- Great Painters
- Accounting
- Fundamentals of Law
- Marketing
- Shorthand
- Concept Cars
- Videogames
- The World of Sports

- Blogs
- Free Software
- Google
- My Computer

- PHP Language and Applications
- Wikipedia
- Windows Vista

- Education
- Masterpieces of English Literature
- American English

- English Dictionaries
- The English Language

- Medical Emergencies
- The Theory of Memory
- The Beatles
- Dances
- Microphones
- Musical Notation
- Music Instruments
- Batteries
- Nanotechnology
- Cosmetics
- Diets
- Vegetarianism and Veganism
- Christmas Traditions
- Animals

- Fruits And Vegetables


  1. Adobe Reader
  2. Adware
  3. Altavista
  4. AOL
  5. Apple Macintosh
  6. Application software
  7. Arrow key
  8. Artificial Intelligence
  9. ASCII
  10. Assembly language
  11. Automatic translation
  12. Avatar
  13. Babylon
  14. Bandwidth
  15. Bit
  16. BitTorrent
  17. Black hat
  18. Blog
  19. Bluetooth
  20. Bulletin board system
  21. Byte
  22. Cache memory
  23. Celeron
  24. Central processing unit
  25. Chat room
  26. Client
  27. Command line interface
  28. Compiler
  29. Computer
  30. Computer bus
  31. Computer card
  32. Computer display
  33. Computer file
  34. Computer games
  35. Computer graphics
  36. Computer hardware
  37. Computer keyboard
  38. Computer networking
  39. Computer printer
  40. Computer program
  41. Computer programmer
  42. Computer science
  43. Computer security
  44. Computer software
  45. Computer storage
  46. Computer system
  47. Computer terminal
  48. Computer virus
  49. Computing
  50. Conference call
  51. Context menu
  52. Creative commons
  53. Creative Commons License
  54. Creative Technology
  55. Cursor
  56. Data
  57. Database
  58. Data storage device
  59. Debuggers
  60. Demo
  61. Desktop computer
  62. Digital divide
  63. Discussion groups
  64. DNS server
  65. Domain name
  66. DOS
  67. Download
  68. Download manager
  69. DVD-ROM
  70. DVD-RW
  71. E-mail
  72. E-mail spam
  73. File Transfer Protocol
  74. Firewall
  75. Firmware
  76. Flash memory
  77. Floppy disk drive
  78. GNU
  79. GNU General Public License
  80. GNU Project
  81. Google
  82. Google AdWords
  83. Google bomb
  84. Graphics
  85. Graphics card
  86. Hacker
  87. Hacker culture
  88. Hard disk
  89. High-level programming language
  90. Home computer
  91. HTML
  92. Hyperlink
  93. IBM
  94. Image processing
  95. Image scanner
  96. Instant messaging
  97. Instruction
  98. Intel
  99. Intel Core 2
  100. Interface
  101. Internet
  102. Internet bot
  103. Internet Explorer
  104. Internet protocols
  105. Internet service provider
  106. Interoperability
  107. IP addresses
  108. IPod
  109. Joystick
  110. JPEG
  111. Keyword
  112. Laptop computer
  113. Linux
  114. Linux kernel
  115. Liquid crystal display
  116. List of file formats
  117. List of Google products
  118. Local area network
  119. Logitech
  120. Machine language
  121. Mac OS X
  122. Macromedia Flash
  123. Mainframe computer
  124. Malware
  125. Media center
  126. Media player
  127. Megabyte
  128. Microsoft
  129. Microsoft Windows
  130. Microsoft Word
  131. Mirror site
  132. Modem
  133. Motherboard
  134. Mouse
  135. Mouse pad
  136. Mozilla Firefox
  137. Mp3
  138. MPEG
  139. MPEG-4
  140. Multimedia
  141. Musical Instrument Digital Interface
  142. Netscape
  143. Network card
  144. News ticker
  145. Office suite
  146. Online auction
  147. Online chat
  148. Open Directory Project
  149. Open source
  150. Open source software
  151. Opera
  152. Operating system
  153. Optical character recognition
  154. Optical disc
  155. output
  156. PageRank
  157. Password
  158. Pay-per-click
  159. PC speaker
  160. Peer-to-peer
  161. Pentium
  162. Peripheral
  163. Personal computer
  164. Personal digital assistant
  165. Phishing
  166. Pirated software
  167. Podcasting
  168. Pointing device
  169. POP3
  170. Programming language
  171. QuickTime
  172. Random access memory
  173. Routers
  174. Safari
  175. Scalability
  176. Scrollbar
  177. Scrolling
  178. Scroll wheel
  179. Search engine
  180. Security cracking
  181. Server
  182. Simple Mail Transfer Protocol
  183. Skype
  184. Social software
  185. Software bug
  186. Software cracker
  187. Software library
  188. Software utility
  189. Solaris Operating Environment
  190. Sound Blaster
  191. Soundcard
  192. Spam
  193. Spamdexing
  194. Spam in blogs
  195. Speech recognition
  196. Spoofing attack
  197. Spreadsheet
  198. Spyware
  199. Streaming media
  200. Supercomputer
  201. Tablet computer
  202. Telecommunications
  203. Text messaging
  204. Trackball
  205. Trojan horse
  206. TV card
  207. Unicode
  208. Uniform Resource Identifier
  209. Unix
  210. URL redirection
  211. USB flash drive
  212. USB port
  213. User interface
  214. Vlog
  215. Voice over IP
  216. Warez
  217. Wearable computer
  218. Web application
  219. Web banner
  220. Web browser
  221. Web crawler
  222. Web directories
  223. Web indexing
  224. Webmail
  225. Web page
  226. Website
  227. Wiki
  228. Wikipedia
  229. WIMP
  230. Windows CE
  231. Windows key
  232. Windows Media Player
  233. Windows Vista
  234. Word processor
  235. World Wide Web
  236. Worm
  237. XML
  238. X Window System
  239. Yahoo
  240. Zombie computer

