Microsoft KB,  Windows Updates

A required device isn’t connected or can’t be accessed – WDS PXE issue

wds error screen

I kept getting “A required device isn’t connected or can’t be accessed” in MDT/WDS.

I had no idea it was actually a cumulative (March) windows update that broke the WDS server this week.

The MS article says “After installing this update, there may be issues using the Preboot Execution Environment (PXE) to start a device from a Windows Deployment Services (WDS) server configured to use Variable Window Extension. This may cause the connection to the WDS server to terminate prematurely while downloading the image. This issue does not affect clients or devices that are not using Variable Window Extension.”


  1. Disable TFTP Variable Window Extension inside WDS properties.

Here is the MS article regarding the issue.

MS are working on a patch soon.

Fixed with the June cumulative update KB4503285 (Server 2012), KB4503276 (Server 2012 R2) KB4503267 (Server 2016) and KB4503327 (Server 2019)

UPDATE 10/07/2019: It appears the June CU KB4503276 for Server 2012 R2, which was meant to fix the PXE booting issue is causing a PXE boot issue in WDS / SCCM

Server 2012 R2 issue has been fixed with KB4512512 on 17/Aug/2019.

Uninstalling the update will fix the issue for now.

If you are using SCCM you can turn on the native SCCM PXE server: Go to Administration > Distribution Points > Open the properties of your DP > PXE Tab > Tick “Enable a PXE responder without Windows Deployment Services”. This will take a few minutes and no reboot is required.

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  • David Rutt

    Dude, you don’t know how much you made my day! This has been messing with me all week. One type of machine would work the other takes a TFTP crap. Unchecked the box, and it is all good.

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    • admin

      Hi David, Great to hear this helped you. The issue I had was related to a win update however it looks like this fix works on other issues like yours. Thanks!

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