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148 Fortinet Inc.
Virtual domains in Transparent mode Network configuration
To support VLANs in Transparent mode, you add virtual domains to the FortiGate unit.
A virtual domain contains at least 2 VLAN subinterfaces. For VLAN traffic to be able to
pass between the FortiGate Internal and external interface you would add a VLAN
subinterface to the internal interface and another VLAN subinterface to the external
interface. If these VLAN subinterfaces have the same VLAN IDs, the FortiGate unit
applies firewall policies to the traffic on this VLAN. If these VLAN subinterfaces have
different VLAN IDs, or if you add more than two VLAN subinterfaces to the virtual
domain, you can also use firewall policies to control connections between VLANs.
When the FortiGate unit receives a VLAN tagged packet at an interface, the packet is
directed to the VLAN subinterface with matching VLAN ID. The VLAN subinterface
removes the VLAN tag and assigns a destination interface to the packet based on its
destination MAC address. The firewall policies for this source and destination VLAN
subinterface pair are applied to the packet. If the packet is accepted by the firewall,
the FortiGate unit forwards the packet to the destination VLAN subinterface. The
destination VLAN ID is added to the packet and it is sent to the VLAN trunk.
When a packet enters a virtual domain on the FortiGate unit, it is confined to that
virtual domain. In a given domain, you can only create firewall policies for connections
between VLAN subinterfaces or zones in the virtual domain. The packet never
crosses the virtual domain border.
The FortiGate-800 supports 64 virtual domains.
• Virtual domain properties
• Configuring a virtual domain
• Adding firewall policies for virtual domains
• Deleting virtual domains
Figure 31: FortiGate unit with two virtual domains
VLAN1
VLAN1
VLAN2
VLAN2
VLAN3
VLAN3
Virtual Domain 1
Virtual Domain 2
content filtering
antivirus
NIDS
content filtering
antivirus
NIDS
Internal
External
VLAN1
VLAN3
VLAN2
VLAN Switch
or router
VLAN Switch or router
VLAN trunk
VLAN1
VLAN2
VLAN3
VLAN trunk
FortiGate unit
VLAN1
VLAN3
VLAN2
Internet