Fortigate Trunk port.

Forum|Forum|6 months ago
February 12, 2026
3 replies
297 views

Hello everyone,

I have a FortiSwitch where all VLANs are configured and working correctly.

However, the customer has requested a contingency scenario:

If the FortiSwitch goes down, they want to be able to connect another switch directly to the FortiGate, using a trunk port with the same VLANs.

The question is:

How should the FortiGate port be configured so it can operate as a trunk interface carrying the same VLANs currently defined on the FortiSwitch?

brandonziots

Explorer

Are you using Fortilink to connect the FortiSwitch to FortiGate? If so, any VLANs built on that Fortilink interface will automatically trunk to the switchport. Just make sure your additional firewall ports have been added/associated with your Fortilink interface.

jpapicAuthor

Explorer

I added my lan3 to the fortlink, my questio now will be, if i connect a switch (not fortiswitch) to the lan3 will this have all the vlans and work as a trunk? can I have any lacp issue?
Thanks.

brandonziots

Explorer

Yes you can trunk VLANs via a standard LAN port or a Fortilink port. Mixing switches on the same aggregate interface is where problems arise. Please see this post for more details: https://community.fortinet.com/t5/Support-Forum/Trunk-between-Cisco-switch-and-Fortigate-using-LACP/td-p/292805
Unfortunately I don't have a Cisco switch to lab this out with but I would assume you will see problems after the switchover to the Cisco switch based on the post above.
Maybe somebody with a Cisco switch can lab it out and chime in here.

Sign up

Login with SSO

Login to the community

Login with SSO