CANOGA PERKINS 9175 Command Reference - Manual (Page 631)

CanogaOS Command Reference
36-4
36.5 dhcp snooping information option
Use the dhcp snooping information option global configuration command on the switc to enable
DHCP option-82 data insertion. Use the no form of this command to disable DHCP option-82 data
insertion.
Command Syntax
dhcp snooping information option
no dhcp snooping information option
Default
DHCP option-82 data is not inserted.
Command Mode
Global configuration
Usage
You must globally enable DHCP snooping by using the dhcp snooping global configuration command
for any DHCP snooping configuration to take effect.
When the option-82 feature is enabled and a switch receives a DHCP request from a host, it adds the
option-82 information in the packet. The option-82 information contains the switch MAC address (the
remote ID suboption) and the port identifier, vlan-mod-port, from which the packet is received (circuit ID
suboption). The switch forwards the DHCP request that includes the option-82 field to the DHCP server.
When the DHCP server receives the packet, it can use the remote ID, the circuit ID, or both to assign IP
addresses and implement policies, such as restricting the number of IP addresses that can be assigned
to a single remote ID or a circuit ID. Then the DHCP server echoes the option-82 field in the DHCP reply.
The DHCP server unicasts the reply to the switch if the request was relayed to the server by the switch.
When the client and server are on the same subnet, the server broadcasts the reply. The switch inspects
the remote ID and possibly the circuit ID fields to verify that it originally inserted the option-82 data. The
switch removes the option-82 field and forwards the packet to the switch port that connects to the DHCP
host that sent the DHCP request.
Examples
This example shows how to enable DHCP option-82 data insertion:
Switch(config)# dhcp snooping information option
You can verify your settings by entering the show dhcp snooping config privileged EXEC command.
Related Commands
show dhcp snooping config
show dhcp snooping binding