Issue: Cannot change Fortigate from NAT to transparent mode. Error getting from the GUI is “value conflicts with system settings”.
Platform: Fortinet Fortigate UTM firmware 5.x.
Solution: Converting Fortigate from NAT to transparent mode from the GUI gives me this error “value conflicts with system settings” which isn’t helpful. I tried looking for dependencies but can’t find anything wrong. So I tried converting Fortigate from NAT to transparent through CLI hoping to get different and meaningful error message. After trying I get what I was expecting:
Cannot change to transparent mode because this vdom contains the following virtual switch: lan
I proceeded deleting security policy related to “lan” and break the virtual switch.