Finding the switch port you are plugged into
LLDP and CDP discovery: what it needs, how long it takes, and when it stays empty.
Before you start
- Npcap installed
- A wired connection to the switch
Switches broadcast their own identity on the wire. Port Finder listens for those frames and reports what they say — the switch name, the physical port, the port description the network team wrote, the native VLAN and the switch’s management IP.
Nothing is sent to the switch to make this happen. The frames are already there.
Using it
- Plug into the port you want to identify.
- Open Port Finder. It starts listening on every adapter at once, so a laptop on Ethernet and Wi-Fi shows both.
- Wait. Frames arrive on the switch’s timer, typically every 30 to 60 seconds. A freshly plugged lead can take that long to produce anything.
Advertising this PC
Advertise this PC sends LLDP from your machine, so the switch — and anyone looking at its neighbour table — can see you. Useful when the question is being asked from the other end.
When nothing appears
The honest answer is that a switch with LLDP and CDP disabled says nothing, and no amount of waiting changes that. Other causes worth ruling out first are in troubleshooting: no Npcap, a dock or unmanaged switch in the path that does not forward the frames, or listening on the wrong adapter.