The diagram shows a FortiGate connected to two FortiSwitches, which suggests the use ofFortiLink, Fortinet's protocol for managing switches directly from a FortiGate. Since multiple connections are being used, the LAN interface must be set to802.3ad (LAG)mode to aggregate the links for redundancy and load balancing.

This setup allows FortiGate to handle VLAN assignments dynamically, as seen withVLAN 10 (192.168.15.1/24). FortiLink ensures seamless integration between FortiGate and FortiSwitches, making STP unnecessary because Fortinet'sMCLAGprevents loops at Layer 2. SD-WAN, on the other hand, is used for WAN interfaces and does not apply to switch connectivity in this scenario.

The output of the get router info ospf status command provides key information about the OSPF (Open Shortest Path First) configuration on the FortiGate device.

The FortiGate device is connected to multiple areas

● The output states: "This router is an ABR"

●ABR (Area Border Router)means the device is connected tomultiple OSPF areasand maintains routing information between them.

● This confirms that the FortiGate isnot just in one area, but at leastone backbone area (Area 0) and another OSPF area.

The FortiGate device injects external routing information

● The output states: "Supports opaque LSA"

●Opaque LSAs(Type 9, 10, and 11) are used inOSPF extensions, including those that support external route injection.

● Typically, ABRs or ASBRs (Autonomous System Boundary Routers)inject external routes, allowing routes fromother routing protocols (such as BGP or static routes) to be advertised into OSPF.

In atransparent mode Virtual Domain (VDOM)configuration, FortiGate operates as aLayer 2 bridgerather than performing Layer 3 routing. Theset forward-domain <domain_ID>command is used to control how traffic is forwarded between interfaces within the sametransparent VDOM.

Aforward-domainacts as abroadcast domain, meaning only interfaces with thesame forward-domain IDcan exchange traffic. This setting is commonly used toseparate different VLANs or network segmentswithin the transparent VDOM while still allowing FortiGate to apply security policies.