You extend a cluster by adding hosts to that cluster. If you previously configured the cluster without setting up the host networking, the configuration of the existing hosts in the cluster is applied to the new hosts.


  • Verify that you have an existing cluster and hosts added to it.
  • During the initial cluster configuration, select the Configure networking settings later check box. For more information, see Configure a Cluster.
  • Verify that hosts have the same ESXi version and patch level.
  • Obtain the user name and password of the root user account for the host.
  • To add a host to a cluster that you manage with a single image, see the Managing Host and Cluster Lifecycle documentation.


  1. In the vSphere Client home page, navigate to Home > Hosts and Clusters and select a configured cluster.
  2. Right-click the cluster and select Add Hosts.
    The Add hosts wizard appears.
  3. On the Add hosts page, add new or existing hosts to the cluster.
    • Add hosts that are not part of the vCenter Server inventory.
      1. Click the New hosts tab.
      2. Populate the IP Address and credentials text boxes for those hosts.
      3. (Optional) To add more new hosts, click the Add Host button.
      4. (Optional) To reuse the credentials for all added hosts, select the Use the same credentials for all hosts check box.
    • Add hosts that are managed by your vCenter Server instance and are in the same data center as your cluster.
      1. Click the Existing hosts tab.
      2. From the list, select the hosts that you want to add to the cluster.
  4. Click Next.
    The Host summary page lists all hosts that will be added to the cluster and related warnings.
    Note: If a host cannot be validated automatically by the system, you are prompted to manually validate its certificate and accept its thumbprint in the Security Alert pop-up.
  5. On the Host summary page, review the details of the added hosts and click Next.
  6. (Optional) On the Import Image page, select the host whose image to use as the image for the cluster.
    The Import Image page appears when you add hosts to a cluster managed with a single image. For information about adding a host to a cluster that you manage with a single image, see the Managing Host and Cluster Lifecycle documentation.
  7. On the Ready to complete page, click Finish.
    The Extend Cluster Guide page appears.
  8. In the Configure hosts card, select Configure.
    A pop-up window appears. It informs you that the configuration for the hosts that exist in the cluster is applied to the newly added hosts.
  9. Select Continue.


After successful validation, your newly added hosts are configured as the existing hosts in your cluster, and the Configure button in the Configure hosts card becomes inactive. You can only click Re-validate to verify the cluster configuration.

What to do next

Configure the host networking manually and add more hosts to the cluster.