Chapter 4: Web management
NS3550-8T-2S Industrial Managed Switch User Manual
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An example of how UPnP devices appear in My Network Places:
DHCP relay
DHCP Relay is used to forward and to transfer DHCP messages between the clients
and the server when they are not on the same subnet domain.
The DHCP option 82 enables a DHCP relay agent to insert specific information into a
DHCP request packets when forwarding client DHCP packets to a DHCP server and
remove the specific information from a DHCP reply packets when forwarding server
DHCP packets to a DHCP client. The DHCP server can use this information to
implement IP address or other assignment policies. Specifically, the option works by
setting two sub-options:
• Circuit ID (option 1). This sub-option should include information specific to which
circuit the request came in on.
• Remote ID (option 2). This sub-option is designed to carry information relating to the
remote host end of the circuit.
The definition of Circuit ID in the switch is four bytes in length and the format is
"vlan_id" "module_id" "port_no". The parameter of "vlan_id" is the first two bytes
representing the VLAN ID. The parameter of "module_id" is the third byte for the
module ID (in a standalone switch it always equals 0; in the switch it means switch ID).
The parameter of "port_no" is the fourth byte and it means the port number.
The remote ID is six bytes in length, and the value equals the DHCP relay agent’s MAC
address. Configure DHCP relay in the DHCP Relay Configuration page.