Troubleshooting Tip: FortiLink aggregate interface is down, causing Authorized/down FortiSwitch status

[skrymi]

Description	This article describes how to resolve an issue where the FortiSwitch status shows as 'Offline' after upgrading FortiGate.
Scope	FortiGate 7.4.5, 7.6.0 and FortiSwitch 7.6.0.
Solution	After deploying a new firmware version on the FortiGate, the managed FortiSwitch status is Authorized/Down and FortiLink aggregate interface cannot link UP:  On the FortiGate side:  execute switch-controller get-conn-status <FortiSwitch_serial_number> Admin Status: Authorized / down Connection: Idle To further diagnose the connection: execute switch-controller diagnose-connection <FortiSwitch_serial_number> No IP address retrieved for FortiSwitch <FortiSwitch_serial_number> Remote Address: N/A Status ... Idle From the configuration of the FortiLink aggregate interface, the management VLAN ID should be checked: config system interface edit " fortilink" show full ……  set switch-controller-mgmt-vlan 4094    <- This is the default management VLAN on FortiGate. …… On the FortiSwitch side: config switch auto-network After rebooting the switch, the output from the command is as follows: config switch auto-network set mgmt-vlan 1 <- The management VLAN on FortiSwitch is switched to VLAN 1. set status enable For this reason, FortiSwitch cannot get the IP address from the FortiLink aggregate interface, and the following change should be made in order to fix the issue: config switch auto-network set mgmt-vlan 4094 set status enable end