This article is from:

All text is available under the terms of the GNU Free Documentation License: 


From Wikipedia, the free encyclopedia

(Redirected from Routers)
This article is about a computer networking device. For the kind of rotating cutting tool called wood router, see wood router.
A rack-mounted Virtual Access router in use in an ISP's data center
A rack-mounted Virtual Access router in use in an ISP's data center

A router (pronunciation: [raʊtɚ] or [ruːtɚ]) is a computer networking device that forwards data packets across a network toward their destinations, through a process known as routing. Routing occurs at Layer 3 (the network layer i.e. Internet Protocol (IP)) of the OSI seven-layer protocol stack.


Routers are like intersections whereas switches are like streets
Routers are like intersections whereas switches are like streets

A router acts as a junction between two or more networks to transfer data packets among them. A router is different from a switch. A switch connects devices to form a local area network (LAN).

One easy illustration for the different functions of routers and switches is to think of switches as neighborhood streets, and the router as the intersections with the street signs. Each house on the street has an address within a range on the block. In the same way, a switch connects various devices each with their own IP address(es) on a LAN.

However, the switch knows nothing about IP addresses except its own management address. Routers connect networks together the way that on-ramps or major intersections connect streets to both highways and freeways, etc. The street signs at the intersection (routing table) show which way the packets need to flow.

So for example, a router at home connects the Internet service provider's (ISP) network (usually on an Internet address) together with the LAN in the home (typically using a range of private IP addresses, see network address translation (NAT)) and a single broadcast domain. The switch connects devices together to form the LAN. Sometimes the switch and the router are combined together in one single package sold as a multiple port router.

In order to route packets, a router communicates with other routers using routing protocols and using this information creates and maintains a routing table. The routing table stores the best routes to certain network destinations, the "routing metrics" associated with those routes, and the path to the next hop router. See the routing article for a more detailed discussion of how this works.

Routing is most commonly associated with Internet Protocol(IP), although other less-popular routed protocols are in use.

