Because ESXi does not support vCenter Single Sign-On, it does not support the identity sources you set up with vCenter Single Sign-On. You can add an ESXi host to an Active Directory Domain from the vSphere Web Client.
- In the vSphere Web Client, select the ESXi host.
- In the Settings tab, select Authentication Services in the System area.
- Click Join Domain, supply the domain settings, and click OK.