Troubleshooting Tip: Firewall displays warning message with incorrect build number during manual upgrade from v7.4.8 to v7.4.9 despite correct image

When FortiGate product families are first introduced, their supported firmware images typically have different build numbers from those of other, more established FortiGate models. See the article Technical Tip: FortiOS firmware version terminology for more information on NPI and Special Branch builds.

For example, FortiOS v7.4.9 for FortiGate-30G was released in a special branch with build number 6773, see Introduction and supported models. In the Upgrade Path tool, the upgrade path from versions 7.4.8 to 7.4.9 displays the following build details:

When upgrading a device to an NPI image using manual file upload from the GUI, the following warning message may display:

A valid upgrade path cannot be determined for manually uploaded firmware. Ensure that upgrading to FortiOS <new version number> buildXXXX from FortiOS <old version number> buildYYYY is supported, otherwise it may result in the loss of configuration.

Where XXXX shows the branch point build number rather than the build number showing on the uploaded firmware image file, and YYYY correctly shows the current firmware image build number. In the following example taken during a FortiGate-30G upgrade, the build number shown in the warning message is the v7.4.9 GA Release build number 2829.

Even after confirming the upgrade, the firewall continues to display an incorrect build number while uploading the image.

This warning can be safely ignored during the firewall upgrade, provided the correct firmware image was downloaded and uploaded according to the Upgrade Path tool. The upgrade should complete successfully, and the correct build number can be verified after the upgrade.

Note:

If the error 'Image upgrade failed. Failed to upgrade due to expired firmware updates license' is observed, refer to the article: Technical Tip: Failed to upgrade due to 'expired firmware updates license' while upgrading FortiGate 30G/31G from 7.4.8 to 7.4.9 or 7.4.10.