41-3
Figure 41-3
Extended format of the remote ID sub-option
rnet Switches support
Option 82 in the standard format. Refer to
Figure 41-4
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, S4500 Series Ethe
and
Figure 41-5
for the standard format of the
ub-options (with the default padding contents). In the standard format, the Circuit ID or Remote ID
s
sub-option does not contain the two-byte type and length fields of the circuit ID or remote ID.
Figure 41-4
Standard format of the circuit ID sub-option
Figure 41-5
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
Table 41-1
.
Table 41-1
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.
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
nd is not executed.
the default HEX format if this comma
Circuit ID sub-option
is configured
of the original Option 82 with the configured circuit ID
sub-option in ASCII format.
Forward the packet after replacing the circuit ID sub-option
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.
