Configuring DHCP snooping support for Option 82
Restrictions and guidelines
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 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.
DHCP snooping uses "outer VLAN tag.inner VLAN tag" to fill the VLAN ID field of sub-option 1 in verbose padding format if either of the following conditions exists:
DHCP snooping and QinQ work together.
DHCP snooping receives a DHCP packet with 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.
Procedure
Enter system view.
system-view
Enter interface view.
interface interface-type interface-number
Enable DHCP snooping to support Option 82.
dhcp snooping information enable
By default, DHCP snooping does not support Option 82.
(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.
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.
(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.
If the device name (sysname) is configured as the padding content for sub-option 1, make sure the device name does not include spaces. Otherwise, the DHCP snooping device will fail to add or replace Option 82.
(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.