Dhcp Snooping Support For Option 82 - HP A5120 EI Series Configuration Manual

Table 4 describes roles of the ports shown in
Table 4 Roles of ports
Device
Switch A
Switch B
Switch C

DHCP snooping support for Option 82

Option 82 records the location information of the DHCP client, so the administrator can locate the DHCP
client for security control and accounting purposes. For more information, see the chapter ―DHCP relay
agent configuration.‖
If DHCP snooping supports Option 82, it handles a client's request according to the contents defined in
Option 82, if any. The handling strategies are described in
If a reply returned by the DHCP server contains Option 82, the DHCP snooping switch removes the
Option 82 before forwarding the reply to the client. If the reply contains no Option 82, the DHCP
snooping switch forwards it directly.
Table 5 Handling strategies of DHCP snooping
If a client's
requesting message
has...
Option 82
no Option 82
Untrusted port
GigabitEthernet 1/0/1
GigabitEthernet 1/0/3 and
GigabitEthernet 1/0/4
GigabitEthernet 1/0/1
Handling
strategy
Drop
Keep
Replace
—
—
—
Figure 31.
Trusted port disabled from
recording binding entries
GigabitEthernet 1/0/3
GigabitEthernet 1/0/1
GigabitEthernet 1/0/3 and
GigabitEthernet 1/0/4
Table
Padding
The DHCP snooping switch will...
format
— Drop the message.
Forward the message without changing
Random
Option 82.
Forward the message after replacing the
normal original Option 82 with the Option 82
padded in normal format.
Forward the message after replacing the
verbose original Option 82 with the Option 82
padded in verbose format.
Forward the message after replacing the
user-defined original Option 82 with the user-defined
Option 82.
Forward the message after adding the Option
normal
82 padded in normal format.
Forward the message after adding the Option
verbose
82 padded in verbose format.
Forward the message after adding the user-
user-defined
defined Option 82.
67
Trusted port enabled to
record binding entries
GigabitEthernet 1/0/2
GigabitEthernet 1/0/2
GigabitEthernet 1/0/2
5.