This explanation applies to license models where assignment type is set to "device" (i.e. physical machine).
If virtual machines run in a cluster with automatic load balancing, all eligible hosts should be licensed accordingly. It is common practice to restrict licensing to the actual hosts of the virtual machines if evidence for the mobility history is provided accordingly. The licensing logic automatically accounts for the host history which is imported and stored in the system. For each host that has actually run a virtual machine with the relevant software, a license requirement is created. Depending on the license mobility granted within the corresponding license model, the virtual machines within the minimum licensing period are either taken into account to calculate the number of license requirements or not.
The host history of virtual machines is important even without automatic load balancing. If they are moved manually from one host to another host and this is recorded in the runtime logs of the cluster software, this would cause similar problems during an audit.