What is Router ?

A router interconnects two or more physically and logically separate network segments and iperates at the network layer. Segments are joined together by a router, which maintains a separate logical identity. It constitutes an internetwork--a group of networks linked by a routers. A router distinguishes data packets according to protocol types, such as TCP/IP, IPX/SPX, or Apple Talk. Routers forward traffic according to network level addresses. They can not access to a network, in some cases, depending on the type of application, thus providing a certain measure of securit. This capability is used extensively in creating firewalls, which provide security when an organization is linked to Internet. Also a device that connects two or more different network segments, and allows information to flow between them only when necessary. The router, unlike a bridge, examines the data contained in every packet it receives for detailed information. Based on this information, the router decides whether to block the packet from the rest of the network or transmit it. It also attempts to send the packet by the most efficient path through the network. Routers do this using various routing protocols (mentioned above), the most common among these being RIP, OSPF, and IGRP. Also network layer device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded.