“Dual Scan” Difficulties with Windows Update on Windows 10 versions 1607 ‘Anniversary update’ and 1703 ‘Creators update’

There is new required reading from Microsoft for all systems administrators who are managing Windows Updates in their organizations. We *strongly* recommend that all of you carefully read the following two articles so that you are aware of this new (and unexpected) behavior of the Windows Update client:

Demystifying “Dual Scan”
Improving Dual Scan on 1607

Microsoft has recently modified the behavior of Windows Update such that if you currently have your clients configured via group policy to point to an internal managed WSUS, it’s possible, depending on how things are configured, that scans for Windows Updates for your target computers might now be bypassing your WSUS and utilizing Microsoft’s public Windows Update servers instead. They describe “Dual Scan” as follows:

It is for the enterprise that wants WU to be its primary update source while Windows Server Update Services (WSUS) provides all other content. In this scenario, the WU client automatically scans against both WSUS and WU, but it only accepts scan results for Windows content from WU. Stated another way, anything on WSUS that resides in the “Windows” product family is ignored by the Dual Scan client. This is to avoid the “two masters” problem that can occur when there are multiple equally valid sources of truth for a given set of updates.


Dual Scan is automatically enabled when a combination of Windows Update group policies [or their MDM equivalents, or the underlying registry keys corresponding to either set of policies] is configured:

  • Specify intranet Microsoft update service location (i.e., WSUS)
  • Either of the policies belonging to Windows Update for Business
    • Select when Feature Updates are received
    • Select when Quality Updates are received

The group policies mentioned above are located in group policy:

Computer Configuration\Administrative Templates\Windows Components\Windows Update\Defer Windows Updates

In my particular case I have ‘Configure Automatic Updates’ and ‘Specify intranet Microsoft update service location’ enabled. These are the two standard/typical policies that any organization will have enabled if they are using a WSUS instead of Windows Update or Microsoft Update.

These two policies are located in group policy:

Computer Configuration\Administrative Templates\Windows Components\Windows Update

Additionally, I also have the ‘Defer feature updates’ setting enabled on my Windows 10 computers. This setting is visible in the ‘Advanced options’ for Window Update Settings control panel, and it’s similar to the group policy ‘Select when Feature Updates are received’ mentioned above.

The behavior that resulted from having the combination of policies described above enabled on my computer is that all of a sudden my scans for Windows Updates were being performed on Microsoft’s public Windows Update server instead of my internal managed WSUS server. Frankly, I was absolutely *shocked* at this change in behavior. We believe that this behavior should not have been automatically enabled by Microsoft but rather should only have been enabled if/when the administrator turned on this capability. However, we obviously have no control over Microsoft, which means that now we instead must just focus on understanding how to effectively disable this behavior.

How to Disable “Dual Scan”

Option 1:
One quick and simple way to disable “Dual Scan” so that your computers will only reach out to your internal WSUS and will not perform scans on the public Windows Update servers is to simply disable ‘Defer feature updates’ or set both of the following two policies to ‘Not configured’

‘Select when Feature Updates are received’
‘Select when Quality Updates are received’

Option 2:
If you want or need to leave one of the policies mentioned in ‘Option 1’ enabled, then you may instead enable a new policy ‘Do not allow update deferral policies to cause scans against Windows Update’. You can find it in group policy:

Computer Configuration\Administrative Templates\Windows Components\Windows Update

The problem, unfortunately, is that this policy exists for Windows 10 version 1607, but at the time of this writing on 2017-09-19 does not yet exist for Windows 10 version 1703. Frustrating, I know!

Additional Notes

  • If you try to enable the ‘Computer Configuration\Administrative Templates\System\Internet Communications Management\Internet Communication settings\Turn off access to all Windows Update features’ group policy then you might start seeing ‘Error -102: Failed to execute the search. HRESULT: -2145124306’ in BatchPatch.
    0x8024002E -2145124306 SUS_E_WU_DISABLED non managed server access is disallowed
  • If you try to enable the ‘Computer Configuration\Administrative Templates\Windows Components\Windows Update\Do not connect to any Windows Update Internet locations’ you might start seeing ‘-102: Failed to execute the search. HRESULT: -2145103860’ in BatchPatch.
    0x8024500C -2145103860
  • In troubleshooting this issue I also encountered ‘-102: Failed to execute the search. HRESULT: -2145123272’ at one point when my WSUS was offline
    0X80240438 -2145123272
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