Reference Guide

Dynamic Host Configuration Protocol (DHCP) | 341
Debugging DHCP server
DHCP Clear Commands
Configuring the System to be a Relay Agent
The following feature is available on the S5000 switch.
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 command
ip helper-address dhcp-address from INTERFACE mode, as shown in the
illustration below. Specify multiple DHCP servers by entering the
ip helper-address dhcp-address command
multiple times.
When
ip helper-address is configured, 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.
HCP Relay Device
Task Command Syntax Command Mode
Display debug information for DHCP server.
debug ip dhcp server [events | packets]
EXEC Privilege
Task Command Syntax Command Mode
Clear DHCP binding entries for the entire binding table.
clear ip dhcp binding
EXEC Privilege
Clear a DHCP binding entry for an individual IP address.
clear ip dhcp binding ip address
EXEC Privilege
Clear a DHCP address conflict.
clear ip dhcp conflict
EXEC Privilege
Clear DHCP server counters.
clear ip dhcp server statistics
EXEC Privilege
Note: DHCP Relay is not available on Layer 2 interfaces and VLANs.