I noticed quite a bit of network traffic on my switches. I identified the network card that was sending out the broadcasts, it was on a new Windows 2000 with RIS & DHCP installed. It is also a DC. When I do a arp -a I can see hundreds of entries such as 10.0.0.2 0000000000000, where the 0000000000000 should be a MAC address its all zero's which make sense as I only have one PC attached to this server. It is as if it is running through all the possible combinations of the DHCP server and trying to resolve a MAC address.
If I re boot it calms down but start after about ten minutes