ESXi hosts are licensed with vSphere licenses. Each vSphere license key has a certain processor capacity that you can use to license multiple physical processors on ESXi hosts. When you assign a vSphere license key to a host, the amount of processor capacity that is consumed is equal to the number of physical processors in the host
To license an ESXi host, you need to assign it a vSphere license key with processor capacity that is sufficient to license all physical processors on the host. For example, to license two ESXi hosts that have four processors each, you need to assign a vSphere license key with a minimum capacity of 8 processors to the hosts.
If you try to assign a license key that has insufficient capacity to license all physical processors on the host, the license assignment is unsuccessful. In such case, you need to assign a different license key with a larger processor capacity. You need to use a different license key in your inventory or combine your license key with another license key to create a new license key with a larger processor capacity.
You can assign and reassign the processor capacity of a vSphere license key to any combination of ESXi hosts. For example, suppose that you purchase a vSphere license key for 10 processors. You can assign the license key to any of the following combinations of hosts:
Five 2-processor hosts.
Three 2-processor hosts and one 4-processor host.
Two 4-processor hosts and one 2-processor host.
One 8-processor host and one 2-processor host.
Dual-core and quad-core processors, such as Intel processors that combine two or four independent processors on a single chip, count as one processor.