Types of routers

A basic home router connects an ethernet network to a broadband connection. These routers will typically include connectors for both networks (13, 17), along with a basic processor (4), RAM (6), and flash memory (7).
A basic home router connects an ethernet network to a broadband connection. These routers will typically include connectors for both networks (13, 17), along with a basic processor (4), RAM (6), and flash memory (7).
The setup menu for a typical consumer router.
The setup menu for a typical consumer router.

In the original era of routing (from the mid-1970s through the 1980s), general-purpose mini-computers served as routers. The ARPAnet (the Internet's predecessor) used what was then called IMPs. 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 switches, with whose technology they are currently converging and may eventually replace. Small routers have become a common household item.

A router that connects clients to the Internet is called an edge router. A router that serves solely to transmit data between other routers, e.g. inside the network of a ISP, is called a core router.

A router is normally used to connect at least two networks, but 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.

In mobile ad-hoc networks every host performs routing and forwarding by itself, while in wired networks there is usually just one router for a whole broadcast domain.

In recent times many routing functions have been added to LAN switches (a marketing term for high-speed bridges), 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 routers in the true sense because they join two networks together - the WAN and the LAN and have a routing table. Often these small routers support the RIP protocol, although in a home application the routing function does not serve much purpose since there are only two ways to go - the WAN and the LAN. In addition, these routers typically provide DHCP, NAT, DMZ and firewall services. Sometimes these routers can provide content filtering and VPN. Typically they are used in conjunction with either a cable or DSL modem, but that function can also be built-in.

Larger routers are typically found in data centers. They join multiple networks together with a lot of bandwidth. Depending on their function, these routers will support any number of routing protocols including IS-IS OSPF IGRP EIGRP RIP BGP and EGP.

Manufacturers of routers

There are a number of manufacturers of routers including:

  • 3Com
  • Actiontec
  • Alcatel
  • Apple Computer
  • Asus
  • Belkin
  • Billion
  • Bountiful Wifi
  • Buffalo Technology
  • Eurotronic Products GmbH
  • Cisco Systems
  • D-Link Systems
  • Draytek
  • Enterasys Networks
  • Extreme Networks
  • Foundry Networks
  • Hewlett-Packard
  • Huawei Technologies
  • Juniper Networks
  • Kentrox
  • Lightning MultiCom
  • Linksys
  • Lucent Technologies
  • Mikrotik
  • Motorola
  • MRV Communications
  • Netgear
  • Netopia
  • Nortel
  • Pivotal Networking
  • PacketFront
  • Redback Networks
  • Siemens AG
  • Tellabs
  • U.S. Robotics
  • ZyXEL


"Software" routers

With the proper software and 2 or more network cards, ordinary PCs, even old ones, can be made into routers.

Most Unix-like operating systems include all necessary software to perform routing:

  • LEAF Project
  • Coyote Linux
  • GNU Zebra
  • SmoothWall
  • m0n0wall
  • FreeBSD
  • NetBSD
  • OpenBSD
  • IPCop
  • The Linux Router Project
  • fdgw
  • ClarkConnect
  • Vyatta OFR which is a small distribution based on XORP
  • ZeroShell a small Linux distribution which is able to act as router, bridge and VPN box

The list includes only some examples that specialise in routing. NAT has been a built-in function of the Linux kernel since version 1.3. Originally an option that needed to be compiled into the kernel, most modern versions have NAT as a module that merely needs to be turned on. See List of Linux distributions, BSD, Unix-like for more.

Other solutions include:

  • Microsoft Internet Connection Sharing (only some routing capabilities)
  • WOOWEB-PRO (Windows software)
  • Mac OS X Internet Sharing

See also

  • Flapping router
  • Network address translation (NAT)
  • Network bridge
  • Network switch
  • History of the Internet
  • Wi-Fi
  • TR-069
  • Central Outdoor Router

External links

  • Huawei Technologies Home Page
  • Cisco Systems Home Page
  • Tutorials related to working with routers
  • How Routers Work (HowStuffWorks)
  • OpenWrt is a Linux distribution for embedded devices
Retrieved from ""