How many VMs can you run in Hyper-V before you need to buy a license?

When running virtual machines (VMs) in Microsoft Hyper-V, you can run up to two VMs on the host machine without needing to purchase any additional licensing from Microsoft. This is because Windows includes Hyper-V at no additional charge, and the license terms allow you to run up to two VMs on the host. However, there are some caveats to be aware of.

Windows Versions that Include Hyper-V

Hyper-V is included in certain versions of Windows at no extra cost. Here are the specifics:

  • Windows 10 Pro and Enterprise – Hyper-V is included in these versions.
  • Windows 8.1 Pro and Enterprise – Hyper-V is included in these versions.
  • Windows Server – All editions of Windows Server include Hyper-V.

So as long as you are running Windows 10 Pro/Enterprise or Windows 8.1 Pro/Enterprise on the host machine, you can use Hyper-V without needing to buy the standalone Hyper-V Server product. Windows Server licenses also include unlimited Hyper-V use.

The 2 VM Limit

The basic licensing rule is that you can run up to two VMs on top of the host Windows machine without needing to buy additional licenses. This is stated in Microsoft’s licensing documents:

For software editions that include Hyper-V technology, customers may run up to two instances of the software in VMs on a properly licensed server without having to license those VMs. Additional software licenses are required to run more than two VMs.

So for example, if you are running Windows 10 Pro as the host OS, you can run up to two Windows 10 VMs on top of it without needing more licenses. The two VM limit applies no matter how powerful the host computer is. However, there are important caveats…

Licensed for the Host Counts Too

An important point is that the base OS license for the physical host machine counts as one of your two allowed VM licenses. For example:

  • If you are running Windows 10 Pro on the physical host, this counts as 1 license.
  • You can run 1 additional Windows 10 Pro VM on this host.
  • A total of 2 Windows 10 licenses are accounted for (Host OS + 1 VM).

So you cannot run the Windows 10 Pro host OS and then spin up 2 Windows 10 Pro VMs on that host. The host OS license counts as one of the two allowed instances.

VM Licenses Must Match Host OS

The second big caveat is that the VM licenses must match the base OS license on the host. For example:

  • If the host is running Windows Server 2016 Datacenter, you can only run Windows Server 2016 VMs.
  • You cannot run mixes of Windows 10 and Windows Server VMs if the host is licensed for Windows Server.

Microsoft does not allow you to mix and match client and server OSes when licensing VMs. The VM licenses must match the underlying host license.

What About Linux VMs?

Can you run Linux VMs on top of Windows without needing additional licenses? The answer is yes!

Microsoft allows you to run Linux distributions or other non-Windows VMs on top of Windows without needing to buy any additional licenses. These Linux/other VMs do not count towards the 2 instance limit.

For example, if your host is Windows Server 2016, you could run:

  • Windows Server 2016 (1 license)
  • Windows Server 2016 (2nd license)
  • Ubuntu Server
  • CentOS

The two Windows Server VMs take up the included licenses. But Ubuntu and CentOS don’t require licenses, so you can run as many of those VMs as you want.

What About Running Windows Client as VMs?

Can you run Windows client OSes like Windows 10 Pro as VMs on top of Windows Server? The short answer is no. Microsoft specifically prohibits this. You can only run server OS editions in VMs when the host is a Windows Server OS.

For example, if your host is Windows Server 2022, you could not legally run:

  • Windows Server 2022
  • Windows Server 2022
  • Windows 10 Pro

The Windows 10 Pro VM would not comply with the licensing terms here. You can only run server VMs on server hosts per Microsoft’s rules.

Non-Production Use Rights

Microsoft does grant some flexibility for non-production uses. If you are just testing or doing development/evaluation, you can actually run Windows client VMs on server hosts without needing new licenses.

For example, you could legally do this for non-production uses:

  • Windows Server 2022 host
  • Windows Server 2022 VM
  • Windows Server 2022 VM
  • Windows 10 Pro VM (for testing)
  • Windows 11 Pro VM (for development)

So if you want to evaluate Windows 11 or spin up client VMs for testing purposes, this is allowed under the non-production use rights that Microsoft grants.

Running More Than 2 Windows VMs

If you need to run more than 2 virtualized Windows instances on a host, you will need to purchase additional licenses. Generally, you would buy Windows Server CALs (Client Access Licenses) to cover the extra VMs. Here are some examples:

  • Host is Windows Server 2022 Datacenter. You can run 2 Windows Server 2022 VMs under the host license.
  • If you need 5 more Windows Server VMs, buy 5 Windows Server 2022 CALs to license them.
  • Or if you need general CALs, buy 5 Windows Server Standard CALs to cover additional Windows Server/client VMs.

Without purchasing additional licenses, you are limited to just 2 Windows VMs before going out of compliance. CALs give you the required additional licenses.

External Connections

One other scenario requires additional licensing. If people external to your organization will be accessing the Windows VMs (like over a public internet connection), then you need Windows Server External Connector licenses for this:

If external users will access a server software VM (e.g., external users accessing a server running in a datacenter), each such “access” requires an External Connector license in addition to the software license assigned to the VM.

So if only internal users will connect to your Windows VMs, the included licenses cover it. But external user connections require External Connector licenses.

Summary of Key Points

Here are the key takeaways around licensing Windows VMs on Hyper-V:

  • Hyper-V is included with Windows 10 Pro/Enterprise and Windows Server.
  • You can run up to 2 VMs on these hosts without additional licenses.
  • The host’s base OS license counts as one of the two allowed instances.
  • VM licensing must match the host OS licensing.
  • No licensing required for Linux or non-Windows VMs.
  • Client OSes like Windows 10 can only run for non-production uses.
  • Buy additional Windows Server CALs to license more than 2 Windows VMs.
  • External connections require External Connector licenses.

As long as you are aware of these rules, you can maximize the use of Hyper-V’s included capabilities and only buy additional licenses when truly needed.

Frequently Asked Questions

Can I run unlimited Windows VMs with a Windows Server host license?

No, the included host server license only allows up to 2 Windows VMs to be run. You need to purchase additional CALs to license any Windows VMs beyond the first 2.

What if my host machine has lots of CPUs and RAM? Can I run more than 2 VMs?

No, the 2 instance limit applies no matter how powerful your host computer is. The number of licenses takes priority over hardware resources.

Can I run a mix of Windows Server 2016, 2019, and 2022 VMs on a Windows Server 2022 host?

Yes, you can mix and match versions as long as they are server editions. You cannot mix client and server SKUs.

Is there any way to run Windows 10 Pro VMs on my Windows Server host?

The only supported way is to use the non-production use rights for testing/dev purposes. Regular production use requires server VMs on a server host OS.

If I only run Linux VMs, do I need any licenses at all?

Nope! You can run unlimited Linux VMs on Windows without requiring additional licenses from Microsoft.

What if I want to run a mix of Windows and Linux VMs?

The Windows VMs will count towards the 2 instance limit as normal. No licensing needed for the Linux VMs.

Conclusion

In summary, Hyper-V provides an extremely cost-effective virtualization solution. You can leverage the built-in capabilities of Windows to run a robust Hyper-V environment without large licensing costs. Just be aware of the “two Windows VM” rule and when you will need to purchase additional CALs. Plan your VM deployments wisely and you can maximize value from Hyper-V’s virtualization benefits.

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