Reference Guide

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 39. Configuring a Relay Agent
To view the ip helper-address configuration for an interface, use the show ip interface
command from EXEC privilege mode.
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Dynamic Host Configuration Protocol (DHCP)