Citrix Xendesktop relies on a VDA, or virtual desktop agent to maintain communication with every virtualized desktop in the environment, and the associated desktop controller. One of the most common calls you may get regarding Xendesktop might be that your virtual desktop agent is not reporting in, or is not appearing in the administration console on the Citrix DDC. In this article, we’ll discuss how to troubleshoot this condition, explain why it happens, and hopefully give you some good resolutions to try!
What are some reasons this might occur?
- A network problem may be preventing the virtualized desktops from having a valid routable path to the Xendesktop DDC
- A firewall could be installed or misconfigured on the virtualized desktop, causing network communicating from the VDA to the DDC to be blocked.
- DNS may be misconfigured, or not working properly, causing your packets to go nowhere.
- If Kerberos is in use, it could be the result of improper time synchronization between the virtualized desktops and DDC.
- Faulty domain membership can cause this issue if a DDC or virtualized desktop has its domain membership corrupted or otherwise misconfigured.
- Problems with Windows WCF can cause this issue when active directory does not have the correct information for a server’s Service Principal Names (SPNs).
- Use of multiple network adapters on virtualized desktops can mess with the security negotiation, and cause issues. This is a known problem.
- GPOS and local security policy settings can cause VDA reporting to fail. You will see this usually with the case of large financial clients, or high security clients such as government and military branches.
- VDA software corruption can cause the VDA to fail, or otherwise not report in.
How do I troubleshoot these problems?
-Download and install the XDPing tool, available from Citrix (CTX123278), and it will check network connections and give you a lot of data to work with.
- Disable any personal firewall software that may be installed on virtualized desktops, and test to verify it the VDA can now report in to the DDC. If the problem goes away during this test, you’ll know you need to fine tune your firewall configuration on the virtualized desktop.
- Verify DNS is working properly by pinging the DDC from the virtualized desktop, and visa versa. Both server and virtualized desktop should be able to ping each other by DNS name without issue. If you find that you can only ping by IP address, or fully qualified name, etc — Check into your DNS configuration for the source of the problem.
- If Kerberos is in use, make sure that the time is set to be the same on both the virtualized desktop, and the Citrix DDC. If they are out of synch, it can cause security headers on packets to think they have timed out, and force an erroneous rejection.
- Verify that both virtualized desktop and Citrix DDC are members of the domain. If DDC can successfully connect to other VDA’s, then this will usually rule domain problems out with the DDC. If that is the case, focus on the VDA and consider switching it to a workgroup, then switching it back to a domain in order to force domain membership overwriting.
- Consider using the active directory explorer tool to verify Service Principal Names (SPNs) are correct for your DDC. If there is active directory corruption on the computer account, or anywhere else — it could cause VDA’s to not be able to report in.
- Disable all network adapters on the virtualized desktop except for one, and test with each to see if the issue goes away.
- Reset local security policy to defaults, and as always with Citrix GPO issues — test the DDC after adding it to a virgin OU with inheritance blocked. If the problems dissapear after taking these steps, you know you had a permissions issue.
- Uninstall and Reinstall the Citrix VDA software from the virtualized desktop in order to repair any corruption that may exist.
For an example of how to run XDPing, and some of the errors you might encounter, watch this quick video: