• An ESXi host shows as "not responding" in vCenter Server.
• An ESXi host shows as disconnected in vCenter Server.
• Cannot connect an ESXi host to vCenter Server.
• Virtual machines on an ESXi host show as greyed out in vCenter Server.
• When attempting to add an ESXi to vCenter Server, you see an error similar to:
  
  Unable to access the specified host, either it doesn't exist, the server software is not responding, or there is a network problem
   
• In the vpxd.log file, you see entries similar to:
   
  • <YYYY-MM-DD>T<time>.696-05:00 [08128 info 'vpxdvpxdMoHost' opID=37D08048-00006071-85] [HostMo] host connection state changed to [DISCONNECTED] for host-26725
    
    </time>
  • <YYYY-MM-DD>T<time>.508-04:00 [04944 error 'vpxdvpxdInvtHostCnx' opID=HB-host-385@3560-79f8b53e] [VpxdInvtHostSyncHostLRO] FixNotRespondingHost failed for host host-385, marking host as notResponding
    <YYYY-MM-DD>T<time>.633-04:00 [00812 error 'vpxdvpxdInvtHostCnx' opID=HB-host-385@3565-12c9cfec] [VpxdInvtHostSyncHostLRO] FixNotRespondingHost failed for host host-385, marking host as notResponding
    
    </time></time>
    For more information, see Location of vCenter Server log files (1021804)
    
    Note: The preceding log excerpts are only examples. Date, time, and environmental variables may vary depending on your environment.

• Validate each troubleshooting step below is true for your environment. 
• Each step provides instructions or a link to another Knowledge Base article to eliminate possible causes. You can take corrective action as necessary. 

VMware ESXi host that is in a "Not Responding" state

ESXi

1. Verify that the ESXi host is accessible from vCenter server or vSphere Client.For more information, see ESX/ESXi hosts do not respond and is grayed out (1019082) 
2. Verify that the ESXi host can be reconnected, or if reconnecting the ESXi host resolves the issue. For more information, see Changing an ESXi or ESX host's connection status in vCenter Server (1003480).
3. Verify that the ESXi host is able to respond back to vCenter Server at the correct IP address. If vCenter Server does not receive heartbeats from the ESXi host, it goes into a not responding state. To verify if the correct managed IP Address is set, see Verifying the vCenter Server Managed IP Address (1008030) and  See also, ESXi host disconnects from vCenter Server after adding or connecting it to the inventory (2040630) and ESXi host keeps disconnecting and reconnecting when heartbeats are not received by vCenter Server (1005757).
4. Verify that network connectivity exists from vCenter Server to the ESXi host with the IP and FQDN. For more information, see Testing network connectivity with the ping command (1003486).
5. Verify that you can connect from vCenter Server to the ESXi host on TCP/UDP port 902. For more information, see Testing port connectivity with Telnet (1003487).
6. Verify if restarting the ESXi Management Agents resolves the issue. For more information, see Restarting the Management agents on an ESXi host (1003490).
7. Verify if the hostd process has stopped responding on the affected ESXi host. For more information, see Troubleshooting vmware-hostd service if it fails or stops responding on an ESX/ESXi host (1002849)  See also : ESXi host is non-responsive and disconnected in ESXi 6.x (56450) 
8. The vpxa agent has stopped responding on the affected ESXi host. For more information, see Troubleshooting the vCenter Server Agent when it does not start (1006128)
9. Verify if the ESXi host has experienced a Purple Diagnostic Screen. For more information, see Interpreting an ESX/ESXi host purple diagnostic screen (1004250)
10. ESXi hosts can disconnect from vCenter Server due to underlying storage issues. For more information, see Identifying Fibre Channel, iSCSI, and NFS storage issues on ESXi/ESX hosts (1003659).

• Español: Diagnósticando un host ESX o ESXi que se desconecta o no responde en vCenter Server (2003724)
• Português: Diagnosticar no vCenter Server um host do ESX ou ESXi que esteja desconectado ou não esteja respondendo (2032480)
• 日本語: vCenter Serverから切断、又は無応答となっているESX・ESXiホストの診断方法 (2013645)
• 简体中文: 诊断在 vCenter Server 中已断开或无响应的 ESXi/ESX 主机 (2048204)