Technical Tip: How to re-establish connection between FortiGate and FortiManager after uploading new license file on FortiManager

1. When the FortiGate has been onboarded into FortiManager, the FortiManager's Serial Number will be recognized and displayed on the FortiGate’s central-management CLI:

2. Verify the connection is Connected/UP on the FortiGate and FortiManager.

3. Each license file is linked to a unique FortiManager Serial Number. Hence, if a new license file is uploaded into FortiManager, the device’s Serial Number will change and will affect the connectivity between FortiManager and FortiGate.

4. This is because the FortiManager's Serial Number has been changed to FMG-VMXXXXXX2724, but the FortiGate is still recognizing the old Serial Number.

5. To rectify this, navigate to Device Manager -> 'Right-click' the FortiGate -> Edit -> Re-key the admin password -> OK -> 'Right-click' the FortiGate again -> Refresh Device. After that, verify that FortiManager successfully updates the device information, and on the FortiGate side, check whether the new FortiManager Serial Number is being reflected.

6. Alternatively, log in to FortiGate and manually register the new Serial Number as follows:

execute central-mgmt register-device <FMG Serial Number> fortinet  <----- Register the new Serial Number.
fnsysctl killall fgfmd  <----- Restarts the FGFM tunnel.

diagnose fdsm central-mgmt-status  <----- Check the connection and registration status.

Note: If the FortiGate is a VM device, in the FortiManager CLI, enable recognition of FortiGate-VM serial numbers:

config sys global
    set fgfm-allow-vm enable
end

Related article:

Technical Tip: How to register a FortiGate to a FortiManager from CLI