Switch: A switch is used to provide additional port, ex-panding the capability of the router. A network switch learns the association between the MAC addresses of connected devices and its switched ports. Router: When connecting more than one device to a modem, a router is generally required. A router acts as the "traffic director" of a network. Modem: A modem is often provided by ISP which enables a network access to the internet. In some cases ISPs provide "hybrid" modem/router combination, this device might be power efficient to some extent.