2 describes roles of the ports shown in a.
2.Roles of ports
Device | Untrusted port | Trusted port disabled from | Trusted port enabled to | |
recording binding entries | 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 1/0/1 | GigabitEthernet 1/0/2 | |
GigabitEthernet 1/0/4 | ||||
|
|
| ||
|
|
|
| |
Switch C | GigabitEthernet 1/0/1 | GigabitEthernet 1/0/3 and | GigabitEthernet 1/0/2 | |
GigabitEthernet 1/0/4 | ||||
|
|
| ||
|
|
|
|
DHCP snooping support for Option 82
Option 82 records the location information of the DHCP client. The administrator can locate the DHCP client to further implement security control and accounting. For more information, see the chapter “DHCP overview”.
If DHCP snooping supports Option 82, it will handle a client’s request according to the contents defined in Option 82, if any. The handling strategies are described in the table below.
If a reply returned by the DHCP server contains Option 82, the DHCP snooping device will remove the Option 82 before forwarding the reply to the client. If the reply contains no Option 82, the DHCP snooping device forwards it directly.
If a client’s requesting | Handling | The DHCP snooping device will… | |
message has… | strategy | ||
| |||
| Drop | Drop the message. | |
|
|
| |
Option 82 | Keep | Forward the message without changing Option 82. | |
|
| ||
Replace | Forward the message after replacing the original Option 82 | ||
| |||
| with the Option 82 padded in normal format. | ||
|
| ||
|
|
| |
no Option 82 | — | Forward the message after adding the Option 82 padded in | |
normal format. | |||
|
| ||
|
|
|
Complete the following tasks to configure DHCP snooping:
TaskRemarks
Enabling DHCP snooping
Required
By default, DHCP snooping is disabled.
290