H3C Technologies H3C S3100 Series Switches - Manual (Page 536)

3-4
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 .
Figure 3-6 Ways of handling a DHCP packet with Option 82
Handling
policy
Sub-option
configuration
The DHCP Snooping device will…
Drop — Drop the packet.
Keep — Forward the packet without changing Option 82.
Neither of the two
sub-options is
configured
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.
Circuit ID sub-option is
configured
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.
Replace
Remote ID sub-option
is configured
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.
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 .
Figure 3-7 Ways of handling a DHCP packet without Option 82
Sub-option configuration The DHCP-Snooping device will …
Neither of the two
sub-options is configured.
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.
Circuit ID sub-option is
configured. Forward the packet after adding Option 82 with the configured circuit
ID sub-option in ASCII format.
Remote ID sub-option is
configured. Forward the packet after adding Option 82 with the configured remote
ID sub-option in ASCII format.