Diagnosing the vSphere Client when it fails to connect to an ESX/ESXi host or vCenter Server

Symptoms

• vCenter Server cannot connect to the ESX/ESXi host.
• Connecting vCenter Server to the ESX/ESXi host fails.
• vSphere Client cannot connect to the ESX/ESXi host.
• You see one or more of these errors:
  
  
  • Login failed
  • Login failed due to a bad username or password
  • Cannot complete due login due to an incorrect username or password
  • Timed out waiting for server response
  • Failed To Connect to host

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1003870

http://kb.vmware.com/selfservice/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=1003490

Restarting the Management agents on ESXi

To restart the management agents on ESXi:

From the Direct Console User Interface (DCUI):

1. Connect to the console of your ESXi host.
2. Press F2 to customize the system.
3. Log in as root.
4. Use the Up/Down arrows to navigate to Restart Management Agents.
   
   Note: In ESXi 4.1 and ESXi 5.0, 5.1 and 5.5, this option is available under Troubleshooting Options.
5. Press Enter.
6. Press F11 to restart the services.
7. When the service has been restarted, press Enter.
8. Press Esc to log out of the system.