Technical Tip: The proper way to remove the Trunk link between FortiSwitches

1. Given the network topology, by default, the connection between the Core-switch and Access-switch is 'Inter-Switch-Link' (ISL), with lldp-profile of 'default-auto-isl' on port1 of both FortiSwitches:

2. The proper way to remove this trunk link is:

    

Step 1: Change the lldp-profile in the leaf (or downstream) switch.

config switch-controller managed-switch
    edit <access-SW>       --> For the above example: S124EF4N17000159.
        config ports
            edit port1
                set lldp-profile default
        end
end

Step 2: Change the lldp-profile in the CORE (or upstream) switch:

config switch-controller managed-switch
    edit <CORE-SW>       --> For above example: S124FFTF23014945.
        config ports
            edit port1
                set lldp-profile default
        end
end

With this order, the ISL trunk should be deleted in 1-2 minutes in the FortiSwitch, so that the FortiGate GUI page will reflect faster.