A more precise definition of a router is a computer networking device that interconnects separate logical subnets. Routers are now available in many types, though all are fundamentally doing the same job. A router is a computer whose software and hardware are usually tailored to the tasks of routing and forwarding, generally containing a specialized operating system (e.g. Cisco's IOS), RAM, NVRAM, flash memory, and a small processor. However, with the proper software (such as XORP or Quagga), even commodity PCs can act as routers.
Routers connect to two or more logical subnets, which do not necessarily map one-to-one to the physical interfaces of the router.[2]
The term switch or layer 3 switch or network switch often is used interchangably with router, but switch is really a marketing term without a rigorous technical definition (though a switch is commonly understood as a network hub with switched ports, which might or might not also perform additional routing functions).
