Dhcp Snooping Support For Option 82 - HP FlexNetwork NJ5000 User Manual

Figure 245 Trusted and untrusted ports in a cascaded network
Table 91 describes roles of the ports shown in
Table 91 Roles of ports
Device
Switch A
Switch B
Switch C

DHCP snooping support for Option 82

Option 82 records the location information about the DHCP client so the administrator can locate the
DHCP client for security and accounting purposes. For more information, see
DHCP snooping uses the strategies shown in
messages. If a response returned by the DHCP server contains Option 82, DHCP snooping removes
Option 82 before forwarding the response to the client. If the response contains no Option 82, DHCP
snooping forwards it directly.
Table 92 Handling strategy
If a DHCP request
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
N/A
Figure 245.
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 92
The DHCP snooping device...
Drops the message.
Forwards the message without changing Option 82.
Forwards the message after replacing the original
Option 82 with the Option 82 padded in normal format.
Forwards the message after adding the Option 82
padded in normal format.
238
Trusted port enabled to
record binding entries
GigabitEthernet 1/0/2
GigabitEthernet 1/0/2
GigabitEthernet 1/0/2
"Option
to handle Option 82 for DHCP request
82."