If mounting a https://www.microsoft.com/en-us/evalcenter/evaluate-windows-server-2012-r2 still fails, We determined a minor tweak to Eis's SUPERB INSTRUCTIONS March 19th/2016 was the last inch for success.
Downloading and mounting 2012 Server R2 install ISO is key, but we had to switch to the mounted drive letter\sources directory and load the NEWER R2 v9600 version of the DISM executable. Just mounting the ISO and specifying the /source location failed to complete or even initiate any progress of installation since Windows was using the version 9200 of DISM that apparently hates the /source switch but only reported as much inside the %systemroot%\Logs\DISM\dism.log.
The error explicitly described /sources as and UNKNOWN switch and thus was doomed to silent failure without properly mounting the R2 source ISO.
It was necessary to hard specify the newer version of DISM.exe 9600 inside the mounted ISO by changing directories to the mounted ISO path of dism.exe.
cd /d d:\sources && .\dism.exe /online /enable-feature featurename:NetFX3ServerFeatures **/Source**:d:\sources\sxs /LimitAccess
cd /d d:\sources && .\dism.exe /online /enable-feature /featurename:NetFX3 **/Source**:d:\sources\sxs /LimitAccess
The command processor output will immediately specify whether you're executing the required version of dism.exe
*Deployment Image Servicing and Management tool
**Version: 6.3.9600.17031**
Image Version: 6.2.9200.16384
Enabling feature(s)
[==========================100.0%==========================]
The operation completed successfully.
Restart Windows to complete this operation.
Do you want to restart the computer now? (Y/N) n*
This was executed on a freshly turned up 2012 Server with only the Windows Update Agent v2 installed:
Windows Update Agent 7.8.9200.16927
Windows Update Agent 7.8.9200.16924
Windows Update Agent 7.8.9200.16927
Installation date: 01312017 1304PM
Installation status: Succeeded
Windows Update Agent 7.8.9200.16927
Installation date: 01312017 1304PM
Installation status: Succeeded
Extract it using the DISM tool to a folder location with a computer that does have access a installation media and/or access to the internet. Once it is placed into the component store it can be extracted. – Ramhound – 2014-12-10T17:41:48.597
Possible duplicate of Installing .NET framework 3.5 on windows server 2012
– eis – 2016-03-09T15:00:52.123