Troubleshooting Tip: Managed FortiSwitches goes to offline state on the FortiGate after core FortiSwitch is rebooted in FortiOS v7.6.7

Description

This article describes an issue where managed FortiSwitches go offline on FortiGate running version 7.6.7 after a Core FortiSwitch is rebooted or upgraded.

Scope

FortiGate v7.6.7 and a managed FortiSwitch.

Solution

This issue is fixed in FortiGate v7.6.8 and v8.0.1.

Workaround:

If the issue is encountered on FortiGate v7.6.7, try the following workarounds:

• Disable and re-enable the FortiLink interface.
  
  

config system interface
edit fortilink
set status down
end

Then:

config system interface
edit fortilink
set status up
end

• Change the LACP mode of the FortiLink interface to static.

config system interface
edit "fortilink"
set lacp-mode static
next
end

• Perform an HA failover on the FortiGate.
  
  

execute ha failover set <cluster_id>

• Downgrading individual device firmware

If any of the above workarounds do not help, collect the following CLI debug logs:

diagnose debug disable
diagnose debug reset
diagnose debug application fortilinkd -1
diagnose debug console timestamp en
diagnose debug en

To stop the debug:

diagnose debug disable