I have a similar problem. Somewhere on our network there is a RAS that's bugging my SCO UNIX box every few seconds. The result is the bootp program filling the syslog with error messages about a bad address from this MAC address. The address is 52.41.53... and that's a RAS. But I can't find this offending device by the MAC address.
I found some software that hunts down all the MAC addresses on my subnet, but no further.
Total non Perl reply, but just a reply to try and help you:
There is no way that you can find MAC addresses outside
your subnet, in fact,all ARP and RARP requests are limited to the segment(s) you`re in...(searching from)