CLI Reference Guide-R05

Chapter 9 | General Security Measures
DHCP Snooping
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Command Mode
Global Configuration
Command Usage
◆ When DHCP snooping is enabled globally using the ip dhcp snooping
command, and enabled on a VLAN with this command, DHCP packet filtering
will be performed on any untrusted ports within the VLAN as specified by the ip
dhcp snooping trust command.
◆ When the DHCP snooping is globally disabled, DHCP snooping can still be
configured for specific VLANs, but the changes will not take effect until DHCP
snooping is globally re-enabled.
◆ When DHCP snooping is globally enabled, and then disabled on a VLAN, all
dynamic bindings learned for this VLAN are removed from the binding table.
Example
This example enables DHCP snooping for VLAN 1.
Console(config)#ip dhcp snooping vlan 1
Console(config)#
Related Commands
ip dhcp snooping (305)
ip dhcp snooping trust (313)
ip dhcp snooping
information option
circuit-id
This command specifies DHCP Option 82 circuit-id suboption information. Use the
no form to use the default settings.
Syntax
ip dhcp snooping information option circuit-id string string
no dhcp snooping information option circuit-id
string - An arbitrary string inserted into the circuit identifier field.
(Range: 1-32 characters)
Default Setting
VLAN-Unit-Port
Command Mode
Interface Configuration (Ethernet, Port Channel)
Command Usage
◆ DHCP provides a relay mechanism for sending information about the switch
and its DHCP clients to the DHCP server. DHCP Option 82 allows compatible
DHCP servers to use the information when assigning IP addresses, to set other
services or policies for clients. For more information of this process, refer to the