Edge-Core ECS4810-12M Layer 2, Management Manual

Page: 772 / 1236

C
HAPTER
26
| General Security Measures
DHCP Snooping
– 772 –
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.
S
YNTAX
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)
D
EFAULT
S
ETTING
Option 82: Disabled
CID/RID sub-type: Enabled
Remote ID: MAC address (hexadecimal)
C
OMMAND
M
ODE
Global Configuration
C
OMMAND
U
SAGE
◆
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.
◆
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.