How to Enable Nested ESXi & Other Hypervisors in vSphere 5.1

Posted on 08/29/2012 by William Lam

There are a ton of new features with the latest release of vSphere 5.1, but the one “unsupported” feature I always test first is “Nested Virtualization” (aka Nested ESXi) and with the latest release, it seems to have gotten even better. You will still need to have the same physical CPU prerequisites as you did in the past to run “Nested Virtualization” as well as nesting 64-bit VMs.

  • Intel VT-x or AMD-V is required for running “Nested Virtualization” which supports nested 32-bit VMs
  • Intel EPT or AMD RVI is required for running nested 64-bit VMs.

A quick way to verify whether your CPU truly supports both Intel-VT+EPT or AMD-V+RVI, you can paste the following into a browser:  


You will need to login with your root credentials and then look for the “nestedHVSupported” property and if it states false, it means you maybe able to install nested ESXi or other hypervisor, but you will not be able to run nested 64-bit VMs, only 32-bit VMs, assuming you have either Intel-VT or AMD-V support on your CPUs.

For more details, take a look at this article for troubleshooting: Having Difficulties Enabling Nested ESXi in vSphere 5.1?

Disclaimer: This is not officially supported by VMware, please use at your own risk.

There are some changes with Nested Virtualization in vSphere 5.1 also officially known as VHV (Virtual Hardware-Assisted Virtualization). If you are using vSphere 5.0 to run Nested ESXi or other nested Hypervisors, then please take a look at the instructions in this article. With vSphere 5.1, there have been a few minor changes to enable VHV.

  1. The new Virtual Hardware 9 compatibility will be required when creating your nested ESXi VM, Virtual Hardware 8 will not work if you are running ESXi 5.1 on your physical host. You will still need to enable promiscuous mode on the portgroup that will be used for your nested ESXi VM for network connectivity.
  2. vhv.allow = “true” is no longer valid for ESXi 5.1 to enable VHV. A new parameter has been introduced calledvhv.enable = “true” that is now defined on a per VM basis to provide finer granularity of VHV support. This also allows for better portability between VMware’s hosted products such as VMware Fusion and Workstation as they also support the vhv.enable parameter.
  3. You can now enable VHV on a per VM basis and using the new vSphere Web Client which basically adds thevhv.enable = “true” parameter to the VM’s .VMX configuration file.

Note: You can run a nested ESXi 5.1 VM on top of a physical ESXi 5.0 host, just follow the instructions here.

Enabling VHV (Virtual Hardware-Assisted Virtualization)

Step 1 – Create a new Virtual Hardware 9 Virtual Machine using the new vSphere Web Client that’s available with vCenter Server 5.1.

Step 2 – Select “Linux” as the guestOS Family and “Other Linux (64-bit)” as the guestOS Version.

Step 3 – During the customize hardware wizard, expand the “CPU” section and select “Hardware Virtualization” box to enable VHV.

Note: If this box is grayed out, it means that your physical CPU does not supported Intel VT-x + EPT or AMD-V + RVI which is required to run VHV OR that you are not using Virtual Hardware 9. If your CPU only supports Intel-VT or AMD-V, then you can still install nested ESXi, but you will only be able to run nested 32-bit VMs and not nested 64-bit VMs.

Step 4 – It is still recommended that you change the guestOS Version to VMware ESXi 5.x after you have created the VM shell, as there are some special settings that are applied automatically. Unfortunately with the new vSphere Web Client, you will not be able to modify the guestOS after creation, so you will need to use the C# Client OR manually go into the .VMX and update guestOS = “vmkernel5″

Now you are ready to install nested ESXi VMs as well as run nested 64-bit VMs within.

If you have followed my previous article about How to Enable Support for Nested 64bit & Hyper-V VMs in vSphere 5you may recall a diagram about the levels of “Inception” that can be performed with nested ESXi. That is, the number of times you could nest ESXi and still have it be in a “functional” state. With vSphere 5.0, the limit that I was able to push was 2 levels of nested ESXi. With latest release of vSphere 5.1, I have been able to push that limit now to an extraordinary 3 levels of inception!

You might ask why would someone want to do this … well I don’t have a good answer other than … because I can? VHV is one of the coolest “unsupported” feature in my books and I’m glad it is working beyond what it was designed for.

For proper networking connectivity, also ensure that either your standard vSwitch or Distributed Virtual Switch has both promiscuous mode and forged transmit enabled either globally on the portgroup or distributed portgroup your nested ESXi hosts are connected to.

Nesting “Other” Hypervisors

For those of you who feel inclined to run other hypervisors such as Hyper-V, you can do so with latest release of ESXi 5.1. The process if very straight forward just like running nested ESXi host.

Step 1 – Create a Virtual Hardware 9 VM and select the appropriate guestOS. In this example, I selected Windows Server 2012 (64-bit) as the guestOS version.

Step 2 – Enable VHV under the CPU section if you wish to create and run nested 64-bit VMs under Hyper-V

Step 3 – You will need to add one additional .vmx parameter which tells the underlying guestOS (Hyper-V) that it is not running as a virtual guest which in fact it really is. The parameter is hypervisor.cpuid.v0 = FALSE