ESXi host(s) disconnect from vCenter due to network loop

Products

• VMware vSphere ESXi

Issue/Introduction

ESXi hosts may experience connectivity issues when there is a loop in the network.  They may become unreachable over the network, disconnecting from the vCenter, and inaccessible via SSH.

Environment

VMware vSphere ESXi

Cause

Several factors can contribute to this type of failure

VLAN Configuration Issues

• Network loops created by improper VLAN implementation
• Overlapping VLAN configurations
• Incorrect VLAN tagging
• Trunk configuration mismatches

Network Design Problems

• Spanning tree protocol issues
• Redundant paths without proper loop prevention
• Missing VLAN isolation
• Improper network segmentation

Implementation Errors

• Incorrect VLAN assignments
• Missing or incorrect trunk configurations
• Layer 2 domain conflicts
• Switch configuration mismatches

Resolution

Troubleshooting Steps

• Review recently implemented VLAN configurations
• Check for network loops using standard network tools
• Verify VLAN trunk configurations
• Examine spanning tree topology

Remediation Actions

• Temporarily disable suspect VLANs to isolate issues
• Verify service restoration after VLAN changes
• Document working configurations
• Implement corrected VLAN design if needed

Prevention Measures

• Implement change control for VLAN modifications
• Document successful VLAN configurations
• Create testing procedures for network changes
• Maintain network topology documentation
• Regular review of network design