View source for Routers

<i>Article stolen from [http://www.wikipedia.org/ wikipedia]</i>

[[Image:Linksys_router.jpg|right|thumbnail|250px|A Linksys [[Network address translation|NAT]] router, popular for home and small office networks]]

A '''router''' is a [[computer networking device]] that forwards data packets toward their destinations through a process known as [[routing]]. Routing occurs at layer 3 ([[Network layer]]) of the [[OSI seven-layer model]]. 

Routing is most commonly associated with the [[Internet Protocol]], although other less-popular routed protocols remain in use. 

In the original [[1960s]]-era of routing, general-purpose computers served as routers. Although general-purpose computers can perform routing, modern high-speed routers are highly specialised computers, generally with extra hardware added to accelerate both common routing functions such as packet forwarding and specialised functions such as [[IPsec]] encryption. 

Other changes also improve reliability, such as using DC power rather than line power (which can be provided from batteries in data centers), and using solid-state rather than [[magnetic storage]] for program loading. Large modern routers have thus come to resemble [[telephone switch]]es, with whose technology they are currently converging and may eventually replace, whilst small routers have become a common household item.

The first modern (dedicated, standalone) routers were the [[Fuzzball routers]].  

A router can be used to either connect at least two [[computer network|network]]s, or to form a [[mobile ad-hoc network]]. A special variety of router is the [[one-armed router]] used to route packets in a [[virtual LAN]] environment. In the case of a one-armed router the multiple attachments to different networks are all over the same physical link.

A router that connects clients to the Internet is called an ''edge router''. A router that serves to transmit data between other routers is called a ''core router''.
   
A router creates and/or maintains a table, called a "routing table" that stores the best routes to certain network destinations and the "routing metrics" associated with those routes. See the [[routing]] article for a more detailed discussion of how this works.

In recent times many routing functions have been added to [[Local area network|LAN]] [[Network switch|switches]], creating "Layer 2/3 Switches" which route traffic at near wire speed. 

Routers are also now being implemented as [[Internet]] gateways, primarily for small networks like those used in homes and small offices. This application is mainly where the [[Internet]] connection is an always-on broadband connection like [[cable modem]] or [[DSL]]. These are not "routers" in the true sense, but the terminology has been confused with [[network address translation]].

As Routers are costly devices they can't be used generally for education purposes, so simulation software is availaible for this :

eg, Boson Netsim For CCNP

== Router manufacturers ==

* [[3Com]] [http://www.3com.com (www.3com.com)]
* [[Alcatel]] [http://www.alcatel.com (www.alcatel.com)]
* [[Belkin]] [http://www.belkin.com (www.belkin.com)]
* [[Billion]] [http://www.billion.com (www.billion.com)]
* [[Cisco Systems, Inc.]] [http://www.cisco.com (www.cisco.com)]
* [[D-Link Systems]] [http://www.dlink.com (www.dlink.com)]
* [[Enterasys Networks]] [http://www.enterasys.com (www.enterasys.com)]
* [[Huawei | Huawei Technologies]] [http://www.huawei.com (www.huawei.com)]
* [[Juniper Networks]] [http://www.juniper.net (www.juniper.net)]
* [[Linksys]] [http://www.linksys.com (www.linksys.com)]
* [[Mikrotik]] [http://www.mikrotik.com (www.mikrotik.com)]
* [[NETGEAR]] [http://www.netgear.com (www.netgear.com)]
* [[Nortel]] [http://www.nortelnetworks.com (www.nortelnetworks.com)]
* [[Acer (company)|Pivotal Networking]] [http://www.pivnet.com (www.pivnet.com)]
* [[Siemens AG]] [http://www.siemens.com (www.siemens.com)]
* [[SMC Networks]] [http://www.smc.com (www.smc.com)]
* [[Tellabs]] [http://www.tellabs.com (www.tellabs.com)]
* [[MRV Communications]] [http://www.mrv.com (www.mrv.com)]
* Zoom Telephonics [http://www.zoom.com (www.zoom.com)]

== Routing Software ==
<!-- With the proper software, ordinary [[IBM PC|PC]]s can be made into routers: -->
* [http://www.microsoft.com/windowsxp/using/networking/learnmore/ics.mspx Windows XP Internet Connection Sharing]
* [http://www.macdevcenter.com/pub/a/mac/2003/11/11/panther_internet.html Mac OS X Internet Sharing]
* [[Basic Internet Routing Daemon]] [http://bird.network.cz ( bird.network.cz )]
* [[fdgw]]
* [[FREESCO]]
* [[GNU Zebra]] [http://www.zebra.org (www.zebra.org)]
* [[Quagga]] [http://quagga.net/ (quagga.net)]
* [[SmoothWall]] [http://smoothwall.org (smoothwall.org)]
* [[IPCop]] [http://www.ipcop.org (www.ipcop.org)]
* [[The Linux Router Project]]<small><sup>[1]</sup></small>
* [[m0n0wall]] [http://m0n0.ch/wall/ (m0n0.ch/wall)]

<small><sup>[1]</sup></small>Most [[Unix-like]] operating systems include all necessary software to perform routing; the Linux Router Project is an example of a [[Linux distribution]] that specialises in routing.

==See also==
* [[flapping router]]
* [[network address translation]]
* [[Network switch]]

==External links==
*[http://www.bsdrouter.org www.bsdrouter.org] - website that covers router software based on [[Berkeley Software Distribution|BSD]] [[operating system]]s
*[http://computer.howstuffworks.com/router.htm/printable HowStuffWorks: ''How Routers Work'' by Curt Franklin]

==More Links==
*[[Networking]], [[Network Protocols]], [[Network Problems]], [[Network Troubleshooting]]
*[[Wireless Network Security]], [[Wireless Networking]]
*[[Review:Linksys AG241 ADSL2 Modem Gateway]]
*[[DebIPsec]]

[[category:hardware]]
[[category:networking]]