Technical Tip: FortiGate VM Decreases Active CPUs to 1 After License Change

License Types Overview:

FortiGate-VM licenses are available in the following formats:

Trial Licenses (V-Series):

• FGVM00********. 00 indicates the number of CPUs allowed by the license.
• FGVMEV********.

Subscription Licenses (S-Series): FGVMSL********.

FortiFlex Licenses:

• Flexible consumption-based licenses.
• Note: FortiFlex licenses are not covered by this article.

Behavior description:

When a FortiGate-VM license is approaching expiration, it must be renewed or replaced.

• If the same license type is renewed (e.g., V-Series to V-Series), the serial number (SN) remains unchanged, and no CPU impact is expected.
• If a V-Series license is upgraded to an S-Series license, the SN changes due to the license type change.

The serial number change causes the FortiGate-VM to be treated as a new deployment.

As a result, after the license is uploaded and the first mandatory reboot is executed, the VM may be limited to 1 CPU, even if the license entitlement allows more. This behavior is intentional and designed to prevent system instability by avoiding the immediate application of additional CPU resources.

The initial reboot is required to:

• Validate the new license.
• Register the new serial number.

However, the licensed CPU resources are not fully applied until a second reboot is performed to activate the full license entitlement.

Additional notes:

• No data loss or configuration impact occurs during this process.
• Always ensure the hypervisor is configured to allow at least the number of CPUs specified by the license.

Related documents:

VM License 7.6.5

Technical Tip: How to add CPU core in FortiGate firewall VM