For desktops to be usable, they must register (that is, establish communication) with the correct controller or with any one of the controllers, if there are more than one.

The default operation, whose configuration is briefly described in this topic, uses information in the desktops’ registries to establish communication. This is referred to as registry-based controller discovery. You can also use an Organizational Unit (OU) in Active Directory (AD). This is referred to as AD-based controller discovery. If you use that discovery method, you must configure the GUID of the OU in the desktops’ registries.

Active Directory-Based Controller Discovery

To perform AD-based controller discovery, run the PowerShell script Set-ADControllerDiscovery.ps1 that is installed on each controller in the folder $Env:ProgramFiles\Citrix\Broker\Service\Setup Scripts.

The script must be run on a controller in the site by a user who is a full administrator of the controller and who has the appropriate permissions to make changes in the relevant OU in AD.

For more information about the script, see Active Directory Considerations.

Registry-Based Controller Discovery

If you change discovery methods, or add or move controllers, you must update the ListOfDDCs registry key on each virtual desktop. Alternatively, use a Group Policy Object to do this. The ListOfDDCs registry key is:

HKEY_LOCAL_MACHINE\Software\Citrix\VirtualDesktopAgent\ListOfDDCs (REG_SZ)

This key lists all of the controllers in the site (and is the equivalent of Active Directory’s XenDesktop site OU). For multiple controllers, the key’s value is a space-delimited list of FQDNs. If both ListOfDDCs and FarmGUID (HKEY_LOCAL_MACHINE\Citrix\VirtualDesktopAgent\FarmGUID) are present in the registry, the ListOfDDCs value is used for controller discovery. (FarmGUID will be present if a site OU was specified when the Virtual Desktop Agent was installed.)

Additionally, be aware of the ListOfSIDs registry key. Use this to avoid possible security threats from a compromised Domain Name System (DNS) server. The ListOfSIDs registry key is:

HKEY_LOCAL_MACHINE\Software\Citrix\VirtualDesktopAgent\ListOfSIDs (REG_SZ)

For more information, see http://support.citrix.com/article/ctx118976/.

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