HOW TO
Find which switch port a cable is plugged into
For when the job is: Work out where a wall port lands without tracing the cable.
An unlabelled wall port, a patch panel nobody has updated since 2019, and a switch in a cupboard two floors up. The usual answers are tracing the cable, using a toner, or logging into every switch and reading the MAC address table.
There is a faster one. Most managed switches announce themselves continuously on every port using LLDP, or CDP on Cisco kit — the switch's name, the exact interface the frame came out of, the native VLAN and often a management IP. Plug a laptop into the wall port, listen for one of those frames, and the switch tells you where you are.
CySecTek's Port Finder does exactly that: it listens on the wire and reports what the switch said. No console cable, no credentials on the switch, no tracing.
What CySecTek does here
- Reports switch name, physical port (for example GigabitEthernet1/0/14), native VLAN and management IP.
- Reads both LLDP and CDP, so it works on Cisco kit that only speaks CDP.
- Nothing needed on the switch: no login, no SNMP community, no configuration change. It only listens to what is already being broadcast.
- Useful in the other direction too — confirming a patch before you label it, or checking which VLAN a port is actually in rather than what the documentation claims.
What it will not do
- It needs the free Npcap driver, because reading raw LLDP and CDP frames is not something ordinary sockets can do.
- It cannot help if the switch has LLDP and CDP both disabled, or if there is an unmanaged switch between you and the managed one — you will see the far switch, not the dumb box in the middle.
- Advertisements are periodic, typically every 30 to 60 seconds, so it is not instant. Leave it listening for a minute.
Questions
- Do I need access to the switch?
- No. That is the point — no login, no SNMP community, no configuration change. The switch is already announcing this on every port; the tool just listens.
- How long does it take?
- As long as it takes the switch to send its next advertisement, usually 30 to 60 seconds. Leave it running while you do something else.
- Does it work with Cisco?
- Yes. Cisco kit often has CDP enabled and LLDP off, so both are read.
- Why does it need a driver?
- LLDP and CDP frames are not IP traffic, so a normal socket never sees them. Npcap is free, and it is the same driver Wireshark uses.
Free, and one download
CySecTek 0.7.0 for Windows 10 and 11, 64-bit. No account, no licence key, no paid tier. The installer's SHA-256 is published beside it so you can verify what you downloaded.
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