Ettercap will still only work if you use ARP Poisoning on the system you wish to look at. It would still be a switched network. Also on a switched network you can use any sniffer and will pick up multicast traffic, so it would appear that you were seeing traffic, which you are, you just aren't seeing ALL traffic. Ettercap is a choice prog for ARP Poisoning, but you have to make sure that your system, which is running ettercap, will be able to route for the system you have poisoned. Correct me if I'm wrong on these points.....