Method 1: Extract from Original Installation Media (Recommended)
The solution is to use the microsoft-windows-netfx3-ondemand-package.cab file, which contains the necessary installation files. 1. What is the NetFx3 OnDemand Package? Instead, locate your original Windows Server 2012 R2
Instead, locate your original Windows Server 2012 R2 installation media (ISO). The file on that media remains the definitive, digitally signed, and safe version. Use modern deployment tools (DISM, PowerShell) to install from that source—this is the fastest, most reliable, and secure method in any environment, new or legacy. : If you have the ISO or physical
: If you have the ISO or physical DVD, the file is located in the \sources\sxs directory. For more detailed troubleshooting
DISM.exe /online /enable-feature /featurename:NetFX3 /All /Source:C:\dotnet35 /LimitAccess Use code with caution. Copied to clipboard /LimitAccess flag is critical; it tells Windows
If you do not have the installation media, you can force the server to download the files from Microsoft: Open ( gpedit.msc ).
For more detailed troubleshooting, you can refer to official documentation from Microsoft Learn or community discussions on Server Fault exact registry keys needed to temporarily bypass WSUS during this installation? Installing .Net 3.5 on Windows 2012 R2 - Server Fault