Devices that start up using Preboot Execution Environment (PXE) images from Windows Deployment Services or System Center Configuration Manager may fail to start with error "0xc0000001"

Devices that start up using Preboot Execution Environment (PXE) images from Windows Deployment Services (WDS) or System Center Configuration Manager (SCCM) may fail to start with the error "Status: 0xc0000001, Info: A required device isn't connected or can't be accessed" after installing an affected update on a WDS server.

To mitigate this issue on an SCCM server:

1. Verify Variable Window Extension is enabled. (This setting is not available on Windows Server 2008 SP2 or Windows Server 2008 R2 SP1)
2. Set the values of TFTP block size to 4096 and TFTP window size to 1. For guidance on how to configure them, see Customize the RamDisk TFTP block and window sizes on PXE-enabled distribution points.

Note Try the default values for TFTP block size and TFTP window size first but depending on your environment and overall settings, you may need to adjust them for your setup. You can also try the Enable a PXE responder without Windows Deployment Service setting. For more information on this setting, see Install and configure distribution points in Configuration Manager.

To mitigate this issue on a WDS server without SCCM:

1. In WDS TFTP settings, verify Variable Window Extension is enabled. (This setting is not available on Windows Server 2008 SP2 or Windows Server 2008 R2 SP1)
2. In the Boot Configuration Data (BCD) of the imported image, set RamDiskTFTPBlockSize to 1456.
3. In the BCD of the imported image, set RamDiskTFTPWindowSize to 4.

Note Try the default values for RamDiskTFTPBlockSize and RamDiskTFTPWindowSize first but depending on your environment and overall settings, you may need to adjust them for your setup.

This issue is resolved in the following latest cumulative update (LCU) or Preview of Monthly Rollups released on June 16, 2019 or later:

• KB4512941 LCU for Windows Server, version 1903.
• KB4512534 LCU for Windows Server, version 1809 and Windows Server 2019.
• KB4512509 LCU for Windows Server, version 1803.
• KB4512494 LCU for Windows 10, version 1709.
• KB4512495 LCU for Windows Server, version 1607 and Windows Server 2016.
• KB4512478 Preview of Monthly Rollup for Windows Server 2012 R2.
• KB4512512 Preview of Monthly Rollup for Windows Server 2012.
• KB4512514 Preview of Monthly Rollup for Windows Server 2008 R2 SP1.
• KB4512499 Preview of Monthly Rollup for Windows Server 2008 SP2

We are working on a resolution and will provide an update in an upcoming release for the platforms not already resolved.

Any latest cumulative update (LCU) or Monthly Rollups released on June 11, 2019 or later for the affected platforms may experience this issue:

• KB4503293 LCU for Windows Server, version 1903.
• KB4503327 LCU for Windows Server, version 1809 and Windows Server 2019.
• KB4503286 LCU for Windows Server, version 1803.
• KB4503284 LCU for Windows 10, version 1709.
• KB4503267 LCU for Windows Server, version 1607 and Windows Server 2016.
• KB4503276 Monthly Rollup for Windows Server 2012 R2.
• KB4503285 Monthly Rollup for Windows Server 2012.
• KB4503292 Monthly Rollup for Windows Server 2008 R2 SP1.
• KB4503273 Monthly Rollup for Windows Server 2008 SP2

The following Security Only released on June 11, 2019 for the affected platforms may experience this issue:

• KB4503290 Security-only update for Windows Server 2012 R2.
• KB4503263 Security-only update for Windows Server 2012 and Windows Embedded 8 Standard.
• KB4503269 Security-only update for Windows Server 2008 R2 SP1
• KB4503287 Security-only update for Windows Server 2008 SP2