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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.
NOTE: DHCP Relay is not available on Layer 2 interfaces and VLANs.
Figure 34. Configuring a Relay Agent
To view the ip helper-address configuration for an interface, use the show ip interface command from EXEC
privilege mode.
Example of the show ip interface Command
Dell#show ip int tengig 1/3
TenGigabitEthernet 1/3 is up, line protocol is down
Internet address is 10.11.0.1/24
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Dynamic Host Configuration Protocol (DHCP)