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What is nested virtualization in Microsoft Hyper‑V?

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Well,

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nested virtualization is a capability of the Hyper‑V host in which you can

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allow virtual machines to act as a Hyper‑V host itself.

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Now, in a hybrid administration standpoint, you think about Azure. Okay,

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when I create a virtual machine in Azure,

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that's a Hyper‑V VM I can presume, right? But what if you had need to host VMs

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in a nested capacity? There are selected Azure virtual machine role sizes that

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support nested virtualization. So you can stand up Hyper‑V hosts in Azure

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virtual machines. If you want more information on which Azure VM sizes are in

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scope, check the exercise files. Now the host on which you want to enable

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nested virtualization must support CPU virtualization extensions, either Intel

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or AMD. That should be a no‑brainer given you have a Hyper‑V host running. You

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can enable nested virtualization on the host for a particular VM using

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PowerShell. Specifically, this is the Hyper‑V PowerShell command

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Set‑VMProcessor, where you target a particular VM and you set

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ExposeVirtualizationExtensions to true. That's what you have to do once per VM

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on the Hyper‑V host. You also have to modify the virtual switch on the host to

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allow media access control or MAC address spoofing. Why?

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Because when you're doing nested virtualization,

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you're going to have the top‑level Hyper‑V host, and then you've got

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your collection of Hyper‑V top‑level virtual switches.

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A VM that's enabled for nested will become a Hyper‑V host itself inside the

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main host, and we'll have a second layer of switches. So thus, you need to

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be much more gracious or much more liberal,

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I guess, in terms of your MAC address tolerance and security.

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You need to relax those controls a little bit. Let's do a demo.