Ok, ok. Let me search in my little bookmarks archives.
As you want to protect your network from arp spoofing, I advise you firstly to create statics ARP cache (to have secure IP/MAC adresses relations) if your network is stable (understand if you don't change the whole network all the time).
Else, you can try a good IDS well configured (I heard that http://www.snort.com/ has now a arpspoof module to detect such things).
Or you can use dedicated utils like ARPwatch at http://www.firstlinux.com/cgi-bin/pa...nt.cgi?ID=6424 for Linux. There is a such soft for Windows called WinARPwatch but all my links about it are dead and Google didn't find it (sorry).