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

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Article ID: 308932

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Updated On:

Products

VMware vSphere ESXi

Issue/Introduction

This article provides steps to troubleshoot connectivity issues to an ESXi host from the vSphere Web Client by verifying network connectivity, authentication and permissions.

  • The vCenter Server or vSphere web client cannot connect to an ESXi host.
  • Connecting the vCenter Server to an ESXi host fails.
  • One or more of these errors is displayed:
    • 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

Environment

VMware vSphere ESXi

Resolution

Please validate that each of the troubleshooting steps below. Each step provides instructions or a link to a KB or a document to eliminate possible causes and take corrective action as necessary. The steps are ordered in the most appropriate sequence to isolate the issue and identify the proper resolution. Do not skip a step.

Note: When performing a corrective action in any of the following steps, attempt to reconnect the ESXi host with the vCenter.
  1. Confirm connection to the correct hostname or IP address for the vCenter Server. Connections fail because incorrect server information may make the problem seem more complex than it is. Correct any incorrect names and try connecting to vCenter Server with the vSphere Client. If the connection fails using the hostname but succeeds with IP address, then it is probably a DNS error that needs to be corrected.  Check both forward and reverse DNS zones.

    1. To check that DNS resolves correctly on the vCenter for the host run commands on the ESXi host:
      nslookup <FQDN of vCenter server>

nslookup <IP of vCenter server>
    2. To check that DNS resolves correctly on the host for the vCenter execute these commands on the vCenter server:
      dig <FQDN of ESXi host>

dig -x <ip of ESXi host>

       

  2. Verify that network connectivity exists from the client workstation to the ESXi host. 
  3. Verify that the ESXi Server Management service on the ESXi host is running. For more information, see Restarting the Management agents on an ESXi or ESX host.

  4. Verify connectivity from the vCenter Server to the ESXi host on port 902 TCP. By default, ESXi listens on port 902 and therefore if the previous steps are all correct it most means that a physical firewall is blocking connectivity on port 902. For more information, see Testing port connectivity with Telnet.

  5. Verify connectivity from ESXi host to vCenter server on port 902 UDP using the following command on the ESXi host:
    nc -zu <ip of vCenter server> 902


  6. Verify the correct username and password are being used. Often, an incorrect username or password has been specified causing the log on failure to occur with the error: Cannot complete login due to an incorrect user name or password.

  7. Verify that the configured permissions for the account are sufficient to allow logging in to the ESX/ESXi host. For more information, see Troubleshooting permissions errors when connecting to an ESX/ESXi host with the vSphere/Virtual Infrastructure client.

Additional Information

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