Troubleshooting Tip: FortiSwitches go offline after FortiOS update to v7.6.4 or later

This issue affects interfaces matching the following configuration.

config system interface

    edit "flink-hw-switch"

        set fortilink enable

        set type hard-switch <-- Does not affect interfaces with default type 'aggregate'.

    next

end

With the affected configuration, after upgrading from previous firmware versions to FortiOS v7.6.4 to v7.6.6, the FortiLink interface shows as online in the FortiOS network interfaces GUI, but all switches show offline, and data traffic does not pass.

Execute the command below to verify the FortiSwitch Status via CLI:

execute switch-controller get-conn-status <FortiSwitch Switch-ID>

Get managed-switch <FortiSwitch Switch-ID> connection status:

Admin Status: Authorized
Connection: Idle (capwap)

Diagnosing...
Checking fortilink status: pass.
Checking caputp status...
System error.

Workaround:

To resolve the issue of FortiSwitches going offline after updating the FortiGate to v7.6.4, v7.6.5, or v7.6.6, enable the Spanning Tree Protocol (STP) setting on the hardware switch FortiLink interface.

From CLI:

config system interface

    edit <FortiLink_hardware_switch_interface>

        set stp enable

    next

end

From GUI:

After enabling STP, the FortiSwitches should come back online.

If there is no access to FortiGate to configure STP but FortiSwitches are accessible, configure the uplink to FortiGate as a Static ISL trunk as shown in Configuring FortiLink.

Resolution:

This issue is scheduled for fix in FortiOS v7.6.7 and later, currently scheduled for release in late April 2026. Firmware release dates are subject to change without notice. The issue is also resolved in the upcoming FortiOS v8.0.0.

Related articles:
Troubleshooting Tip: Fix FortiSwitch showing with the 'Offline' status

Technical Tip: Upgrading FortiOS with FortiLink-enabled FortiSwitches