Chapter 9
| General Security Measures
DHCPv4 Snooping
– 341 –
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
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 82 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.
â—† When the DHCP Snooping Information Option is enabled, clients can be
identified by the switch port to which they are connected rather than just their
MAC address. DHCP client-server exchange messages are then forwarded
To Next Page
Loading...
Need help?
General