.Net Framework Installation Error – You Need to Specify an Alternate Source File Path
Command line to Install .NET Framework on 2012 server
Insert the Windows 2012 DVD into the drive or if the server is VM mount the iso file through the VM properties or mount the DVD using another tool like WinCDEMU.
Run the following command from an elevated command prompt:
Dism /online /enable-feature /featurename:NetFx3 /All /Source:<drive>:\sources\sxs /LimitAccess