In connecting the iSeries via an ethernet, what is the difference between a hub, a managed hub and a switch?
A hub is a single box that connects ethernet devices to each other. In general, a hub is for connecting a small to medium sized office. A managed hub would offer some of the types of services that a router (or switch) would offer. A managed hub might offer forwarding or the capability to mask IP addresses (sharing a single IP). A switch, or router, acts as a gateway server of communications to and from other networks. In a simple scenario, you might have a hub connecting three computers connected to a managed hub that routes to an NT server that is connected to a Cisco router that is connected to the Internet.