Description
It is not possible to register FortiDDNS on another FortiGate unit using the same FQDN. This is because the DDNS entry is already registered to a FortiGate serial number.
This issue normally happens when a FortiGate unit is replaced by another unit following a hardware failure.
Scope
FortiDDNS registration
Solution
This issue can only be resolved by opening a technical assistance ticket with Fortinet. The old and new FortiGate serial numbers and the DDNS hostname should be given in the ticket.
