PortFinder

PortFinder, published by packetThrower and currently at version 4.1.4 (one of three released versions), is a network switch port discovery tool that identifies which switch, switchport, and VLAN a machine is currently plugged into. Rather than querying infrastructure actively, it works passively: the tool listens for the discovery packets that the switch is already broadcasting, requiring only a 30-second listen on the wire. This approach means no agent needs to be installed on the switch, no SNMP access is required, and no login credentials are necessary, making it useful for field technicians, network administrators, and support staff who need to document or troubleshoot physical network connections without privileged access to switching equipment. PortFinder falls within the network diagnostics and discovery category, with typical use cases including cabling audits, port mapping, VLAN verification, and on-site troubleshooting. Protocol support covers three discovery standards: LLDP, which is universal and supported by Aruba, HP, Juniper, Extreme, Cisco, and MikroTik equipment; CDP for Cisco environments; and MNDP as a MikroTik RouterOS fallback, ensuring broad compatibility across mixed-vendor networks. The software ships as a single binary containing both a desktop graphical interface and a headless command-line interface, allowing it to serve interactive users as well as scripted or automated workflows. The CLI is invoked with a command such as `portfinder capture --interface --protocol LLDP [--json]`, where the optional JSON output flag supports integration with other tools and data pipelines. On Windows, non-administrator capture requires Npcap to be installed with the "Allow non-administrators to capture" option enabled. With its passive design, multi-protocol support, and dual-interface delivery, PortFinder provides a lightweight, low-friction way to answer the common question of exactly where a device connects to the network.

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