In FortiNAC-F, theLayer 3 Network typeis specifically designed for deployments where the isolation networks—such as Registration, Remediation, and Dead End—are separated from the FortiNAC appliance's service interface (port2) by one or more routers. This architecture is common in large, distributed enterprise environments where endpoints in different physical locations or branches must be isolated into subnets that are local to their respective network equipment.
The reason the Configuration Wizard allows for more than one DHCP scope for a single isolation network type (state) is thatthere can be more than one isolation network of each typeacross the infrastructure. For instance, if an organization has three different sites, each site might require its own unique Layer 3 registration subnet to ensure efficient routing and to accommodate local IP address management. By allowing multiple scopes for the "Registration" state, FortiNAC can provide the appropriate IP address, gateway, and DNS settings to a rogue host regardless of which site's registration VLAN it is placed into.
When an endpoint is isolated, the network infrastructure (via DHCP Relay/IP Helper) directs the DHCP request to the FortiNAC service interface. FortiNAC then identifies which scope to use based on the incoming request's gateway information. This flexibility ensures that the system is not limited to a single flat subnet for each isolation state, supporting a scalable, multi-routed network topology.
"Multiple scopes are allowed for each isolation state (Registration, Remediation, Dead End, VPN, Authentication, Isolation, and Access Point Management). Within these scopes, multiple ranges in the lease pool are also permitted... This configWizard option is used when Isolation Networks are separated from the FortiNAC Appliance's port2 interface by a router." —FortiNAC-F Configuration Wizard Reference Manual: Layer 3 Network Section.
