Enabling nested Virtualisation in Hyper-V 2016

Overview

In some scenarios, running a virtual host inside an existing virtual host can prove to be useful especially in a lab environment where you don't have the space or budget to have a bunch of physical machines for this kind of experiment.

Thankfully Hyper-V more recently has had the ability to do this.

The problem

You have managed to install the Hyper-V role on a physical Windows server and then virtualized it with the Hyper-V role and some of the VMs intact. 

But the VMs won't start as it won't be able to find the VT (Virtualisation Technology) of the host's CPU as this type of option is not needed to be passed through to a VM.

You could also try and enable the role on an existing VM but you may get an error similar to what we see below.

Enabling VT Passthrough

In this example the name of the VM is TEST SERVER 2 and the test server is conveniently called PYMDC01 (which is also a DC).

Ensure the VM is shutdown and does not have dynamic memory enabled

Go to the host and open powershell to run the following command:

Set-VMProcessor -VMName "TEST SERVER 2" -ExposeVirtualizationExtensions $true

You should see it complete without any errors.

We can now see the role installs without any issues and even proceed to load a VM inside of it.