I don't know whether you are working on a multilayer switch like the 3550, or a layer-2 switch like the 2950.

If you are using a layer-2 switch, then there is bad news: the method you suggest will not work too well either. The reason is that the arp cache will show you only those hosts that are talking to the switch itself, i.e. management stations, and not the hosts that are talking through the switch. For the hosts talking through the switch, the switch does not need to know anything about the IP-to-MAC mapping, so the ARP cache will be almost empty.

In this case, your best bet is to get the IP-to-MAC mapping by looking at the ARP cache on your router, then going to your switch to map the MAC address to the switch port. This does kind of assume that the host is using the router to get out of its subnet - if not you are out of luck. You could also ping the host from a PC on the same subnet, then look at the ARP cache on the PC.

If you have a multilayer switch, then at least both router and switch functions are in the same box, which makes life easier.

Also, if you have a Network Management System, this will usually do such tasks for you.

Hope this helps.

Kevin Dorrell

Luxembourg