Chapter 9
| General Security Measures
DHCPv4 Snooping
– 285 –
switch receives any messages from a DHCP server, any packets received from
untrusted ports are dropped.
Example
This example enables DHCP snooping globally for the switch.
Console(config)#ip dhcp snooping
Console(config)#
Related Commands
ip dhcp snooping vlan (291)
ip dhcp snooping trust (295)
ip dhcp snooping
information option
This command enables the use of DHCP Option 82 information for the switch, and
specifies the frame format to use for the remote-id when Option 82 information is
generated by the switch. Use the
no
form without any keywords to disable this
function, the no form with the encode no-subtype keyword to enable use of sub-
type and sub-length in CID/RID fields, or the
no
form with the
remote-id
keyword
to set the remote ID to the switch’s MAC address encoded in hexadecimal.
Syntax
ip dhcp snooping information option
[
encode no-subtype
] [
remote-id
{
ip-address
[
encode
{
ascii
|
hex
}] |
mac-address
[
encode
{
ascii
|
hex
}] |
string
string}]
no ip dhcp snooping information option
[
encode no-subtype
]
[
remote-id
[
ip-address
encode
] | [
mac-address
encode
]]
encode
no-subtype
- Disables use of sub-type and sub-length fields in
circuit-ID (CID) and remote-ID (RID) in Option 82 information.
mac-address
- Inserts a MAC address in the remote ID sub-option for the
DHCP snooping agent (that is, the MAC address of the switch’s CPU).
ip-address
- Inserts an IP address in the remote ID sub-option for the DHCP
snooping agent (that is, the IP address of the management interface).
encode
- Indicates encoding in ASCII or hexadecimal.
string - An arbitrary string inserted into the remote identifier field.
(Range: 1-32 characters)
Default Setting
Option 82: Disabled
CID/RID sub-type: Enabled
Remote ID: MAC address (hexadecimal)
Command Mode
Global Configuration
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