I was in process of installing a new software on my Windows Server 2012 R2 and the software requires to have .Net 3.5 Framework installed and enabled on the server. I have tried to enable the feature via the Administrator console but the installation failed even the D: drive has the Windows Server 2012 installation media mounted.
So here is simple command line that helped me and fixed the issue very quickly on my Windows Server 2012 R2 and installed the framework for me:
Install-WindowsFeature –name NET-Framework-Core –source D:\sources\sxs
This command line did the trick and installed the framework without issue.
Installed the Framework and not required reboot. Now I can proceed with previous installation of additional software on the server as planned.