Finally, I have decided to take 5 minutes and focus on the gratuitous ARP broadcast issue I have with our Windows 2000 server (Fujitsu Siemens server).
The problem is described here : http://blog.wains.be/post/unsolvable-gratuitous-arp-from-our-windows-2000-server-with-intel-pro-1000/
I have installed Wireshark on the Windows box, had to reboot (oh !) to get it working. Thanks to Wireshark, I figured out the gratuitous ARP traffic was generated as some lower level than Windows.
Indeed, the whole network is seeing the gratuitous ARP broadcast except the Windows box. Conclusion : the broadcast is not generated by the OS but probably by the hardware itself.
I have checked the BIOS for any interesting setting but I don’t find anything relevant. The BIOS is really minimal actually.
I found another person having the same issue with the same network interface : http://techrepublic.com.com/5208-6230-0.html?forumID=101&threadID=224471&messageID=2245929
I will avoid Fujitsu Siemens for servers in the future : cheap RAID controller (Promise), Maxtor drives, minimal BIOS, etc.
Next : figuring out why the Windows printer spooler randomly stops working (printing blank pages actually), restarting the service fixes the issue….. (edit : seems fixed by updating the drivers while the changelog didn’t mention the issue, damn HP)