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TRENDnet User’s Guide
Industrial Managed Switch Series
57
remote ID or circuit ID. Then the DHCP server echoes the option-82 field in the DHCP
reply.
The DHCP server unicasts the reply to the switch if the request was relayed to the
server by the switch. When the client and server are on the same subnet, the server
broadcasts the reply. The switch verifies that it originally inserted the option-82
data by inspecting the remote ID and possibly the circuit ID fields. The switch
removes the option-82 field and forwards the packet to the switch port that
connects to the DHCP client that sent the DHCP request.
Option Frame Format:
Code
Len
Agent Information Field
82
N
i1
i2
i3
i4
…
iN
The Agent Information field consists of a sequence of SubOpt/Length/Value tuples for
each sub-option, encoded in the following manner:
Sub-Option
Len
Sub-Option Value
1
N
s1
s2
s3
s4
…
sN
DHCP Agent
Sub-Option Description
Sub-option
Code
---------------
----------------------
1
Agent Circuit ID Sub-option
2
Agent Remote ID Sub-option
Circuit ID Sub-option Format:
Sub-Option Type
Length
Information
0x01
Circuit Form
Remote ID Suboption Frame Format:
Sub-Option Type
Length
Type
Length
Mac Address
0x02
8
0
6
6
Circuit Form:
The circuit form is a flexible architecture. It allows user to combine any information or the
system configurations into the circuit sub-option.
The Circuit Form is a string format. And its maximum length is 100 characters.
The keyword, %SPACE, will be replaced with a space character.
The other keywords get system configurations from the system and then replace the
keyword and its leading code in the Circuit form. Eventually, the content of the circuit
form is part of the payload on the DHCP option 82 packet.
Rules:
The keyword must have a leading code ‘%’. For example: %HOSTNAME.
If there are any characters following the keywords, you must add ‘+’ between
the keyword and character. For example: %H/.
If there are any characters before the keyword, you must add ‘+’ between the
character and the keyword. For example: Test+%HOSTNAME.
Keyword:
HOSTNAME
-Add the system name into the Circuit sub-option..
SPACE
-Add a space character.
SVLAN
-Add the service provider VLAN ID into the Circuit sub-option.
If the service provider VLAN is not defined, the system will
return PVLAN.
CVLAN
-Add the customer VLAN ID into the Circuit sub-option.
If the CVLAN is not defined, the system returns 0.
PORT
-Add the transmit port ID into the Circuit sub-option.
FRAME
-Add the frame ID into the Circuit sub-option.
The frame ID is configured with the CLI command, “dhcp-
options option82 circuit_frame VALUE”. Or GUI Circuit Frame.
Summary of Contents for TI-G160WS
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