The FortiNAC-F Logical Network feature is specifically designed to provide an abstraction layer between high-level security policies and the underlying physical network infrastructure. In large-scale deployments where different physical locations (like Building 1, 2, and 3 in the exhibit) use different local VLAN IDs for the same type of device (e.g., VLAN 10, 20, and 30 for printers), managing separate policies for each building would create significant administrative overhead.
By using a Logical Network, an administrator can create a single entity-for example, a logical network named "Printers"-and use it as the "Access Value" in a single Network Access Policy. The mapping of this logical label to a specific physical VLAN occurs at the Model Configuration level for each network device. When a printer connects to a switch in Building 1, FortiNAC-F evaluates the policy, identifies that the printer should be in the "Printers" logical network, and checks the Model Configuration for that specific switch to see which VLAN ID is mapped to that label (VLAN 10). If the same printer moves to Building 3, the same single policy applies, but FortiNAC-F provisions it to VLAN 30 based on the local mapping for that building's switch.
This architectural approach ensures that policies remain consistent and easy to manage regardless of the complexity or variations in the local network topology.
"Logical Networks provide a way to define a network access requirement once and apply it across many different network devices that may use different VLAN IDs for that access... Each managed device can use different VLAN IDs for the same Logical Network label. You can define the Logical Networks based on requirements and then associate the network to a VLAN ID when the managed device is configured in the Model Configuration." - FortiNAC-F IoT Deployment Guide: Define the Logical Networks.