>I've discovered a rouge device on our network and I know it's mac address (using Netstumbler). How do I determine the IP address from the MAC address?
The lookups are done the other way; if a machine wants to send data to another machine, it uses ARP (the address resolution protocol) to ask: "who is IP #...?" (ARP request), and the machine that has this IP address replies: "My MAC address is..." (ARP reply).
I don't know of an easy way to do the search the way you want; perhaps some packet tracer can help identify packets that have the desired MAC address, and then you can investigate the packet, which will most likely contain an IP address, too.
Because of this kind of problems, the MAC addresses vs. IP addresses should be documented somewhere; but of course, many companies don't take the trouble to do this.
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