Troubleshooting Tip: Install failed due to vlanid already in use in device by interface

[farhanahmed]

Description	This article describes how to troubleshoot when installing the config to a device fails with the erro: 'invalid value - prop[system interface]: vlanid <id> already in use in device by <interface>'
Scope	FortiManager.
Solution	Verify that the VLAN ID giving the error does not already exist on the FortiGate. If FortiSwitch Manager or System Templates or CLI Templates are used to create VLAN interfaces, make sure VLAN IDs are not re-used. In case FortiSwitches are being used with the FortiGate and the error is for the default VLANs (VLAN-ID: 1, 4088, 4089, 4090, 4091.4092.4093) and go to the device database i.e. Device Manager -> Device & Groups, select the device -> Network -> Interface, select the Interface it gave an error for (VLAN) -> Advance options and make sure to have the switch-controller-feature option set to appropriate VLANs: _default <----- default_vlan (vlanid 1). quarantine <----- quarantine (vlanid 4093). rspan <----- rspan (vlanid 4092). voice <----- voice (vlanid 4091). video <----- video (vlanid 4090). onboarding <----- nac (vlanid 4089). nac_segment <----- nac_segment (vlanid 4088). If all of the above configs are verified and the issue persists, take the backup of FortiManager and contact Fortinet Support TAC. Related articles: Displaying the device database. Technical Tip: The IP Range/Subnet mask of default FortiSwitch VLANs.