In the FortiOS graphical user interface under the "FortiSwitch Ports" section, a specific visual indicator is used for Inter-Switch Links (ISLs). When a managed FortiSwitch port is connected to an adjacent managed FortiSwitch, the FortiGate automatically forms a trunk for the ISL. To quickly visually identify this topology, the GUI replaces the standard Native VLAN text with a link icon alongside the serial number of the adjacent FortiSwitch. Therefore, the presence of the serial number "S424DPTF20000027" and the link icon on port23 confirms that this port connects directly to a neighboring managed FortiSwitch bearing that specific serial number.

A: The port is not a dedicated management interface. Management interfaces utilize specific VLANs but do not automatically display adjacent device serial numbers with a link icon in this column.

C: The displayed serial number belongs to the adjacent connected switch. It does not belong to the local Access-1 switch, which possesses a distinctly different serial number ending in 29.

D: Standalone unmanaged switches do not form FortiLink ISLs. The link icon and adjacent serial number confirm the connected device is a managed FortiSwitch participating in the FortiLink topology.

Fortinet Document Library. "FortiSwitch Manager Administration Guide 7.2.5." Operation and Maintenance: Port List Display, pp. 149-150.

Fortinet Document Library. "FortiSwitchOS 7.4.1 FortiLink Guide." Devices Managed by FortiOS: Managed FortiSwitch Display.