Once the licensing mode is selected and configured on the RD Session Host, changing from Per Device to Per User (or vice versa) requires significant reconfiguration and is generally restricted by the license terms.

…that user or device requires an RDS CAL.

Organizations with Windows Server 2012 RDS CALs have specific downgrade rights. This means if you have purchased 2012 CALs, you can use them to access Windows Server 2008 R2 or 2008 RDS environments, provided you follow the installation procedures for the older OS version but register the CALs using the 2012 licensing server logic (or downgrade the CALs themselves via Microsoft support).

Need help with Microsoft licensing? Always consult a certified Microsoft Licensing Solution Partner (LSP) for your specific environment.

The is not an optional add-on—it is a mandatory license for any organization providing remote desktop access beyond basic server management. Choosing the right licensing model (Per User vs. Per Device) and correctly installing CALs on a License Server ensures both legal compliance and uninterrupted remote access.