D-Link DGS-6600-48TS Configuration Guide - Page 502

Volume 9-Network Application / Chapter 50-DHCP Relay Configuration DHCP Relay Configuration Commands Enter the following command in global configuration mode to globally enable the insertion of the relay agent information option (option 82) in an IP packet: Command ip dhcp relay information option Explanation Enables the insertion of the relay agent information option. In the following example, the user enables the insertion of the relay information option (option-82) for relayed DHCP request packets: DGS-6600:2>enable DGS-6600:15#configure terminal DGS-6600:15(config)#ip dhcp relay information option DGS-6600:15(config)#end Specifying the Policy for Inserting the Relay Agent Information Option If the device is already configured to insert the relay agent information option, but the received DHCP message that will be relayed already has the option-82 field encoded, the user can specify the action for the message. The user can specify to drop the message, leave the option-82 field untouched, or replace the field with a new option-82 value. Enter the following command in global configuration mode to configure the information re-forwarding policy for the DHCP relay agent: Command ip dhcp relay information policy {drop | keep | replace} Explanation Configures the information re-forwarding policy for the DHCP relay agent. In the following example, the user sets the IP DHCP relay information policy to drop any DHCP request packets that were relayed by other DHCP agents and already have the DHCP option-82 inserted: DGS-6600:2>enable DGS-6600:15#configure terminal DGS-6600:15(config)#ip dhcp relay information policy drop DGS-6600:15(config)#end Checking the Validity of Reply Messages By default, the relay agent will check the validity of the option-82 field in the reply DHCP message and drop the invalid messages. The user can disable this checking function and forward all of the relay messages. DGS-6600 Configuration Guide 502