recommended fortinet version

Hi Team,

You can follow the below link to check the suitable upgraded version
https://docs.fortinet.com/upgrade-tool

In the current product : please select the product .

In current Fortios version: select the current firmware version you have.

upgrade the fortios version: select the recommended one.

Let us know if you have any further concerns.

If you're looking for guidance regarding what firmware has been the most trouble-free across the breadth of documented functionality, I know 6.4.6 is solid.  We've moved most of our fleet to 6.4.9, so have about 4 weeks experience on this release and thus far we have not encountered any show stoppers.  I will update in 4 weeks time when we've completed the upgrade on our most complicated units.

Update: I can confirm 6.4.9 appears to work well, even on 1500D units with lots of functionality enabled (BGP, FortiWiFi, IPSec, FortiEMS, RADIUS, LDAP, SDWAN, etc.).  Be sure to carefully review upgrade notes from 6.0 to 6.2 and 6.2 to 6.4.  I do recall a change in SSL/TLS for LDAPS as well as removal of device groups, so if those are in use, you should prepare/adjust accordingly.