GUI

Workflow

1. Pick an interface. The dropdown shows every NIC on your machine. Use the toggle to hide interfaces with no IP. Hit the ↻ button to re-scan after plugging or unplugging cables.
2. Pick the protocol. LLDP is the universal choice (Aruba, HP, Juniper, Extreme, Mikrotik, Cisco). CDP is Cisco-only.
3. Click Start. Most switches send a discovery packet every 30–60 seconds, so it usually takes a few seconds for the first frame to arrive.
4. Read the result. Switch name, IP, port, VLAN, voice VLAN, MTU, and model populate the result card.

Privilege warnings

PortFinder shows a banner if it can't capture packets:

• macOS — click Install BPF Access once. The app installs a LaunchDaemon that makes /dev/bpf* readable for members of the access_bpf group, which Wireshark also uses.
• Linux — install the .deb or .rpm package. The postinstall sets CAP_NET_RAW on the binary so it doesn't need sudo.
• Windows — install Npcap with "Allow non-administrators to capture" enabled.

Sniff all interfaces

Selecting Sniff all Interfaces runs a capture on every non-loopback NIC in parallel and returns the first matching packet. Useful when you don't know which physical port is patched into the switch.