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 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. | |
Replace | normal | Forwards the message after replacing the original Option 82 with the Option 82 padded in normal format. | |
verbose | Forwards the message after replacing the original Option 82 with the Option 82 padded in verbose format. | ||
user-defined | Forwards the message after replacing the original Option 82 with the user-defined Option 82. | ||
Append | normal | Forwards the message without changing Option 82. | |
verbose | Forwards the message without changing Option 82. | ||
private | Forwards the message after adding sub-option 9 to option 82 or adding content to sub-option 9 that option 82 contains. | ||
standard | Forwards the message without changing Option 82. | ||
user-defined | Forwards the message without changing Option 82. | ||
no Option 82 | N/A | normal | Forwards the message after adding the Option 82 padded in normal format. |
N/A | private | Forwards the message after adding the Option 82 padded in private format. | |
N/A | standard | Forwards the message after adding the Option 82 padded in standard format. | |
N/A | verbose | Forwards the message after adding the Option 82 padded in verbose format. | |
N/A | user-defined | Forwards the message after adding the user-defined Option 82. |
The handling strategy and padding format for Option 82 on the DHCP snooping device are the same as those on the relay agent.