Users Guide

following illustration. Specify multiple DHCP servers by using the ip helper-address command
multiple times.
When you configure the ip helper-address command, the system listens for DHCP broadcast
messages on port 67. The system rewrites packets received from the client and forwards them via unicast
to the DHCP servers; 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 67 and the relay agent
rewrites the destination address and forwards the packet to the client subnet via broadcast or unicast,
depending whether the client has set or cleared the BROADCAST flag in the DHCP Client PDUs.
NOTE: DHCP Relay is not available on Layer 2 interfaces and VLANs.
Figure 35. 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)