An error event 'Agent can't send heartbeats: Host is down' is recorded while vCenter is down.

Products

• VMware vSphere ESX 8.x
• VMware vSphere ESX 7.x

Issue/Introduction

Prerequisites:

• The vCenter Server Appliance (VCSA) was powered off for maintenance work.
  
  
• The ESXi hosts managed by vCenter remained operational.
  
  
• After starting the vCenter Server Appliance, the following error event was observed on specific hosts:
  
  

  Date Time:
   MM/DD/YYYY, hh:mm:ss
  Type:
   Error
  Target:
    [ESXi host name]
  Description:
  Error detected on  [ESXi host name] in [Data Center] : Agent can't send heartbeats: Host is down
  Event Type Description:
  An error occurred on the host
  Possible Causes:
  • The agent cannot send heartbeats because of a networking related failure on host
  • The agent failed to update the configuration file on host
  • The agent failed to save the configuration file to disk on host
  • The provisioning module failed to load. As a result, all provisioning operations will fail on host.
  Related events:
  There are no related events.
  

• The vpxa.log of the ESXi host that reported the error shows the following entries recorded periodically while vCenter was down:
  
  

  YYYY-MM-DDTHH:MM:SS.sssZ Er(163) Vpxa[525463]: [Originator@6876 sub=Heartbeat opID=vpxaHeartbeat.cpp:218-54f9b715] Agent can't send heartbeats: Host is down

 

Environment

VMware vSphere ESX 8.x 

VMware vSphere ESX 7.x 

Cause

ESXi hosts periodically send heartbeats to vCenter via UDP. If an ESXi host determines that it cannot communicate with vCenter for heartbeat transmission—due to reasons such as vCenter downtime—the relevant error event will be output.

Resolution

If this error event was output due to a vCenter shutdown, it can be safely ignored.

Additional Information

ESXi host showing not responding in vCenter cluster due to physical switch(s) reboot