Network router

A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet. A data packet is typically forwarded from one router to another router through the networks that constitute the internetwork until it reaches its destination node.

A router is connected to two or more data lines from different networks. When a data packet comes in on one of the lines, the router reads the address information in the packet to determine the ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. This creates an overlay internetwork.

The most familiar type of routers are home and small office routers that simply pass IP packets between the home computers and the Internet. An example of a router would be the owner's cable or DSL router, which connects to the Internet through an Internet service provider (ISP). More sophisticated routers, such as enterprise routers, connect large business or ISP networks up to the powerful core routers that forward data at high speed along the optical fiber lines of the Internet backbone. Though routers are typically dedicated hardware devices, software-based routers also exist.

When multiple routers are used in interconnected networks, the routers can exchange information about destination addresses using a dynamic routing protocol. Each router builds up a routing table listing the preferred routes between any two systems on the interconnected networks.

A router may have interfaces for different physical types of network connections, such as copper cables, fibre optic, or wireless transmission. Its firmware can also support different networking standards. Each network interface is used by this specialized computer software to enable data packets to be forwarded from one protocol transmission system to another.

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