Different Network Structure
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Both interfaces on the same subnet. Say 172.20.1.0/30
Routed package on pfsense.
https://kb.fortinet.com/kb/documentLink.do?externalID=FD30031
Then you allow networks from the other side to reach via firewall rules.

You will probably have to allow the pfsense traffic on the Fortinet side as well.
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Have you set up the interfaces that you show connected in your picture above?
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I fail ignorant :(
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First set up your spare interfaces like this and connect them together.

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Add the "Routed" package.

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Set up the "Routed" package on the pfsense router and choose the interface that connects to the other Fortinet Router. Pick a password that both sides will share.

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@chpalmer said in Different Network Structure:
Use this document to help you with the Fortinet router and setting up RIP on it.
https://kb.fortinet.com/kb/documentLink.do?externalID=FD30031
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If you don't have spare interfaces.. this could be done via a VPN from one WAN to the other WAN..
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Will it work if we connect two devices with port and write route ?
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@ahmetakkaya said in Different Network Structure:
Will it work if we connect two devices with port and write route ?
Yes. The routed package writes the route for you. But it can be all done manually..