Fixed: VMware Horizon UAG "Unrecognized Request Detected" Warning

Fixed: VMware Horizon UAG "Unrecognized Request Detected" Warning Horizon UAG: Solving the 'Unrecognized Request Detected' Mystery Published: May 5, 2026 | Category: VDI Infrastructure & Security Overview of the Symptom In a VMware Horizon environment, administrators often encounter a yellow warning on the Unified Access Gateway (UAG) stating: "Unrecognized request detected." Curiously, the Connection Server remains healthy (Green), and the event often vanishes from the Horizon Console after a few minutes. 1. Root Cause Analysis This alert is a result of the UAG’s built-in security filtering. It triggers when the UAG receives traffic that does not conform to the expected Horizon protocol or HTTP standards. External Bot Scanning: As an edge device, the UAG is frequently hit by automated scanners (e....
Post a Comment

Zero Client (Teradici 23.01) Cannot Connect to Horizon View via VIP — The Real Cause Wasn't What AI Told Me

Zero Client (Teradici 23.01) Cannot Connect to Horizon View via VIP — The Real Cause Wasn’t What AI Told Me

Environment:
∙ VMware Horizon View 2512
∙ Teradici / HP Anyware Zero Client firmware 23.01
∙ Multiple Horizon Connection Servers behind NSX Load Balancer (VIP)

Symptom
Teradici Zero Client firmware 23.01 failed to connect to the Horizon View Connection Server via VIP address. FQDN access also failed.
Notably:
∙ Older Teradici firmware versions connected without issues
∙ VMware Horizon Client (software) on the same network connected without issues
∙ Only the 23.01 Zero Client against the VIP was failing

What AI Said
I asked Gemini to analyze the issue. The response was detailed and logically structured — it pointed to:
∙ SSL/TLS certificate validation tightening in 23.01
∙ Cipher suite mismatches between NSX and the new firmware
∙ PCoIP session persistence issues on the load balancer
∙ Possible firmware bugs in the 23.01 transition build
The analysis was technically plausible. Gemini even said:
“The probability that this is a security enforcement issue rather than a functional defect is over 90%.”
It was a convincing answer. It was also wrong.

The Real Cause
After spending time chasing certificate and TLS configurations, I went back to basics.
I tested each Connection Server individually — bypassing the VIP.
Result: one Connection Server was down.
The actual cause:
NSX was not properly detecting the unhealthy Connection Server and continued routing traffic to it. The 23.01 Zero Client happened to be load-balanced onto the failed node consistently enough to appear as a firmware compatibility issue.
Older firmware versions and software clients were connecting successfully — not because they were more compatible, but because they were being routed to the healthy servers.

Why AI Got It Wrong
AI analyzed the symptom pattern (version-specific failure) and generated the most statistically likely explanation. That’s version incompatibility or security enforcement change.
What AI cannot do: check your actual infrastructure. It had no visibility into the health state of your individual Connection Servers or your NSX load balancer behavior.
The lesson: when AI gives a version-specific explanation, always rule out infrastructure-level failures first.

Resolution
1. Identified the failed Connection Server via individual IP access test
2. Investigated and restored the problematic Connection Server
3. Reviewed NSX health check configuration — the monitor was not correctly detecting the node failure
4. Temporary fix: pointed the affected Zero Client directly to a healthy Connection Server IP

Checklist for the Same Symptom
If you see a specific Zero Client version failing on VIP while other clients succeed:
∙ Test each Connection Server individually (bypass VIP)
∙ Check NSX / load balancer health monitor logs
∙ Confirm which node the failing client is being routed to
∙ Do not assume firmware incompatibility until infrastructure health is confirmed

Key Takeaway
AI diagnosis is a starting point, not a conclusion.
When version-specific symptoms appear in a load-balanced environment, check your infrastructure health before chasing firmware or certificate issues.


14+ years of VDI operations. Writing about the cases where the obvious answer was wrong.



Comments

Post a Comment

Popular posts from this blog

Troubleshooting VMware Horizon Client vdpConnect_Failure Issue

  Introduction VMware Horizon Client is a widely used solution for virtual desktop infrastructure (VDI). However, users may encounter various connection issues, one of which is the vdpConnect_Failure error. This error often results in a black screen followed by a disconnection, preventing users from accessing their virtual desktop. In this article, we will explore the possible causes of this issue and provide step-by-step solutions to resolve it. Common Causes of vdpConnect_Failure 1. RPC Server Unavailable One of the most common reasons for vdpConnect_Failure is the unavailability of the Remote Procedure Call (RPC) server . This can occur due to: The RPC service being stopped or disabled Network issues preventing communication with the server Firewall blocking required ports 2. Display Protocol Issues (Blast/PCoIP/RDP) Horizon Client uses different display protocols such as Blast, PCoIP, or RDP . If there are misconfigurations or compatibility issues with the selected protocol, ...
Read more

VMware Horizon Agent “Protocol Error” — Fixed by Windows Firewall Configuration

  🖥️ VMware Horizon Agent “Protocol Error” — Fixed by Windows Firewall Configuration Overview Recently, I encountered an issue where several Horizon Agent–based virtual desktops in our environment showed the status “Starting other services” or “Protocol Error” in the Horizon Administrator console. Even after reinstalling the Agent (version 2206 ), the problem persisted. Symptoms Horizon Agent status: “Starting other services” → “Protocol error” Horizon main services appeared to be running normally Event Viewer showed Event ID 7000 for services such as: PASVC – failed to start LUFAV – not installed Reinstalling the Agent (even using Repair mode ) did not solve the issue Root Cause After deeper inspection, we discovered that on the affected VMs: Windows Defender Firewall (Domain Profile) → “Block all incoming connections, including those in the list of allowed apps” was checked (enabled). This setting silently blocks all inbound traffic , ev...
Read more

VMware / Omnissa Horizon Agent Unreachable – Causes and Fixes (Complete Troubleshooting Guide)

  Keywords: VMware Horizon Agent Unreachable, Omnissa Horizon Agent unreachable, Horizon View troubleshooting, Blast service issue, Horizon Agent not responding, VDI connectivity problem In VMware Horizon (now branded as Omnissa Horizon ), administrators frequently encounter the “Agent Unreachable” state in the Horizon Console. While a simple reboot often resolves the issue, persistent cases indicate deeper infrastructure, service, or network-layer problems. This guide provides a structured root-cause analysis and remediation checklist suitable for production VDI environments. What Does “Agent Unreachable” Mean? When a desktop shows Agent Unreachable , the Horizon Agent inside the VM cannot communicate with the Connection Server . The failure typically occurs in one of these control paths: Horizon Agent → Horizon Connection Server Blast Secure Gateway (BSG) → Agent Windows OS services → Horizon Agent service Firewall or network layer blocking agent heartbeat ...
Read more