Cannot add vCenter Server to HCX Manager: "Failed to initialize connection to vSphere server" due to Proxy Configuration

Products

• VMware HCX

Issue/Introduction

When attempting to register or pair a vCenter Server with VMware HCX Manager, the connection may fail even if DNS and basic network connectivity are functional. This issue typically occurs during the site-pairing phase or initial configuration when an active proxy configuration intercepts traffic destined for the local vCenter. This article provides the steps to identify and bypass or remove the proxy configuration to restore communication between the appliances.

Symptoms:

• Unable to register or add a vCenter Server to the VMware HCX Manager.
• When attempting to add the vCenter Server via the HCX UI, encounter the following error: "Error: VCenter https://<vcenterfqdn> is not reachable. Failed to initialize connection to vSphere server <vcenterfqdn>"
• A red indicator may appear next to a previously paired vCenter Server showing that the connection is not okay.
• Basic network connectivity tests, such as DNS resolution (nslookup) and ICMP (ping), from the HCX Manager appliance to the vCenter Server are successful.
• The vCenter administrator credentials used for the integration are valid and work when logging directly into the vSphere Client.

Environment

• VMware HCX
• VMware vCenter Server

Cause

This issue occurs when a proxy server is configured in the HCX Appliance Management Interface (VAMI on port 9443) that unintentionally intercepts, routes, or blocks the internal traffic intended for the local vCenter Server. If the vCenter Server is not explicitly bypassed in the proxy settings, the HCX Manager will attempt to reach the vCenter Server through the proxy, leading to connection failures.

Resolution

To resolve this issue, remove the proxy configuration (or configure a proper proxy bypass/exception for the vCenter Server) and restart the relevant HCX services.

Resolution:

Note: Ensure that no active migrations are in progress before applying this workaround. Restarting the services during this procedure will cause ongoing migrations to fail.

1. Log in to the HCX Appliance Management UI using a web browser: https://<HCX-Manager-IP-or-FQDN>:9443 using the admin credentials.
2. Navigate to the Proxy configuration settings.
3. Delete the existing proxy configuration. (Note: If a proxy is required for other HCX outbound communications, ensure that the vCenter Server FQDN and IP address are added to the proxy exclusion/bypass list instead of deleting the proxy entirely).
4. Save the configuration changes.
5. Stop and Start the HCX Application and Web services to apply the changes. This can typically be done from the appliance management interface or via the HCX appliance CLI:
   1. Stop Migration Planning first
   2. Then stop app-engine and web-engine services.
   3. Then start app-engine and web-engine services.
6. Once the services have successfully restarted, log back into the standard HCX Manager UI (port 9443).
7. Attempt to add or register the vCenter Server again. The connection should now initialize successfully.

Additional Information

Configure a Proxy Server