H3C S3100 Series Operation Manual page 536

Figure 3-5 Standard format of the remote ID sub-option
Mechanism of DHCP-snooping Option 82
With DHCP snooping and DHCP-snooping Option 82 support enabled, when the DHCP snooping
device receives a DHCP client's request containing Option 82, it will handle the packet according to the
handling policy and the configured contents in sub-options. For details, see
Figure 3-6 Ways of handling a DHCP packet with Option 82
Handling
policy
Drop —
Keep —
Neither of the two
sub-options is
configured
Replace
Circuit ID sub-option is
configured
Remote ID sub-option
is configured
When receiving a DHCP client's request without Option 82, the DHCP snooping device will add the
option field with the configured sub-option and then forward the packet. For details, see
Figure 3-7 Ways of handling a DHCP packet without Option 82
Sub-option configuration
Neither of the two
sub-options is configured.
Circuit ID sub-option is
configured.
Remote ID sub-option is
configured.
Sub-option
configuration
Drop the packet.
Forward the packet without changing Option 82.
Forward the packet after replacing the original Option
82 with the default content.
The storage format of Option 82 content is the one
specified with the dhcp-snooping information
format command or the default HEX format if this
command is not executed.
Forward the packet after replacing the circuit ID
sub-option of the original Option 82 with the configured
circuit ID sub-option in ASCII format.
Forward the packet after replacing the remote ID
sub-option of the original Option 82 with the configured
remote ID sub-option in ASCII format.
The DHCP-Snooping device will ...
Forward the packet after adding Option 82 with the default contents.
The format of Option 82 is the one specified with the dhcp-snooping
information format command or the default HEX format if this
command is not executed.
Forward the packet after adding Option 82 with the configured circuit
ID sub-option in ASCII format.
Forward the packet after adding Option 82 with the configured remote
ID sub-option in ASCII format.
3-4
Figure
The DHCP Snooping device will...
3-6.
Figure 3-7.