HP FlexNetwork NJ5000, User Manual

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Figure 245 Trusted and untrusted ports in a cascaded network
Table 91 describes roles of the ports shown in Figure 245 .
Table 91 Roles of ports
Device Untrusted port
Trusted port disabled from
recording binding entries Trusted port enabled to
record binding entries
Switch A GigabitEthernet 1/0/1 GigabitEthernet 1/0/3 GigabitEthernet 1/0/2
Switch B
GigabitEthernet 1/0/3
and GigabitEthernet
1/0/4
GigabitEthernet 1/0/1 GigabitEthernet 1/0/2
Switch C GigabitEthernet 1/0/1
GigabitEthernet 1/0/3 and
GigabitEthernet 1/0/4
GigabitEthernet 1/0/2
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 "
Option 82 ."
DHCP snooping uses the strategies shown in Table 92 to handle Option 82 for DHCP request
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…
Handling strategy The DHCP snooping device…
Option 82
Drop Drops the message.
Keep Forwards the message without changing Option 82.
Replace
Forwards the message after replacing the original
Option 82 with the Option 82 padded in normal format.
No Option 82 N/A
Forwards the message after adding the Option 82
padded in normal format.