Whilst working on a Server 2012 RP instance earlier, I needed to enable .NET 3.5 and tried doing so via the roles and features Wizard. I was greeting with a response stating the source media could not be found. It seems the CAB files are not included and are left on the installation media. There is also another requirement to install the .NET 3.5 ServerFeatures component before .NET 3.5 can be installed. To do this you need to run the following DISM commands;
- DISM.EXE /Online /Enable-Feature /FeatureName:NetFX3ServerFeatures /Source:Z:SourcesSXS
- DISM.EXE /Online /Enable-Feature /FeatureName:NetFX3 /Source:Z:SourcesSXS
… where Z is the drive letter of the Server 2012 Media.