We are in a (painful and lengthy) transition from FortiOS 5.6 to 6.
Next step in the upgrade path is from 5.6.11 tot 6.0.10. Yes, I know, we are 3 years behind... But for us this upgrade to a major version, feels like a giant milestone.
We currently use Forticlient 6.0.3.0155 for VPN (Windows only).
In the release notes for 6.0.10 on page 12 it says:
FortiOS 6.0.10 greatly increases the interoperability between other Fortinet products. This includes:
FortiClient EMS 6.0.8
FortiAP 5.4.4 and later
FortiSwitch 3.6.9 and later
Upgrade the firmware of each product in the correct order. This maintains network connectivity without the need to use manual steps.
On page 16 it says:
If you are using FortiClient only for IPsec VPN or SSL VPN, FortiClient version 5.6.0 and later are supported.
We only use Forticlient for VPN, not endpoint checking.
Will it work ? Or do we have to upgrade Forticlient first ?