H3C S5600 Series Operation Manual page 781

Operation Manual – DHCP
H3C S5600 Series Ethernet Switches
The remote ID type field and circuit ID type field are determined by the option storage
format. They are both set to 0 in the case of HEX format and to 1 in the case of ASCII
format.
Figure 4-2 Extended format of the circuit ID sub-option
Figure 4-3 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, S5600 Series
Ethernet Switches support Option 82 in the standard format. Refer to
Figure 4-5
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 4-4 Standard format of the circuit ID sub-option
Figure 4-5 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
for the standard format of the sub-options (with the default padding contents).
Table
Chapter 4 DHCP Snooping Configuration
4-1.
4-3
Figure 4-4 and