Troubleshooting Tip: Internal interface native VLAN changes after switch reboot

sachitdas_FTNT · ‎06-02-2023

Description

This article describes how to consider if FortiSwitch's internal interface native VLAN changes to a different VLAN after the switch reboot

Scope

FortiSwitch v7.2.x and above.

Solution

Starting from FortiSwitch 7.2.0, 'auto-network' feature has been introduced. Refer to the link:

https://docs.fortinet.com/document/fortiswitch/7.2.0/release-notes/10296/special-notices

By default, this is enabled for FortiSwitch to come up in FortiLink mode and the mgmt-vlan is set to 4094:

https://docs.fortinet.com/document/fortiswitch/7.2.3/fortiswitchos-cli-reference/511852/config-switc...

So, after a FortiSwitch reboot, the switch's internal interface native VLAN is changed to 4094.

Command:

show full-config switch interface internal

If the FortiSwitch runs in standalone mode, it is possible to disable this feature.

config switch auto-network

set status disable

end

If the FortiSwich is used in 'Fortilink over layer3' mode and if a different native VLAN needs to be configured on internal interface, then change the mgmt-vlan.

For example:

On FortiSwitch:

config switch auto-network

set mgmt-vlan 1

set status enable

end

On FortiGate:

config system interface

edit <fortilink interface name>

set switch-controller-mgmt-vlan 1

end