This blog post was originally written by Michael Schroeder.
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Today, there are a lot of applications and utilities available that leverage the .NET 3.5 framework to function properly. With Windows Server 2012, Microsoft provides both the .NET 3.5 and 4.5 install options for any of your applications’ requirements. When installing the .NET 3.5 components, you must pay careful attention to a few details.
When using Server Manager to install the .NET 3.5 feature you may run into the following message indicating the source files could not found:
Using PowerShell to install, we see a similar message stating “The source files could not be downloaded” along with the error 0x800f0906. In my case, the server is not connected to the internet to access the Windows Update servers.
Going back and looking more closely at the Add Roles and Features wizard, you’ll see a warning at the top asking the following and also providing a “Specify an alternate source path” link at the bottom of the wizard.
Why do we need to provide source files for this feature and not others? After running the following PowerShell command on a Full GUI install, we see the install state is set to “Removed” for these components. The “Removed” install state indicates that the feature files are not available on the local server. This is the default for all editions of Windows Server 2012.
For those servers without a WSUS server present or a connection to Windows Update, where the necessary components can be retrieved, we’ll need to provide an alternate source path to the side-by-side store (sxs) on the Windows Server installation media to complete the feature installation.
We can choose one of the following installation methods:
1. Using the Add Roles and Features Wizard, specify an alternate source path using the link at the bottom of the wizard. For example, D: is my Windows Server DVD media.
2. Using PowerShell, specify the source files path when installing.
Install-WindowsFeature NET-Framework-Core –Source D:\Sources\sxs
3. Using DISM from the command prompt, specify the source files path parameter:
DISM /Online /Enable-Feature /FeatureName:NetFx3 /Source:d:\sources\sxs
4. Using a file share containing the sxs folder, specify the unc share path:
Install-WindowsFeature NET-Framework-Core –Source \\ServerName\ShareName\sxs
TechNet: Install or Uninstall Roles, Role Services, or Features
It's always good to find a quick answer to an annoying problem like this when you're trying to get a new server online ASAP.