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VDAs for legacy OSes

As of 27th April 2026.

Tested successfully with Desktop Delivery Controller version 2507 LTSR CU1 and License Activation Service enabled on License Server 11.17.2.0 build 54100:

• Windows Server 2008R2 - VDA 7.15 CU9 (7.15.9000) download
• Windows 7 - VDA 7.15 CU9 (7.15.9000) download
• Windows Server 2012R2 - VDA 1912 CU10 download

Will not register:

• Windows XP SP3 32-bit - VDA 5.6 with 5.6.500 hotfix rollup

Further testing with Windows XP

Using Desktop Delivery Controller 7.15 CU9 (last version that allegedly supports VDA 5.6) on Server 2016 (last version that supports 7.15):

• Desktop Delivery Controller cannot connect to newer licence server required for License Activation Service (11.17.2.0 build 54100 from 2507 LTSR CU1) due to TLS v1.1 being disabled on licence server
  • Attempting to enable TLS v1.1 on licence server by adjusting SSLProtocols in C:\Program Files (x86)\Citrix\Licensing\WebServicesForLicensing\Apache\conf\extra\httpd-ssl.conf not successful, nor by enabling TLS v1.1 in HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols)
  • Can be tested with Get-LicCertificate -AdminAddress "https://licence.server:8083"
  • Setting up a NetScaler LB vServer on an internal IP address for SSL on port 8083 and TLS on 27000 that forwards to the backend licence server does allow connection, but no licences are found (as LAS licences aren't understood) - see below for how to set this up
  • Can install and connect to Citrix License Server version that came with 7.15 CU9, but as it doesn't support LAS, this just enables trial licensing
  • i.e. only 30-day trial licensing can be used
• Need to Set-BrokerCatalog -Name "<Machine Catalog>" -MinimumFunctionalLevel "L5" to support VDA 5.6 (default is 7.9 and newer)
• VDA reports its version and the OS version correctly to the DDC (can be seen in Studio), but registration fails. Event Viewer shows:
  • Exception 'Fail worker callback using SPN HOST/machine.domain.internal and IP address a.b.c.d' of type 'System.ServiceModel.FaultException' [Citrix.cds.Protocol.Controller.Fault]
• (VDA registration failure likely cause) Windows XP SP3 32-bit fully updated with Legacy Update is able to join domain with Server 2019+ domain controllers with a Windows Server 2008 R2 functional level and users can login, but Event Viewer shows:
  • Event ID 1097 : Windows cannot find the machine account. The Local Security Authority cannot be contacted
  • Event ID 1030: Windows cannot query for the list of Group Policy Objects
• Windows XP SP3 will run XenServer 7.1 with the XenServer 6.5 tools. The virtual machine will crash on newer version of XenServer if the 6.5 tools are installed. The OS can be installed on XenServer 8.4 if no tools are installed, but the Cirrus Logic 5446 Compatible Graphics Adapter will show windows with black backgrounds. Disabling the display adaptor or setting platform:vga=std on the VM in XenServer will work, but if the VDA is installed the Citrix Systems Inc. Display Driver will be added which will be used as the primary display at only 640x480 in 16 colours)

NetScaler commands to provide TLS v1.1 access to licence server

Replace:

• <LISTEN.IP> with the IP address to listen for incoming licence requests on
• <BACKEND.IP> with the IP address of the actual licence server
• <CERTKEYNAME> with a valid cert/key pair defined elsewhere