Upgrade from 6.4.6 straight to 6.4.15 ?

[dataguy]

I have a FortiGate 61F. Can I upgrade from 6.4.6 directly to 6.4.15? 

Has anyone done this without problems?

I am managing it remotely via VPN so I would like to avoid problems that require me to be there to do any physical resets. 

I have asked support as well, but I'm looking for real life experiences/advice.

Thank you !

[AEK]

According to upgrade path tool you need to follow these steps:

6.4.6 -> 6.4.8 -> 6.4.10 M -> 6.4.12 M -> 6.4.14 M -> 6.4.15 M

https://docs.fortinet.com/upgrade-tool/fortigate

Edit: Real life experience is if you don't follow upgrade path then it is probable that you will have a corrupted configuration after the upgrade.

The path is to avoid errors during configuration conversion from version to version.

[amrit]

As mentioned by AEK you need to follow the upgrade path tool.  Additionally 6.4.X is End of support and the 7.0.X is end of engineering support(EOES). So if yo have an active support contract on 61F and the device is in production , I would recommend upgrading either to 7.2.7 or 7.2.8 in 7.2 branch or to 7.4.4 in the 7.4 branch.

We always recommend  console access while performing firmware upgrades activity because if something goes wrong you may lose the access.