If you have a Windows 8 or 8.1 machine in a domain environment with WSUS and try to add the feature .NET 3.5 framework it may fail with error code 0x800F0906, because it is looking in WSUS which may not host the bits. A lot of people recommend using the media with DISM to install .NET 3.5 offline but I would rather get it from the Cloud because that is what Microsoft wants of its people. Here's how:
On the client machine open gpedit.msc as an administrator.
Browse to Computer Configuration -> Administrator Templates -> System
Open Specify settings for optional component installation and component repair, enable it.
And make the following change:
Save the policy and close gpedit.
Try to add the .NET 3.5 feature now:
