What is one of the first steps in upgrading an existing forest?

Creating new domain-joined virtual machines (VMs) or physical servers is indeed one of the initial steps when upgrading an existing Active Directory forest. This approach allows for a smooth transition because it provides a testing environment for the new version before fully committing to the upgrade.

By establishing new domain-joined servers, administrators can evaluate the compatibility of existing applications and services with the new directory version. This step ensures that any potential issues are addressed early in the migration process, minimizing disruptions to users and services. Furthermore, it allows teams to configure new servers without affecting the existing infrastructure, thereby maintaining operational continuity.

This method also offers the opportunity to implement best practices and assess resource allocation or hardware requirements based on the latest features and improvements of the newer Active Directory version. In doing so, organizations can effectively plan for scaling or necessary changes in their environments while preparing for a full forest upgrade.

The other choices serve important roles in the process but are not typically the first steps. For instance, demoting existing domain controllers is a later step that often occurs after the new servers are set up. Reviewing licensing requirements and notifying users about downtimes are essential preparations but generally follow the establishment of new servers that will host the upgraded forest.