D-Link DIR-850L User Manual page 42

Section 3 - Configuration
Primary DNS Server: Enter the Primary DNS IP address used here.
Secondary DNS Server: Enter the Secondary DNS IP address used here. This field is normally optional. Only one DNS address is required for
a functional Internet connection, but using a second DNS address provides more stability.
MTU: Maximum Transmission Unit - you may need to change the MTU for optimal performance with your specific ISP.
1400 is the default MTU.
MAC Address: The default MAC Address is set to the Internet port's physical interface MAC address on the Broadband Router. It
is not recommended that 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.
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