QTECH
Software Configuration Manual
11-157
The form of sub-option1is as following :
The form of sub-option2 is as following :
11.5.3.1
Introduction to option 82 supporting
Option 82 is a relay agent information option in DHCP packets. When a request packet from a DHCP client
travels through a DHCP relay agent on its way to the DHCP server, the DHCP relay agent adds option 82 into the
request packet. Option 82 includes many sub-options, but the DHCP server supports only sub-option 1 and sub-option
2 at present. Sub-option 1 defines agent circuit ID (that is, Circuit ID) and sub-option 2 defines remote agent ID (that
is, Remote ID).
Option 82 enables a DHCP server to track the address information of DHCP relay agents, through which and
other proper software, you can achieve the DHCP assignment limitation and accounting functions.
11.5.3.2
Primary terminologies
·
Option : A length-variable field in DHCP packets, carrying information such as part of the lease
information and packet type. It includes at least one option and at most 255 options.
·
Option 82 : Also known as relay agent information option. This option is a part of the Option field in
DHCP packet. According to RFC3046, option 82 lies before option 255 and after the other options.
Option 82 includes at least one sub-option and at most 255 sub-options. Currently, the commonly used
sub-options in option 82 are sub-option 1 and sub-option 2.
·
Sub-option 1 : A sub-option of option 82. Sub-option 1 represents the agent circuit ID, namely
Circuit ID. It holds the port number and VLAN-ID of the switch port connected to the DHCP client, and
is usually configured on the DHCP relay agent. Generally, sub-option 1 and sub-option 2 must be used
together to identify information about a DHCP source.
·
Sub-option 2 : A sub-option of option 82. Sub-option 2 represents the remote agent ID, namely
Remote ID. It holds the MAC address of the DHCP relay agent, and is usually configured on the DHCP
relay agent. Generally, sub-option 1 and sub-option 2 must be used together to identify information
about a DHCP source.
0002
Sub Type
06
Sub Length
001fce115100
MAC Address
01
04
0065
00
02
Sub Type
Sub Length
VLAN ID
Slot
Port