Router : What is a Router and How it Works

Router are network devices that manages computer networks’ incoming packets according to the IP addresses and either connects them or disconnects them. Long ago we wrote what are hub, switch and router and this is the Router is a part of that article. The the incoming packets are actually analyzed according to to OSI layer 3 model.

Basics of a Router

Router operates at layer 3 of the OSI reference model as said above. A router have a plurality of interfaces, these interfaces can also be virtual. On the arrival of data packets, a router based on the OSI layer 3 destination address (eg IP address) determine the destination and thus it determines the appropriate interface via which the data are to be forwarded. For this purpose it uses a locally available routing table that indicates which port of the router (or any intermediate station) of network is accessible.

Router can only be suitable for routing data packets of routable protocols, such as IP ( IPv4 or IPv6 ) or IPX / SPX. Other protocols, such as the original MS-DOS and MS-Windows NetBIOS and NetBEUI protocols, which were meant only for small networks and from their design are not routable are not forwarded by a router. Packets from these protocol families are usually  based on layer 2 , so they will work with switches.

Types of Router

Backbone router or Hardware router : The high speed router on the Internet (or in large enterprises) are now highly dependent on packet forwarding optimized devices that can route many Gigabit of data throughput per second in hardware, ie, the processing power is a significant part of specific network interfaces that is provided locally. The individual ports or interfaces can independently receive and send data. They are either have an internal high-speed bus) or crosswise connected to each other. In general, such devices are designed for continuous operation (99.999% or higher) and have redundant hardware (power supplies, etc.) in order to avoid loss of connectivity. Also, it is common to have hot swappable components for these routers. In the early days of computer networking, it was against common standard workstations to use as a router, which was implemented by the routing software.

Border router or edge router : Mostly used by the Internet service providers ( ISPs ). On these routers, they mostly run the routing protocol BGP . For data transfer between peers usually EBGP (External Border Gateway Protocol) is used, this allows the router to transfer data to a neighboring autonomous system.

DSL Router : A router that has a PPPoE client to dial into the Internet via xDSL to one ISP. Often these DSL routers are as multifunction devices with a switch, a WLAN access point, often with a small PBX, a VoIP gateway and / or a DSL modem (xDSL any type).

There are actually other Types of Routers, including software router, we have deliberatively avoided them to keep the understanding simple to an average user.