Error: vSphere HA reports that an agent is in the Agent Unreachable state

Products

• VMware vCenter Server 6.0
• VMware vCenter Server 7.0
• VMware vCenter Server 8.0
• VMware vSphere ESXi 6.0
• VMware vSphere ESXi 7.0
• VMware vSphere ESXi 8.0

Issue/Introduction

Symptoms : 

• The vSphere HA agent is unreachable
• In the Summary tab of the affected ESXi host, you see the error:
  

  vSphere HA reports that an agent is in the Agent Unreachable state

• Restarting the management agents does not resolve the issue
• Restarting the Virtual Center service does not resolve the issue
• The fdm logs may include the below entries 

  Failed to SSL handshake; SSL.
  YYYY-MM-DDTHH:MM:SS Er(163) Fdm[2101520]: --> The remote host certificate has these problems:
  YYYY-MM-DDTHH:MM:SS Er(163) Fdm[2101520]: --> 
  YYYY-MM-DDTHH:MM:SS Er(163) Fdm[2101520]: --> * Host name does not match the subject name(s) in certificate.
  YYYY-MM-DDTHH:MM:SS Er(163) Fdm[2101520]: --> 
  YYYY-MM-DDTHH:MM:SS Er(163) Fdm[2101520]: --> * unable to get local issuer certificate)
  YYYY-MM-DDTHH:MM:SS Er(163) Fdm[2101520]: --> [context]zKq7AVECAQAAABiabwEKZmRtAID8eoEBZmRtAIAbU2oBgHifagGApKJqAYBapGoBgJ4GbAGAgDdsAYBL1IwBAVJ4AGxpYnB0aHJlYWQuc28uMAACDzIPbGliYy5zby42AA==[/context] on handshake
  
  

Follow this article for specific error vSphere HA agent for this host has an error. The vSphere HA agent is not reachable from vCenter server.

Environment

VMware vCenter Server 6.x

VMware vCenter Server 7.x

VMware vCenter Server 8.x

Cause

This issue occurs if there is a network problem that prevents vCenter Server from contacting the primary host and the agent on the host or if all hosts in the cluster have failed. This issue may also occur if the agent on the host has failed and the watchdog process is unable to restart it.

The SSL Certificate does not match to the PNID of the PSC Node, please check the Subject Alternative Name is same as the PNID of PSC.

Resolution

To resolve this issue:

1. Determine if vCenter Server is reporting the host as Not Responding. For more information, see Diagnosing an ESX or ESXi host that is Disconnected or Not Responding in vCenter Server (1003409).
2. If the host is in a Not Responding state, there is a network problem or a total cluster failure. After you resolve this condition, vSphere HA should configure correctly.
3. If the vCenter Server reports the hosts as responding:
   • Enable the SSH access to the host.
   • Connect to the ESXi host using SSH.
   • Review the /var/log/vpxa.log file and check if there are errors related to communication with vCenter Server and the host Management Agent (hostd).
   • Review the /var/log/fdm.log file (Fault Domain Manager log) and check if there are errors related to vSphere High Availability. For more information, see the vSphere Availability Guide
4. Right-click the affected host and click Reconfigure for vSphere HA.

For additional troubleshooting information, see:

• Guidelines for Troubleshooting

Additional Information

For more information, see:

• Error: "vSphere HA agent cannot be correctly installed or configured"