Troubleshooting HCX Interconnect and Network Extension Issues Due to VLAN Network Loops

Products

• VMware Cloud on AWS
• VMware HCX

Issue/Introduction

HCX environments may experience connectivity issues affecting interconnects and network extensions, including

• Network extension tunnels showing as down
• Failed diagnostic tests
• Loss of communication with extended VMs
• IX connections failing
• Cross-site connectivity disruptions
• Unexplained tunnel status changes after network modifications

Common symptoms include:

• Multiple service mesh connections showing down status
• Diagnostic errors in HCX interface
• VM communication failures across extended networks
• Issues affecting multiple sites simultaneously
• Problems emerging after VLAN configuration changes

Environment

• VMware HCX
• VLANs for HCX traffic

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

Initial Assessment

• Document all affected service mesh connections
• Identify patterns in failed connections
• Review recent network changes
• Map affected sites and connections

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

Additional Information

Best Practices

• Always verify VLAN configurations before implementation
• Test network changes in isolated environments when possible
• Maintain detailed documentation of network topology
• Implement proper change control procedures

Note: When implementing new VLANs in an HCX environment, careful consideration should be given to existing network topology and potential impact on service mesh connections. Always follow proper network design principles to prevent loops and other network issues.