Users Guide

Configure the System to be a Relay
Agent
DHCP clients and servers request and offer configuration information via broadcast DHCP messages. Routers
do not forward broadcasts, so if there are no DHCP servers on the subnet, the client does not receive a
response to its request and therefore cannot access the network.
You can configure an interface on the Dell Networking system to relay the DHCP messages to a specific
DHCP server using the ip helper-address dhcp-address command from INTERFACE mode, as shown
in the following illustration. Specify multiple DHCP servers by using the ip helper-address dhcp-
address command multiple times.
When you configure ip helper-address, the system listens for DHCP broadcast messages on port 67. The
system rewrites packets received from the client and forwards it via unicast; the system rewrites the
destination IP address and writes its own address as the relay device. Responses from the server are unicast
back to the relay agent on port 68 and the relay agent rewrites the destination address and forwards the
packet to the client subnet via broadcast.
Dynamic Host Configuration Protocol (DHCP) 360