Guidance on installing a second KMS host for Office in an environment that has an existing KMS host for Windows.

Volume license editions Office 2010 support KMS activation. If your environment has an existing KMS host for activating Windows you have a few ways of activating Office 2010 using a KMS host:

  1. Use your existing Windows KMS host and add Office KMS support to it, if it is running a supported version of Windows (recommended)
  2. Migrate your Windows KMS host to a version of Windows that supports Office KMS and add Office KMS support to it (recommended)
  3. Install Office KMS support on a different computer and configure your environment for it.

Adding Office KMS support to an existing Windows KMS host if your best option, because doing so does not require any work being done outside of installing Office 2010 KeyManagementServiceHost.exe and installing/activating your Office 2010 KMS host key. The catch here is you must be running Windows KMS on an operating system that supports Office 2010 KMS. See this post for details on supported operating systems and for steps on installing Office 2010 KMS host:

I’m going to focus on option 3 for the rest of this post – installing Office KMS support on a second computer in an environment that already has a Windows KMS host running. The steps to install Office KMS is the same as step 1 and 2. So is installing and activating your key. You should note that this is not the recommended way of adding Office KMS support. Microsoft recommends only having a single KMS host for both Windows and Office. Having more than one KMS host on your network is not necessary and adds extra administration work to implement. The extra work involves preparing DNS to allow multiple computers to manage _VLMCS records.

When you install a KMS host and install a key, your KMS host registers itself in DNS by adding a _VLMCS record to DNS. The first KMS server to do this owns all rights for _VLMCS records. When you bring a second KMS host online it will not be able to register itself in DNS. Your KMS host will work, but your client computers will not be able to find it because the _VLMCS record for it does not exist in DNS. There are two way to fix this:

  1. Manually add a _VLMCS record to DNS for the second KMS host
  2. Create a global security group that contains the machine accounts for your KMS hosts and grant that group control over _VLMCS records in DNS (recommended).

You can follow the steps in this article to configure DNS for multiple KMS hosts: Keep in mind that the SRV resource record you want to edit permissions on in DNS is the _VLMCS record of your KMS host. Editing this record’s permissions to grant the global security control will enable additional _VLMCS records to be created by the other KMS hosts as needed.

We recommend the 2nd option here to keep future administrative tasks to a minimum. If you ever change the host name DNS will be updated automatically. Stale _VLMCS records in DNS can cause long delays in launching Office applications if they are requesting activation.

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