The FortiGuard DDNS can be configured when using a private IP address on the “wan” interface in order to get management access to a FortiGate.Solution
1. Configure a private IP address on the “wan” interface. Note that the FortiGate must be behind a NAT device using a public IP address.
2. Go to System > DNS and configure the following:
a) Select an Interface
b) Select “Use Public IP Address”
c) Select the “Unique Location”, for example fgtest.
After this has been configured it should be possible to access the FortiGate using “fgtest.fortiddns.com”.