Know your gear
CALs are required by Microsoft licensing for all users or devices that access Windows Server Standard or Windows Server Datacenter. When a customer buys Windows Server Standard or Datacenter, they receive a server license that allows them to install the operating system on one computer. A server software license by itself doesn't provide the license rights to allow anyone to connect to that computer, whether they work for the company or not. Instead, each user or device needs a CAL.