VM licenses are only applied in ISE 2.4
https://www.cisco.com/c/en/us/td/docs/security/ise/2-4/release_notes/b_ise_24_rn.htmlLicenses for VM nodes
Cisco ISE is also sold as a virtual appliance. For Release 2.4, it is recommended that you install appropriate VM licenses for the VM nodes in your deployment. You must install the VM licenses based on the number of VM nodes and each VM node's resources such as CPU and memory. Otherwise, you will receive warnings and notifications to procure and install the VM license keys in Release 2.4, however, the services are not interrupted. Starting from Cisco ISE 2.4, you can now manage your VM licenses.
VM licenses are offered under three categories—Small, Medium, and Large. For instance, if you are using 3595 equivalent VM node with 8 cores and 64 GB RAM, you might need a Medium category VM license, if you want to replicate the same capabilities on the VM. You can install multiple VM licenses based on the number of VMs and their resources as per your deployment requirements.
VM licenses are Infrastructure licenses, therefore, you can install VM licenses irrespective of the endpoint licenses available in your deployment. You can install a VM license even if you have not installed any Evaluation, Base, Plus, or Apex license in your deployment. However, in order to use the features enabled by the Base, Plus, or Apex licenses, you must install the appropriate licenses.
After installing or upgrading to Release 2.4, if there is any mismatch between the number of deployed VM nodes and installed VM licenses, alarms are displayed in the Alarms dashlet for every 14 days. Alarms are also displayed if there are any changes in the VM node’s resources or whenever a VM node is registered or deregistered.
VM licenses are perpetual licenses. VM licensing changes are displayed every time you log in to the Cisco ISE GUI, until you check the "Do not show this message again" check box in the notification popup.
If you have not purchased any ISE VM license before, refer to the ISE Ordering Guide<> to choose the appropriate VM license to be purchased. If you have purchased ISE VM licenses with no Product Authorization Key (PAK) associated, you can request VM PAKs by reaching out to ise-vm-license@cisco.com with Sales Order numbers that reflect the ISE VM purchase. This request will be processed to provide one medium VM license key for each ISE VM purchase you made in the past.
The following table shows the minimum VM resources by category:
