If you use a digital subscriber line (DSL), adjusting your router's MTU setting as described below may resolve connectivity issues. For more information or detailed instructions about changing your router's MTU setting, please contact your router's manual or contact your internet service provider.
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To allow transmitting large files, set the MTU to 1492.
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To determine whether communications protocol overhead is an issue, follow the procedure below for your Windows system.
Windows 7 or Vista
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Click Start.
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At the Start Search field, type the command below. (Use lowercase letters. The letter after the first hyphen (-) is a lowercase L.)
ping -l 1472 -f ftpfp.quicken.com
If the "Packet needs to be fragmented but DF set" message appears in the window, set your router's MTU to 1492.

Windows XP
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On the Start menu, select Run.
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At the Open field, type the command below. (Use lowercase letters. The letter after the first hyphen (-) is a lowercase L.)
ping -l 1472 -f ftpfp.quicken.com
If the "Packet needs to be fragmented but DF set" message appears in the window, set your router's MTU to 1492.

For additional information, click here to read "How to change the PPPoE MTU size in Windows XP."