Dual ISP

[HS08]

When i have dual ISP, let say ISP-A and ISP-B then which ISP will be used for forti DDNS source?

[AEK]

The interface is selected in the DDNS config, as show in the tech tip.

https://community.fortinet.com/t5/FortiGate/Technical-Tip-How-to-configure-Dynamic-DNS-FortiGate/ta-...

[HS08]

Example I set ISP-A and ISP-B on the interface, then forti ddns will use ISP-A and if ISP-A down then the record will use public ip from ISP-B?

[Toshi_Esumi]

As the KB @AEK referred, you have to specify a unique name for each interface/ISP, like "isp-a.fortiddns.com" and "isp-b.fortiddns.com", which can be used to set up like IPsec or other VPN connection from outside.
In other words, both are up unless you configured for the secondary to be down while the primary is up.

Toshi