Enable .NET Framework 3.5 for a local or remote installation of Windows Server 2012 R2.

                  Attempting to Install .NET Framework 3.5 on Windows Server 2012 R2 Fails with Error “the source files could not be downloaded”, even when supplying source.

                       We have application; the application would only works with Framework 3.5, when we attempting to install .Net Framework 3.5 we have received below issue.

Solution

Copy the below source files from your installation media and save it to your desktop or you can specify the path directly when there is installation.

In Server Manager, click Manage and then select Add Roles and Features to start the Add Roles and Features Wizard.

On the Select installation type screen, select Role-based or feature-based installation

Select the target server

On the Select features screen, check the box next to .Net Framework 3.5 Features

On the Confirm installation selections screen, a warning will be displayed asking Do you need to specify an alternate source path?. If the target computer does not have access to Windows Update, click the Specify an alternate source path link to specify the path to the \sources\sxs folder on the installation media and then clickOK. After you have specified the alternate source, or if the target computer has access to Windows Update, click the X next to the warning, and then click Install. 

Installation completed as we expected below.