Posted on April 7, 2016 · Posted in Misc

FAQ: KMS Activation of Microsoft Products

On webpages we have already discussed various aspects of configuration and operation of KMS (Key Management Service). Let’s try to collect the basic information and the necessary links about KMS activation technology in a single article.

KMS infrastructure consists of a KMS server to be activated in Microsoft (this operation is performed once online or by phone) and KMS clients, which send their activation requests to the KMS server. User and server Microsoft Oss  and MS Office can become KMS server clients.

KMS server is activated using a special corporate VLC key (KMS host key), which can be obtained by any Microsoft corporate customer on Microsoft Volume Licensing site ( KMS server is activated only once.

Microsoft KMS Activation Service architecture

The number of activations using KMS server is unlimited. It shall also be noted that the information about the activations and their amount is not transferred elsewhere outside the company.

A KMS server can activate clients in different domains, as well as clients in the workgroups.

When a KMS server is installed, a special SRV (_VLMCS) record is registered in DNS. Using this DNS record a client can find the name of the KMS server in the domain. To activate a KMS client, it has to possess a special public KMS key called a GVLK (Generic Volume License Key). After the GVLK is specified, the KMS client tries to find a SRV record correspondent to the KMS server in DNS and get activated.

Here is the list of universal KMS keys (GVLK) for the latest Microsoft products:

KMS Server Requirements

  1. Port 1688 must be opened between the client and the KMS server. When the KMS server is activated online (once), Microsoft websites have to be available on ports 80/443. In an isolated environment, the KMS server can be activated by phone.
  2. You can activate products using KMS server if the following requirements to the minimum number of KMS clients (so called activation threshold):
    • Client OSs: 25
    • Server OSs: 5
    • MS Office: 5

    Tip. If necessary, the activation counter on the KMS server can be increased using a script.

  3. Computers with products activated on the KMS server have to connect to the corporate network with the KMS server at least once in 180 days (the activation validity interval) to renew their activation. By default, KMS client computers attempt to renew their activation every seven days. If activation succeeds, activation validity interval reset to 180-day.
  4. KMS is not resource-consuming, so this role can be installed on any server. KMS doesn’t have to be highly available. If a KMS server is not available for several hours (or even days), the downtime will not affect the company in any way.

Activation of MS Office on a KMS Server

To activate MS Office products on a KMS server, Microsoft Office Volume License Pack has to be installed (its version differs depending on MS Office version).

After License Pack for MS Office is installed, a corporate KMS key (VLK) for Office has to be installed and KMS server for Office has to be activated.

Microsoft Office Volume License Pack

For more info on MS Office activation, see

Additional Tools

To manage KMS server and keys you can install a special tool: Volume Activation Management Tool (VAMT).

  • VAMT is not delivered as a part of the OS, it is included in Windows Assessment and Deployment Kit (ADK) and installed separately
  • .NET Framework is required for VAMT
  • As VAMT database, SQL Server Express is used
  • The latest available version, VAMT 3.1, is supported in all Misrosoft OSs including Windows 8.1 and Server 2012 R2


  1. KMS servers to activate Windows and Office products can run on single server running Windows Server.
  2. For users, who do not connect to the corporate network with the KMS server, it is recommended to use MAK (Multiple activation key).

Common Mistakes When Using a KMS Server

  • The installation of the corporate KMS host key (VLC) on the clients
  • GVLK key doesn’t correspond to the OS version on the host to be activated
  • The KMS server has to be updated to support activation of the latest Microsoft products (here, for example, the update procedure of the KMS server running Windows 2008 R2 to support activation of Windows1 and Windows Server 2012 R2 is described)
  • If the error 0xC004F074 appears during activation, the reason can be the absence of the SRV record in DNS. It can be created manually or the KMS server address can be specified (command shown below)
  • The error 0xC004F038 means that there are not enough systems for activation in your network (Activation Thresholds)

The Main Commands to Manage Activation on a KMS Client

Installation of a public KMS key on a client:

slmgr /ipk

Setting a KMS server and port:

slmgr /skms

OS activation on a KMS server:

slmgr /ato

Information about the status of OS activation:

slmgr /dlv

All licensing information (including MS Office activation status):

slmgr /dlv all

Tip. A pop-up window with licensing information is not always scrollable and doesn’t often fit in the screen. You can display this information as a text file to make the analysis more convenient:

cscript.exe c:\windows\system32\slmgr.vbs /dlv all > c:\tmp\dlv.txt

Tip. As an extension of KMS technology, another type of MS products activation should be mentioned — Active Directory Based Activation (ADBA). ADBA allows to automatically activate clients running Windows 8, Windows Server 2012 and MS Office 2013 included in the domain. In this case, there is no dedicated KMS server, and the activation is performed by the Active Directory extension.

If you have any questions concerning Microsoft KMS activation, you are welcome to ask them in the comments and I’ll try to answer them.

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