A network router is a network device with interfaces in multiple networks whose task is to copy packets from one network to another.

Routers operate at Layer 3 of the OSI Model, the Network Layer. This is in contrast to switches, which operate at Layer 2 of the OSI Model, the Data-Link Layer.

A network router will typically utilize one or more routing protocols, such as RIP, OSPF, or BGP. Routers also accept routes which are configured manually by a network administrator. Those routes are called static routes.

The router will use this information to create a routing table.

The network router will then use its routing table to make intelligent decisions about which packets to copy to which of its interfaces.

This process is known as routing.

Routers are available with many types of interfaces, such as Ethernet and DSL. Wireless routers support wireless interfaces, such as 802.11 (Wi-Fi).

Routing software makes it possible to build a fully functional router out of a normal computer.