Operation Manual – DHCP
H3C S3100 Series Ethernet Switches Chapter 2 DHCP Snooping Configuration
2-4
Figure 2-3 Extended format of the remote ID sub-option
In practice, some network devices do not support the type and length identifiers of the
Circuit ID and Remote ID sub-options. To interwork with these devices, S3100-EI
Series Ethernet Switches support Option 82 in the standard format. Refer to
Figure 2-4
and
Figure 2-5 for the standard format of the sub-options (with the default padding
contents). In the standard format, the Circuit ID or Remote ID sub-option does not
contain the two-byte type and length fields of the circuit ID or remote ID.
Figure 2-4 Standard format of the circuit ID sub-option
Figure 2-5 Standard format of the remote ID sub-option
III. 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
Table 2-1.
Table 2-1 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.
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