HCX IX Appliance Flapping and Thumbprint Exchange Failed Due To High Uplink Utilization - VMware HCX

Products

• VMware HCX

Issue/Introduction

Symptoms:

• VMware HCX IX appliances are constantly flapping and entering a critical state.

• The vSphere Client HCX plugin displays the following critical alert: "Thumbprint exchange with HBR server on appliance failed"
• No proxy configured
• The HCX Manager system logs reveal a timeout when attempting to reach the IX appliance: 

        com.vmware.vchs.hybridity.adapters.hbr.fault.HbrConnectionException: Error connecting to HBR server <server-ip>:8123. Reason: ConnectTimeoutException

• This symptom is predominantly observed during periods of high network utilization, such as weekend backup windows or heavy replication schedules.

Environment

VMware HCX 4.11.4

Cause

Extreme high utilization on the network uplinks causes packet drops and a network-layer timeout on TCP Port 8123. This completely blocks the HCX Manager from establishing a mandatory control-plane connection to the IX Appliance to complete the secure SSL thumbprint exchange.

Resolution

1. Log in to the vSphere Client and navigate to the ESXi host where the HCX Manager and IX appliances reside.

2. Monitor the Advanced Performance charts for Network utilization to confirm if uplink traffic is reaching maximum capacity during the times of the flapping alerts.

3. Identify and reschedule competing heavy network workloads (such as backup jobs) to avoid overlapping with critical HCX operations.

4. Implement Network I/O Control (NIOC) or physical switch Quality of Service (QoS) policies to prioritize HCX management traffic over standard VM traffic.

5. As an immediate mitigation step, migrate the IX appliance to the same ESXi host as the HCX Manager VM to ensure transit does not traverse the congested physical uplinks.