Enhanced MAC VLANs

The Media Access Control (MAC) Virtual Local Area Network (VLAN) feature in Linux allows you to configure multiple virtual interfaces with different MAC addresses (and therefore different IP addresses) on a physical interface.

FortiGate implements an enhanced MAC VLAN consisting of a MAC VLAN with bridge functionality. Because each MAC VLAN has a unique MAC address, virtual IP addresses (VIPs) and IP pools are supported, and you can disable Source Network Address Translation (SNAT) in policies.

MAC VLAN cannot be used in a transparent mode virtual domain (VDOM). In a transparent mode VDOM, a packet leaves an interface with the MAC address of the original source instead of the interface’s MAC address. FortiGate implements an enhanced version of MAC VLAN where it adds a MAC table in the MAC VLAN which learns the MAC addresses when traffic passes through.

If you configure a VLAN ID for an enhanced MAC VLAN, it won’t join the switch of the underlying interface. When a packet is sent to this interface, a VLAN tag is inserted in the packet and the packet is sent to the driver of the underlying interface. When the underlying interface receives a packet, if the VLAN ID doesn’t match, it won’t deliver the packet to this enhanced MAC VLAN interface.

Note

When using a VLAN ID, the ID and the underlying interface must be a unique pair, even if the belong to different VDOMs. This is because the underlying, physical interface uses the VLAN ID as the identifier to dispatch traffic among the VLAN and enhanced MAC VLAN interfaces.