If you have an application that you want to run on Windows Server 2012 that requires the .NET Framework 3.5 (like Microsoft Exchange Server 2010), you will most likely run in to a problem when trying to install it. If you are trying to install .NET Framework 3.5 from the Server Manager GUI, you will see this when installing the feature:
“Do you want to specify an alternate source path? One or more installation selections are missing source files…”
To solve this, you can either:
1. Go to a command prompt and enter this:
dism /online /enable-feature /featurename:NetFX3 /all /Source:d:\sources\sxs /LimitAccess
Note: D: is the source location. 2012 DVD most of the time.
2. Go down to “Specify an alternate source path” and enter “d:\sources\sxs” as the path.
Now you should see this under your Features list: