Issues with UEFI boot mode enabled

[Kerry Quillen]

In our profiles, we've always had boot mode set to Legacy BIOS.  We've recently started changing that over to UEFI Optimized.  I majority of our servers (blades and DL380-Gen9's & Gen10's) are vm hosts running ESXi 6.7.  The remainder are either Windows 2016 and above or Linux.  The VM hosts boot just fine with UEFI Optimized enabled but the Windows servers hang at a PXE boot screen.  I've read where Windows 2008 must be set to Legacy BIOS but can find nothing about later versions.  Have not tried the Linux servers yet.  

[support_s]

System recommended content:

1. Boot mode comparison: UEFI and Legacy BIOS

2. Advisory: HPE Network Adapters - Preboot eXecution Environment (PXE) Boot with Enabled VLAN Tags Fails In Unified Extensible Firmware Interface (UEFI) Mode

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[ChrisLynch]

You can't just change the boot mode from Legacy to UEFI without reinstalling the OS. Frankly, I am surprised that your ESXi hosts booted.

For Windows and Linux, an EFI image and boot loader must be used, which is not available for legacy boot.