C
HAPTER
24
| General Security Measures
DHCPv4 Snooping
– 898 –
EXAMPLE
This example enables DHCP snooping for VLAN 1.
Console(config)#ip dhcp snooping vlan 1
Console(config)#
RELATED COMMANDS
ip dhcp snooping (892)
ip dhcp snooping trust (899)
ip dhcp snooping
information option
circuit-id
This command enables the use of DHCP Option 82 information circuit-id
suboption. Use the no form to disable this feature.
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
Disabled
COMMAND MODE
Interface Configuration (Ethernet, Port Channel)
COMMAND USAGE
â—† 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 Command Usage section under
the ip dhcp snooping information option command.
â—† Option 82 information generated by the switch is based on TR-101
syntax as shown below:
The circuit identifier used by this switch starts at sub-option1 and goes
to the end of the R-124 string. The R-124 string includes the following
information:
â–
sub-type - Distinguishes different types of circuit IDs.
â–
sub-length - Length of the circuit ID type
Table 92: Option 82 information
82 3-69 1 1-67 x1 x2 x3 x4 x5 x63
opt82 opt-len sub-opt1 string-len R-124 string
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