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It can be frustrating to troubleshoot VMware Horizon environments, whether on-premises or cloud-hosted, because there are many steps IT professionals must take between the initiation of the session and the presentation of the virtual desktop.
As an IT admin, you should attempt to master the potentially tedious task of troubleshooting VMware Horizon desktops and all the steps involved in this process. Start by understanding the essential points of this VMware Horizon View troubleshooting guide, including how to initiate a troubleshooting session and the common issues to look for.
Initiate a VMware Horizon View troubleshoot session
Adhere to the following troubleshooting guide to establish a connection to a desktop on VMware Horizon:
- Prompt the end user to open up the Horizon client or HTML5 client.
- The user then authenticates through on the connection server and is potentially tunneled through the Unified Access Gateway (UAG) if he or she authenticates externally.
- Horizon will verify the entitlements for the user and present the entitlements to the client.
- The user should then open up a desktop in the pool.
- The Connection Server will verify if a desktop is already assigned to the user:
- If no assignment exists, the server will create a new assignment.
- The horizon client will receive a message to establish a connection to the assigned desktop.
- The client will attempt to connect to the desktop:
- In case the session is tunneled through the UAG, the UAG tries to establish the session instead.
- Once Horizon establishes the connection, the user is presented with a desktop.
- If you have configured the remoting protocol correctly and the network allows it, the user receives remoted display information on the horizon client.
- If an Nvidia Corp. virtual GPU (vGPU) profile is configured correctly, the user can run accelerated applications, and the video stream encoding is offloaded to the GPU
There may be some additional steps in this process if you have to choose different types of clones, set up some specific settings in the Connection Server -- with Cloud Pod Architecture or specific authentication settings -- or you have integrated Horizon with Workspace One. However, these steps work in most cases.
A VMware Horizon View troubleshooting guide to common desktop issues
The most common VMware Horizon issues that you will need to troubleshoot focus on authentication, connectivity and UX.
Users are unable to authenticate in my Horizon Client
The entitlement information is stored in a Lightweight Directory Access Protocol (LDAP) database that is synchronized between the connection servers, and sometimes the LDAP sync doesn't perform well. This is especially common for organizations with a giant Active Directory (AD). It's common for a user to receive authentication errors if there are connectivity issues between the Connection Servers as well. The first thing you should do is check if any sync issues exist. You can do so by executing the following command on any of the Connection Servers:
repadmin.exe /showrepl localhost:389 DC=vdi,DC=vmware,DC=int
The result will inform you about any issues that exist. Antivirus tools can also prevent users from authenticating on the Connection Servers. If you create a couple hundred new desktops that are set to receive new AD accounts, this can also cause authentication issues from Horizon. Some antivirus offerings consider these actions a distributed denial-of-service attack and block user access from the Connection Servers to the AD. Therefore, it's essential that you put the proper exclusions in place.
Users receive the error message that no desktop is available
This could occur due to one of several factors. The user may not have any entitlements to a desktop pool. In this case, you should check the entitlements. Another issue could be that the desktop pool has reached the limit of available desktops. You can increase the limit of desktops, assuming the user has the proper licensing, or log off disconnected sessions to free up virtual desktops.
If the user has an assigned desktop in a manual pool, it could mean the desktop is shut down and Horizon isn't able to power it on. In this case, you should always check the vSphere environment the desktop is hosted on to verify if enough cluster resources are available to boot the virtual desktop. Finally, you should check the agent status of the virtual desktop in the Connection Server, which will show the active status of the desktop.
Users click on the desktop but don't get a remoted session to the desktop
This could also mean a couple of things. If the session is tunneled, it could mean that the port is blocked by a firewall. If the user is presented with a black screen, that's most likely the reason.
Even if the authentication works, the blast protocol may be unable to access the virtual desktop when the Horizon Client tries to establish the session. In this scenario, check firewalls for port 443 and 8443 to ensure the traffic is configured correctly.
Another issue could be that the domain name server isn't configured correctly or has some issues in the data center. Check pointer records and A records to make sure name resolution is functioning properly. In case the user has an HTML5 client, you should try a different browser. Not all browsers can handle SSL traffic in the same way. In some cases, users aren't able to use Apple's Safari browser, but Google Chrome generally works fine.
Users are dealing with poor UX
Like the previous two scenarios in this VMware Horizon View troubleshooting guide, this issue could be caused by several different factors. Your first step should be to check if there is enough bandwidth for users' desktops and what the latency is between the endpoint and the virtual desktop. By running the Horizon Performance Tracker inside the virtual desktop, you can check the essential network performance metrics. If the latency exceeds 100 milliseconds, you may need to adjust the Blast Extreme settings to improve UX.
The easiest way to accomplish this is through Horizon Smart Policies in the VMware Dynamic Environment Manager (DEM). You should assign a different smart policy to the end user and let them refresh their DEM settings. Horizon will adjust the settings in real time, so it will directly affect the user's session.
Another common issue is related to Nvidia vGPU. If a vGPU profile is attached but no license is assigned, the maximum frame rate will be lowered to 3 frames per second. This will cause poor UX, so desktop admins should check if a license is assigned in the Nvidia vGPU Control Panel in the virtual desktop.