How to route to another site through middle site on Fortigate

[Daniel8]

Introduce: 

OS 7.4.6

Site A has 2 tunnel VPN (site-site 1 and site-site 3)

Site B has 2 tunnel VPN (site-site 2 and site-site 3)

Site HO has 2 tunnel VPN (site-site 1 and site-site 2)

Scenario:

- Site A and Site B disconnected tunnel site-site 3

Request:

How to configure routing on 2 tunnel site-site 1 and 2 for Site A can access Site B through site HeadOffice is middle.

#IPsec, #FortiGate

[AEK]

Have you tried by just adding the two static routes through ss1 and ss2 with higher distance?

Doing so should force your FG-40Fs to use ss3 tunnel when its up, and once ss3 is down its route is removed and the FG-40Fs will use the remaining routes ss1 and ss2.

You will also need a firewall rule on FG-100F to allow traffic from site-A to site-B and vice versa.