Martian Source detection

Hello, in the network of my company the firewall based on SuSE 7.0 the following kernel warning appears from time to time: Nov 14 16:03:35 dbwwall kernel: martian source 4796a8c0 for ff64a8c0, dev eth0 Nov 14 16:03:35 dbwwall kernel: ll header: ff ff ff ff ff ff 00 a0 f9 00 d0 57 08 00 I know what matian sources are. My question is, how I can find out the device or intruder, which causes the trouble. Which tool can I use to find the listed mac-address in my Network? Thanks in advance! Rainer Frohne