message handling feature.
ith this feature enabled, an S4500 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
Con
the XID (Transaction ID, a random value selected by
A
z
If the DHCP-
z
If the DHCP-ACK message is broadcast, the DHCP relay agent delivers the message to the CPU
to replace the XID, and then forwards th
A HCP client can only handle a DHCP-ACK message which has the same XID as that in the DHCP
rm message sent by the client. Therefore, to ensure clien
W
disabled, the switch does not replace the XID.
figuring the DHCP Relay Agent
z
Helper fun
z
clie
cted to it
cannot dynamically obtain IP addresses through BOOTP.
If a switch belongs to an XRN fabric, you need to enable the UDP
configuring it as a DHCP relay agent.
ction on it before
If an S4500 Ethernet switch is configured with DHCP Relay Agent, the
nts conne
DHCP
re the DHCP relay agent:
Relay Agent Configuration Task List
Complete the following tasks to configu
ask
Rem
T
arks
Enabling DHCP
Required
Correlating a DHCP Server Group with a Relay Agent Interface
Required
Configuring DHCP Relay Agent S
ns
ecurity Functio
Optional
Configuring the DHCP Relay Agent to Support Option 82
Optional
Configuring DHCP Inform Message Handling Feature Used in XRN System
Optional
Enabling DHCP
Make sure to enable DHCP before you perform other DHCP relay-related configurations, since other
DHCP-related configurations cannot take effect with DHCP disabled.
