D-Link DIR-68 User Manual page 27

Section  - Configuration
MTU: Maximum Transmission Unit - you may need to change the MTU for optimal performance with your specific ISP. 1400 is the default
MTU.
Clone MAC The default MAC Address is set to the Internet port's physical interface MAC address on the Broadband Router. It is not recommended that
Address:
you change the default MAC address unless required by your ISP. You can use the Clone.Your.PC's.MAC.Address button to replace the
Internet port's MAC address with the MAC address of your Ethernet card.
D-Link DIR-68 User Manual 7