DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:C:\Temp
Is your server completely or connected to a WSUS server ?
A common point of confusion is the fact that even on an up-to-date server running Windows Server 2012 R2, a simple attempt to install the .NET Framework 3.5 from the Server Manager will almost certainly fail. This is not a bug, but a design decision by Microsoft. : The source files could not be found
: The source files could not be found. Ensure you are using the media that matches the exact version and build of your installed OS. Missing Media
: Double-check that your /source path points exactly to the directory containing the .cab file, not to the file itself. Ensure the directory path ends with a backslash ( \ ). Error 0x800f0922 Ensure the directory path ends with a backslash ( \ )
Open or Command Prompt as Administrator.
Deployment Scenarios
:If you have the .cab file or the entire sxs folder copied to C:\NetFx3 , run this command in an Elevated Command Prompt :