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Handbook

Unknown VLANs and VLAN forwarding

6.0.0
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Unknown VLANs and VLAN forwarding

When a FortiGate receives a tagged frame with an unknown VLAN ID, traffic can be handled one of two ways, depending on whether VLAN forwarding is enabled or disabled.

By default, VLAN forwarding is disabled and any frames that are tagged with an unknown VLAN ID are dropped by the FortiGate.

If you enable VLAN forwarding, frames tagged with an unknown VLAN ID are forwarded from the port that received the frames to all other ports in the same forwarding domain(s). This allows you to insert the FortiGate between two devices using trunk ports without any further configuration.

Unknown VLANs and VLAN forwarding

When a FortiGate receives a tagged frame with an unknown VLAN ID, traffic can be handled one of two ways, depending on whether VLAN forwarding is enabled or disabled.

By default, VLAN forwarding is disabled and any frames that are tagged with an unknown VLAN ID are dropped by the FortiGate.

If you enable VLAN forwarding, frames tagged with an unknown VLAN ID are forwarded from the port that received the frames to all other ports in the same forwarding domain(s). This allows you to insert the FortiGate between two devices using trunk ports without any further configuration.