Firstly nested virtualization is the ability to run Hyper-V inside of a virtualized machine (VM). This would allow you to create a VM in a VM, talk about VM-ception! I am intending to build a lab environment to do some practice with the intend to isolate the whole environment away from my actual Home-lab I've got (that would be a topic for another day). So let's move on

So in order to enable Nested Virtualization the following will need to be performed

Note: At this time it is assumed that you have already enabled the Hyper-V Role and created a VM to enable Nested Virtualization.

You will be performing the following
1) Exposing the VM to Virtualized Extension
2) Enabling MAC Spoofing for the Nested VM's NIC

Step 1 : Exposing VM to Virtualized Extensions
Note : VM must be in OFF State

Set-VMProcessor -VMName <VMName> -ExposeVirtualizationExtensions $true

Step 2: Enable MAC Spoofing (GUI)

Right Click the VM --> Properties --> Expand Network Adapter --> Advance Features --> Check Enable MAC address spoofing

Enable MAC Spoofing (Powershell)

Get-VMNetworkAdapter -VMName <VMName> | Set-VMNetworkAdapter -MacAddressSpoofing On

And you're done! You can continue to install Hyper-v Role on the VM and continue!