As specified in RFC, duplicate Options are not recommended in a DHCP packet if the length of the Option field in the DHCP packet does not exceed 255 bytes. However, different vendors process the Option field differently. DHCP response packets sent from some servers may contain duplicate options, such as Option 3 and Option 51.

        In some versions, after DHCP is enabled using the dhcp enable command, the switch drops received DHCP packets with duplicate options.
        In V100R003 and earlier versions, the switch does not check for duplicate options in DHCP packets. In V100R005, the switch checks for duplicate options in DHCP packets by default. In V100R006 and later versions, the switch does not check for duplicate options in DHCP packets by default. You can run the dhcp anti-attack check duplicate option command in the system view to enable the switch to check for duplicate options in DHCP packets.