HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 3 - IP Services Conf - Page 58

DHCP snooping support for Option 82

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Figure 33 Configuring trusted ports in a cascaded network Table 3 Roles of ports Device Switch A Switch B Switch C Untrusted port Trusted port disabled from recording binding entries GigabitEthernet 1/0/1 GigabitEthernet 1/0/3 GigabitEthernet 1/0/3 and GigabitEthernet 1/0/4 GigabitEthernet 1/0/1 GigabitEthernet 1/0/1 GigabitEthernet 1/0/3 and GigabitEthernet 1/0/4 Trusted port enabled to record binding entries GigabitEthernet 1/0/2 GigabitEthernet 1/0/2 GigabitEthernet 1/0/2 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 "Configuring DHCP relay agent." 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 Table 4. If a reply returned by the DHCP server contains Option 82, the DHCP snooping device removes the Option 82 before forwarding the reply to the client. If the reply contains no Option 82, the DHCP snooping device forwards it directly. Table 4 Handling strategies of DHCP snooping If a client's requesting message has... Option 82 Handling strategy Drop Keep Padding format The DHCP snooping device... N/A Random Drops the message. Forwards the message without changing Option 82. 50

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50
Figure 33
Configuring trusted ports in a cascaded network
Table 3
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 of the DHCP client so the administrator can locate the DHCP
client for security control and accounting purposes. For more information, see "
Configuring DHCP relay
agent
."
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
Table 4
.
If a reply returned by the DHCP server contains Option 82, the DHCP snooping device removes the
Option 82 before forwarding the reply to the client. If the reply contains no Option 82, the DHCP
snooping device forwards it directly.
Table 4
Handling strategies of DHCP snooping
If a client's
requesting message
has…
Handling
strategy
Padding format
The DHCP snooping device…
Option 82
Drop
N/A
Drops the message.
Keep
Random
Forwards the message without changing
Option 82.