Dhcp Relay - Planet GS-5220 Series User Manual

4.2.9 DHCP Relay

Configure DHCP Relay on this page. DHCP Relay is used to forward and 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)
 Remote ID (option 2)
The Circuit ID sub-option is supposed to include information specific to which circuit the request came in on.
The Remote ID sub-option was designed to carry information relating to the remote host end of the circuit.
The definition of Circuit ID in the switch is 4 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. The parameter of "port_no" is the fourth byte and it means the port number.
The Remote ID is 6 bytes in length, and the value equals the DHCP relay agent's MAC address. The DHCP Relay
Configuration screen in Figure 4-2-12 appears.
Figure 4-2-12 DHCP Relay Configuration Page Screenshot
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