C
HAPTER
24
| General Security Measures
DHCP Snooping
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ip dhcp snooping
information option
This command enables the DHCP Option 82 information relay for the
switch. Use the no form to disable this function.
SYNTAX
[no] ip dhcp snooping information option
DEFAULT SETTING
Disabled
COMMAND MODE
Global Configuration
COMMAND USAGE
â—† DHCP provides a relay mechanism for sending information about the
switch and its DHCP clients to the DHCP server. Known as DHCP Option
82, it allows compatible DHCP servers to use the information when
assigning IP addresses, or to set other services or policies for clients.
â—† When the DHCP Snooping Information Option is enabled, the
requesting client (or an intermediate relay agent that has used the
information fields to describe itself) can be identified in the DHCP
request packets forwarded by the switch and in reply packets sent back
from the DHCP server by the switch port to which they are connected
rather than just their MAC address. DHCP client-server exchange
messages are then forwarded directly between the server and client
without having to flood them to the entire VLAN.
â—† DHCP snooping must be enabled on the switch for the DHCP Option 82
information to be inserted into packets.
â—† Use the ip dhcp snooping information option command to specify
how to handle DHCP client request packets which already contain
Option 82 information.
EXAMPLE
This example enables the DHCP Snooping Information Option.
Console(config)#ip dhcp snooping information option
Console(config)#
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