trying to activate the .net 3.5 feature in Windows 8/8.1 can end with errors 0x800F0906 or 0x800F081F. this error shows up even when using the dism command line tool "DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:d:\sources\sxs" as described in Installing the .NET Framework 3.5 on Windows 8 or 8.1 ( ).

Both the GUI and the DISM command (without the /LimitAccess Switch) will try to get needed files from the internet, however, in the enterprise, chances are those requests end at your WSUS server, which not neccessarily has the files needed. You can set up your PC to contact the microsoft server instead, either by GPO or with gpedit.msc. Check the setting "Computer Configuration\Administrative Templates\System\Specify settings for optional component installation and component repair".

If your enterprise requires the option for offline installation of the feature, you can use the above method to install one PC and activate the feature via internet, afterwards make a copy of the %windir%\winsxs available in your network and use that folder as source (eg /source:\\yourserver\yourshare\winsxs) when activating the feature via dism