Virtual clustering VLAN/VDOM limitation

In a FortiGate 6000F virtual clustering configuration, a VLAN must be in the same virtual cluster as the physical interface, LAG, or redundant interface that the VLAN has been added to. The VLAN can be in the same VDOM as its physical interface, LAG, or redundant interface or in a different VDOM, as long as both VDOMs are in the same virtual cluster.

If virtual clustering has already been set up, when adding VLANs, GUI and CLI error checking prevents you from adding a VLAN to a VDOM that is in a different virtual cluster than the physical interface, LAG, or redundant interface that you are attempting to add the VLAN to. However, error checking can't prevent this problem if you configure the VLANs before setting up virtual clustering or if you move VDOMs to different virtual clusters after adding the VLANs.

A recommended strategy for preventing this problem could involve the following steps:

1. Start by setting up virtual clustering before creating new VDOMs.
2. Create a placeholder VDOM and add it to virtual cluster 2.

3. Separate traffic interfaces between the root VDOM in virtual cluster 1 and the placeholder VDOM in virtual cluster 2.

   Based on network planning you can create an even distribution of planned traffic volume between the two virtual clusters.

4. Build up your configuration by adding more VDOMs, LAGs, redundant interfaces, and VLANs as required, making sure to keep VLANs in the same virtual cluster as their parent interfaces, LAGs, or redundant interfaces.

Example incorrect VLAN configuration

Consider the following FortiGate 6000F virtual clustering example, which shows how traffic can be blocked by this limitation:

• Three data traffic VDOMs: root, Engineering, and Marketing.
• One LAG interface: LAG1 in the root VDOM.
• Two VLAN interfaces added to LAG1: vlan11 and vlan12.
  • vlan11 is added to the Engineering VDOM.
  • vlan12 is added to the Marketing VDOM.
• The root and Engineering VDOMs are in virtual cluster 1.
• The Marketing VDOM is in virtual cluster 2.

As a result of this configuration:

• vlan11 is in the Engineering VDOM, which is in virtual cluster 1. vlan11 is also in LAG1, which is in the root VDOM, also in virtual cluster 1. vlan11 and its LAG are in the same virtual cluster. Traffic can pass through vlan11.
• vlan12 is in the Marketing VDOM, which is in virtual cluster 2. vlan12 is also in LAG1, which is in the root VDOM, in virtual cluster 1. vlan12 and its LAG are in different virtual clusters. Traffic cannot pass through vlan12.