How to use Microsoft KMS server 2016 to activate a Windows Server 2008 R2

We are busy building a new environment. Most of our servers are Windows server 2016. And so is our KMS server.

To run some old applications, we need to activate a few Windows Server 2008 R2 operating systems (Via Citrix PVS).

When I add the Windows Server 2008 R2 KMS key to the Windows Server 2016 KMS server I get this error message;

Error: 0xC004F050 The Software Licensing Service reported that the product key is invalid.

We successfully added Windows Server 2016 KMS keys to the KMS server

Questions;

1. Is it possible to activate Windows Server 2008 via a 2016 KMS server
2. Why is our product key failing?

A Windows Server KMS key allow to to activate any older version of Windows Server.

So, since you added Windows Server 2016 KMS keys to the KMS server, you have nothing special to do, your Windows Server 2008 should active just fine, provide you reached the activation threshold (5 servers IIRC).

Note : this is not true for Office.