Configuring Option 82
Follow these guidelines when you configure Option 82:
The Option 82 configuration on a Layer 2 Ethernet interface that has been added to an aggregation group does not take effect unless the interface leaves the aggregation group.
To support Option 82, you must configure Option 82 on both the DHCP server and the DHCP snooping device. For information about configuring Option 82 on the DHCP server, see "Enabling handling of Option 82."
If the handling strategy is replace, configure a padding mode and padding format for Option 82. If the handling strategy is keep or drop, you do not need to configure any padding mode or padding format for Option 82. The settings do not take effect even if you configure them.
If Option 82 contains the device name, the device name must contain no spaces. Otherwise, DHCP snooping drops the message. You can use the sysname command to specify the device name. For more information about this command, see Fundamentals Command Reference.
In verbose mode, DHCP snooping pads the VLAN ID field of sub-option 1 in the format of outer VLAN tag.inner VLAN tag in either of the following situations:
DHCP snooping and QinQ work together.
A DHCP packet contains two VLAN tags.
For example, if the outer VLAN tag is 10 and the inner VLAN tag is 20, the VLAN ID field is 000a.0014. The hexadecimal digit a represents the outer VLAN tag 10, and the hexadecimal digit 14 represents the inner VLAN tag 20.
The device name (sysname) must not include spaces if it is configured as the padding content for sub-option 1. Otherwise, the DHCP snooping device will fail to add or replace Option 82.
To configure DHCP snooping to support Option 82:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Enable DHCP snooping to support Option 82. | dhcp snooping information enable | By default, DHCP snooping does not support Option 82. |
4. (Optional.) Configure a handling strategy for DHCP requests that contain Option 82. | dhcp snooping information strategy { drop | keep | replace } | By default, the handling strategy is replace. |
5. (Optional.) Configure the padding mode and padding format for the Circuit ID sub-option. | dhcp snooping information circuit-id { [ vlan vlan-id ] string circuit-id | { normal | verbose [ node-identifier { mac | sysname | user-defined node-identifier } ] } [ format { ascii | hex } ] } | By default, the padding mode is normal and the padding format is hex for the Circuit ID sub-option. |
6. (Optional.) Configure the padding mode and padding format for the Remote ID sub-option. | dhcp snooping information remote-id { normal [ format { ascii | hex } ] | [ vlan vlan-id ] string remote-id | sysname } | By default, the padding mode is normal and the padding format is hex for the Remote ID sub-option. |