If you are looking to enable SMB large MTU on a Windows Client, you’ll probably start with a Google (or Bing) search. One of the first results is this TechNet article.
From the table you get the impression that to enable large MTU on a client, you need to create a DWORD at HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters with key SMB2 Client Disable Large MTU and set the value to 0.
You would be wrong.
Instead, you need to create a DWORD at HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters with key DisableLargeMtu and set the value to 0, then reset the computer.
That’s an important difference. I’ve poked Jonobie at Microsoft to see if we can get the page updated. She’s kindly added a community feedback post at my request.
Digital Ramblings 
Does not work on Windows 7
Hi Cpeel, Thanks for the suggestions and the work-around. But none of the above mentioned worked for me in Windows 7. I could not see the LargeMTU flag being set. The same worked in Windows2008R2. Any suggestion ?
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