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Arif69
Staff
Arif69
Staff
June 9, 2026

Technical Tip: FortiManager's behavior of installing Policy Package with same VLAN ID used in FortiSwitch VLANs and Network Interface

  • June 9, 2026
  • 1 reply
  • 39 views

Desription


This article describes FortiManager's behavior of installing Policy Package with same VLAN ID used in FortiSwitch VLANs and Network Interface.


Scope


FortiManager.


Solution


The following diagram shows interface 'Interface A' in device 'FGT A', which has a VLAN ID 306:

70dc0421.png


So, this is the VLAN ID 306 used in the Network Interface.


Next, the same device of 'FGT A' contained some FortiSwitches. FortiSwitch C has a template called 'Template C':


86c5c0cc.png


In 'Template C', it contains multiple Switch VLAN assignments, which in this case, port 41 is assigned with 'VLAN ABCD':

Under FortiSwitch Manager -> FortiSwitch VLANs, VLAN ABCD is using VLAN ID 306 as well:

3fa7d2ed.png


So, this is the VLAN ID 306 used in FortiSwitch VLANs.

When installing Policy Package for 'FGT A', FortiManager will show the error as follows:

7a0014e9.png

      1 reply

      C
      CharithG
      New Member
      June 25, 2026

      The same VLAN ID can be used for both a FortiGate VLAN interface and a FortiSwitch VLAN, if they have the same VLAN name.

      For example, VLAN 306 can be created on the FortiGate under the FortiLink interface and also as a FortiSwitch VLAN.
      This is a common design when the FortiGate acts as the Layer 3 gateway for that VLAN while the VLAN is extended to FortiSwitch access ports through FortiLink.
      As long as the VLAN name and VLAN ID match on both the FortiGate interface and the FortiSwitch VLAN object in FortiManager, the configuration should work correctly and is not considered a duplicate VLAN.

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