Thanks guys. I jumped into the gateway router and did a "show arp". That seemed to work for most of the mac's that I needed to lookup. However, some of the mac addresses did not appear in the gateways table. For example, one unmarked line goes into the Catalyst 4006 on port 20. From within the 4006, I did a "show cam dynamic 5/20". This came back with two mac addresses that are assosiated with it. Neither of them are in our gateway's arp table. Can anyone explain?