Troubleshooting Mass ESXi Host "Not Responding" States in vSphere 7.0 Environments

Products

• VMware vCenter Server

Issue/Introduction

This article provides guidance on troubleshooting scenarios where multiple ESXi hosts simultaneously enter a "Not Responding" state in vCenter Server. Such events can occur due to various reasons, including network outages, storage issues, or vCenter Server problems. Understanding the root cause is crucial for implementing effective solutions and preventing future occurrences.

Environment

- VMware vSphere 7.0 and later
- vCenter Server 7.0 and later
- ESXi 7.0 and later

Cause

Mass ESXi host "Not Responding" states can be triggered by several factors:
1. Network outages or disruptions
2. Storage array failures
3. DNS resolution issues
4. Time synchronization problems
5. vCenter Server malfunctions
6. Issues with hostd or vpxa services on ESXi hosts

Resolution

Follow these steps to troubleshoot mass ESXi host "Not Responding" states:

1. Collect initial information:
   a. Note the exact time when the hosts entered the "Not Responding" state.
   b. Identify which hosts were affected.
   c. Check if any VMs were impacted.

2. Review vCenter Server logs:
   a. Access the vCenter Server.
   b. Navigate to the log directory.
   c. Examine vpxd.log for events related to host status changes.

3. Analyze ESXi host logs:
   a. Connect directly to affected ESXi hosts if possible.
   b. Review vmkernel.log and hostd.log files.
   c. Look for error messages or warnings around the time of the status change.

4. Check for network issues:
   a. Review network device logs (switches, routers, firewalls).
   b. Look for any network failover events or configuration changes.
   c. Verify if there were any planned network maintenance activities.
   d. Ensure UDP port 902 is open between ESXi hosts and vCenter Server.

5. Investigate storage-related problems:
   a. Check storage array logs for any failures or performance issues.
   b. Verify if all ESXi hosts can access shared storage.
   c. Look for any storage path failures in ESXi logs.

6. Examine DNS resolution:
   a. Verify DNS server functionality.
   b. Check if ESXi hosts can resolve vCenter Server hostname.
   c. Review DNS configuration on ESXi hosts and vCenter Server.

7. Verify time synchronization:
   a. Check NTP server accessibility and configuration.
   b. Ensure all ESXi hosts and vCenter Server are using the same time source.
   c. Look for time drift issues in ESXi and vCenter Server logs.

8. Assess vCenter Server health:
   a. Review vCenter Server resource utilization (CPU, memory, disk).
   b. Check for any services that may have stopped or crashed.
   c. Verify database connectivity and performance.

9. Check ESXi host services and resources:
   a. Verify the status of hostd and vpxa services on affected hosts.
   b. Note that in cases of mass ESXi "Not Responding" states, service issues are often symptoms rather than causes.
   c. Investigate host resource utilization:
      - Check for memory pressure that could cause services to exceed their resource allotments.
      - Look for CPU saturation that might delay service responses.
   d. Correlate resource issues with network or storage problems:
      - High resource utilization often results from network delays or storage latency.
      - As requests pile up due to these delays, services may become unresponsive.
   e. Focus on resolving underlying network or storage issues identified in steps 4 and 5, as these are likely root causes of service resource problems.
   f. When the storage or network issues are resolved, restart these services if necessary and safe to do so.

10. Implement corrective actions based on findings:
    a. Address any identified network, storage, or configuration issues.
    b. Update firmware, drivers, or software if necessary.
    c. Adjust network topology or failover mechanisms if required.

11. Monitor and verify resolution:
    a. Observe the environment for a period to ensure stability.
    b. Conduct controlled failover tests if appropriate.
    c. Update documentation and runbooks based on findings.

12. Manually reconnect hosts if necessary:
    a. If hosts remain in a "Not Responding" state after resolving underlying issues, right-click on each host in vCenter Server and select "Connect".
    b. In some situations, you may be prompted to enter the ESXi host root user's password
    c. Monitor hosts to ensure they return to a normal connected state.

Additional Information

Understanding the difference between Not Responding and Disconnected ESXi hosts in VMware vCenter Server (KB337333)