Finally having a switch that sends CDP packets at home, I was looking for more information about the workings of this very informative protocol. CDP has saved me a lot time on finding the switch to configure, while working with Cisco IP telephones, and improper configured switches.
Wondering how I'd be able to gather CDP information with a small device like a cable tester, I came up with this Arduino CDP Sniffer - CdpSniffino.
The CDP implementation is pretty complete, but I'm still working on a nice way to display the information.
You'll need an Arduino, and the Arduino Ethernet shield (or compatible network interface).
These are some idea's of how the information could be displayed on an LCD display (which I have laying around), using sample data from a Cisco IP phone sending CDP packets:
The LCD support is currently a work in progress, and somehow my Arduino freezes after running for a few minutes. On Github, checkout commit 020bf1e257, for a more stable, Serial-output only, version.
If you have any feature or improvement suggestions, please, let me know in the comments below.
Update: continued in Arduino CDP viewer - part 2