NSX Load Balancer Service Monitor Failure - Pool Members Unresponsive

Products

• VMware NSX

Issue/Introduction

• VMware NSX Load Balancer identifies backend application/service pool members as unresponsive. A service monitor failure is observed during health check communication on TCP port. Simultaneous packet captures performed from the Edge to the server pool, and from the server pool back to the load balancer to observe traffic flow during the monitor check verify this behavior.
• Packet capture analysis confirms the NSX Load Balancer is actively sending monitor probes to the server pool. A grep for expected HTTP traffic destined for IP returns no application response.

Environment

VMWARE NSX 

Cause

An application-layer or guest OS-level failure within the service pool member is causing the backend application to fail to return a response or expected HTTP traffic to the load balancer's monitor probes. Packet captures prove that the load balancer is successfully transmitting probes and they are reaching the destination, confirming the NSX routing and load balancing configuration is operating as expected.

Resolution

 

• Investigate the backend server pool members  to determine why the application is not responding on TCP port .

• Verify Listener State: Confirm the application service is actively bound and listening on TCP port .

• Review Guest OS Firewall: Check local firewall rules (e.g., iptables, Windows Firewall) for dropped or blocked traffic on port  from the Load Balancer IP.

 

 

Additional Information

• Troubleshooting NSX using Packet Captures
• NSX Native Load Balancer Pool Members Down Due to Pool members Unresponsive to Health Monitors