PLANET WGSW-28040P - Manual (Page 184)

User’s Manual of WGSW-28040 / 28040P / 28040P4
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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 (option2).
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 represent the VLAN ID. The parameter of "module_id" is the third byte for the module ID (in
standalone switch it always equal 0, in stackable switch it means switch 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 is equal the DHCP relay agent’s MAC address. The DHCP Snooping Port
Option82 Setting screen in Figure 4-10-6 appears.
Figure 4-10-6 DHCP Snooping Port Option82 Setting page screenshot
The page includes the following fields:
Object Description
• Port Select port for this drop down list.
• Enable Enables or disables DHCP Option 82 information relay.
(Default: Disabled)
• Action
Sets the DHCP snooping information option policy for DHCP client packets that
include Option 82 information.
• Drop
Discards the Option 82 information in a packet and then floods it to
the entire VLAN.
• Keep
Retain the Option 82 information in the client request, insert the
relay agent’s address (when DHCP snooping is enabled), and
unicast the packet to the DHCP server.