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HS08
HS08
Valued Contributor
Dec 28, 2025 3:33 PM UTC
Question

Dual ISP

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

3 replies

AEK
SuperUser
AEK
SuperUser
Dec 28, 2025 4:02 PM UTC

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-p/208780

AEK
HS08
HS08Author
Valued Contributor
Dec 28, 2025 4:05 PM UTC

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
SuperUser
Toshi_Esumi
SuperUser
Dec 28, 2025 6:12 PM UTC

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

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