|  |  | A switched network is set up very similarly to a hub-based Ethernet network, but as the name implies, it uses a switch instead of a hub. The switch can either be preprogrammed with the unique hardware identifiers of the nodes attached to it, or the switch can learn the identifiers. When system A wants to communicate with system D, it sends its packet to the switch, which consults its switching table and then forwards the packet out of the appropriate port. By restricting where the packet is sent we not only increase security, but network performance as well.