Configuring option 82 – H3C Technologies H3C S5560 Series Switches User Manual
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Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enable DHCP snooping.
dhcp snooping enable
By default, DHCP snooping is
disabled.
3.
Enter interface view.
interface interface-type
interface-number
This interface must connect to the
DHCP server.
4.
Specify the port as a trusted
port.
dhcp snooping trust
By default, all ports are untrusted
ports after DHCP snooping is
enabled.
5.
Return to system view.
quit
N/A
6.
Enter interface view.
interface interface-type
interface-number
This interface must connect to the
DHCP client.
7.
(Optional.) Enable recording
of DHCP snooping entries.
dhcp snooping binding record
By default, after DHCP snooping is
enabled, recording of DHCP
snooping entries is disabled.
Configuring Option 82
Follow these guidelines when you configure Option 82:
•
If you configure Option 82 on a Layer 2 Ethernet interface that has been added to an aggregation
group, the settings do not take effect unless the interface is removed from 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 "
•
If the handling strategy is configured as replace, you must configure a padding format for Option
82. If the handling strategy is keep or drop, there is no need to configure any padding format.
•
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 for
Option 82 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.
•
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 fails 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