Which installation is necessary for implementing pass-through authentication in Azure AD?

To implement pass-through authentication in Azure Active Directory (Azure AD), the installation of Azure AD Connect is necessary. Azure AD Connect is a tool that facilitates the integration of on-premises directories with Azure AD. It enables hybrid identity solutions, allowing users to use the same credentials on both their local Active Directory and Azure AD.

Pass-through authentication works by authenticating users directly with their on-premises Active Directory credentials without the need for them to be stored in the cloud. When you install Azure AD Connect, it establishes a secure connection to synchronize user identities and to enable authentication methods like pass-through authentication.

While other options may involve various configurations, they are not specifically essential for implementing pass-through authentication. For instance, active directory configuration could be a part of the broader setup but does not directly implement this mechanism by itself. Service Principal Name setup and virtual machine setups are also not directly relevant to the process of pass-through authentication in Azure AD.