Troubleshooting Tip: FortiSwitch cannot come online on FortiGate

[laltuzar]

Description

This article describes how to fix when a FortiSwitch cannot come online on FortiGate. When running the command 'execute switch-controller diagnose-connection <FSW_SN>' it displays the following output:

FGT-RAU-1 # execute switch-controller diagnose-connection S124E**********

Fortilink interface ... OK
fortilink enabled
WARNING : VLAN interface for default vlan-id is missing ... please check config <-

DHCP server ... OK
fortilink enabled
WARNING : NTP service for DHCP entry should be set to local mode .... please check config <-

…

Scope

FortiGate-60F-7.0.9.

FortiSwitch-124E-FPOE v7.2.3.

Solution

During the remote session, the customer did not have a VLAN 1 created. Let’s remember that by default it is generated on FortiGate and should not be used for any other purpose different than for FortiLink.

No VLAN 1 on FortiSwitch VLANs

On the CLI, there was a VLAN with the name '_default' and vlanid1 but when trying to modify the VLAN id with the command vlanid x, the process fails:

VLAN _default could not be modified

So a new VLAN was created with the name vsw.fortilink, although the name could have been any other.

VLAN 1 created from scratch

After the VLAN was created, the message 'WARNING : VLAN interface for default vlan-id is missing ... please check config' on the FortiLink diagnose connection disappeared; now it was time to fix the DHCP warning.

VLAN error does not appear anymore

The DHCP server (in this case it was the number 30) is configured, so it ended like this:

DHCP server configuration

config system ntp
    set ntpsync enable
    set type fortiguard
    set syncinterval 60
    set source-ip 0.0.0.0
    set source-ip6 ::
    set server-mode enable
    set authentication disable
    set interface "fortilink"
end

config system dhcp server
    edit 30
        set dns-service local
        set ntp-service local
        set default-gateway 172.19.X.X
        set netmask 255.255.255.0
        set interface "fortilink"
            config ip-range
                edit 1
                    set start-ip 172.19.X.X
                    set end-ip 172.19.X.X
                next
            end
        set vci-match enable
        set vci-string "FortiSwitch" "FortiExtender"
    next
end

After configuring it, reboot the FortiSwitch to default settings again to trigger the FortiLink process again. After this, the issue got resolved. FortiSwitch came online on FortiGate and on CLI:

FortiLink came up on CLI

FortiLink came up GUI