Configuring KMS Clients

This section describes concepts for installing and configuring computers as KMS clients. By default, Volume License editions of Windows Vista, Windows 7, Windows Server 2008, and Windows Server 2008 R2 are KMS clients. If the computers the organization wants to activate by using KMS are using either of these operating systems and the network allows DNS auto-discovery, no further configuration is needed.

If a KMS client is configured to search for a KMS host using DNS but does not receive SRV records from DNS, Windows 7 and Windows Server 2008 R2 log the error in the event log.

Manually Specifying a KMS Host

Administrators can manually assign a KMS host to KMS clients by using KMS host caching. Manually assigning a KMS host disables auto-discovery of KMS on the KMS client. A KMS host is manually assigned to a KMS client by running:

slmgr.vbs /skms <value>:<port>

where value is either the KMS_FQDN, IPv4Address, or NetbiosName of the KMS host and port is TCP port on the KMS host.

Enable Auto-discovery for a KMS Client

By default, KMS clients automatically attempt to discover KMS hosts. Auto-discovery can be disabled by manually assigning a KMS host to a KMS client. This action also clears the KMS host name from the KMS client’s cache. If auto-discovery is disabled, it can be re-enable by running slmgr.vbs /ckms at a command prompt.

Adding Suffixed Entries to KMS Clients

By adding the address of a DNS server containing the SRV RR as a suffixed entry on KMS clients, administrators can advertise KMS hosts on one DNS server and allow KMS clients with other primary DNS servers to find it. For more information about configuring a domain suffix search list on KMS clients, see the Microsoft Help and Support article, “How to configure a domain suffix search list on the Domain Name System clients,” at

Deploy KMS Clients

The information in this section is for Volume Licensing customers using the Windows Automated Installation Kit (Windows AIK) to deploy and activate a Windows operating system. Prepare KMS clients for deployment by using the System Preparation Tool (Sysprep) or the Slmgr.vbs script:

  • Sysprep. Before capturing an image, run Sysprep with the /generalize command-line option to reset the activation timer, security identifier (SID), and other important settings. Resetting the activation timer prevents the image’s grace period from expiring before the image is deployed. Running Sysprep.exe does not remove the installed product key, and administrators are not prompted for a new key during mini-setup. If no rearms are left, the Sysprep operation completes but the activation timers are not changed and an error is returned that explains the situation.

  • Slmgr.vbs. When building demo virtual machines (VMs) for internal use (e.g., building VMs for the organization’s sales department or to set up a temporary training environment), running the Slmgr.vbs script with the /rearm command-line option extends the grace period another 30 days, which in turn resets the activation timer but makes no other changes to the computer. The activation timer can be reset three times for computers running Windows 7 or Windows Server 2008 R2.

Manually Activate a KMS Client

By default, KMS clients automatically attempt to activate themselves at preset intervals. To manually activate KMS clients (for example, disconnected clients) before distributing them to users, use the Control Panel System item, or run slmgr.vbs /ato at an elevated command prompt. The Slmgr.vbs script reports activation success or failure and provides a result code. To perform activation, the KMS client must have access to a KMS host on the organization’s network.

Converting MAK Clients to KMS and KMS Clients to MAK

By default, Windows 7 and Windows Server 2008 R2 operating systems use KMS for activation. To change existing KMS clients to MAK clients, simply install a MAK key. Similarly, to change MAK clients to KMS clients, run:

slmgr.vbs /ipk <KmsSetupKey>

where KmsSetupKey is one of the setup keys shown in Table 4. After installing the KMS setup key, activate the KMS client by running cscript slmgr.vbs /ato.

Table 4   KMS Client Setup Keys

Operating System Edition

Product Key

Windows 7


Windows 7 Professional


Windows 7 Professional N


Windows 7 Enterprise


Windows 7 Enterprise N


Windows 7 Enterprise E


Windows Server 2008 R2


Windows Server 2008 R2 HPC Edition


Windows Server 2008 R2 Datacenter


Windows Server 2008 R2 Enterprise


Windows Server 2008 R2 for Itanium-Based Systems


Windows Server 2008 R2 Standard


Windows Web Server 2008 R2


Converting Retail Editions to Volume Activation

Retail editions of Windows 7 Professional and Windows Server 2008 R2 can be converted to KMS clients, provided that the organization has acquired the appropriate volume licenses and conforms to the Product Use Rights. To convert Windows 7 Professional and all editions of Windows Server 2008 R2 from retail to a KMS client, skip the Product Key page during operating system installation. When installation is complete, open an elevated Command Prompt window and type:

Slmgr.vbs /ipk <SetupKey>

where SetupKey is the KMS client setup key from Table 4 that corresponds to the edition of Windows 7 or Windows Server 2008 R2.