Microsoftwindowsnetfx3ondemandpackagecab ((better)) Download Server 2012 R2 New -

Run the installation again via Server Manager or DISM without the /Source parameter. Troubleshooting Can not install dotNet 3,5 on Windows Server 2012R2

Once you have the .cab file (typically 200–300 MB), copy it to your target server, e.g., C:\Temp\netfx3.cab . Run the installation again via Server Manager or

Proceed to the page and check .NET Framework 3.5 Features . copy it to your target server