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[[File:SPOF.png|thumb|Computers connected to a server using a router]]
A '''router''' is a [[computer]] whose software and hardware are customized to move data between computer networks. They are responsible for making sure traffic between computers gets where it needs to go. They do this by choosing the shortest path between the computers using a complicated system of rules called [[routing protocol]]s. Routers generally contain a specialized [[operating system]], [[random access memory|RAM]], [[NVRAM]], [[flash memory]], and one or more [[central processing unit|processors]], as well as two or more network interfaces. They come in a variety of sizes from something you could hold in your hand to something too large for one person to lift.
A '''router''' is a [[computer]] whose [[software]] and [[Computer hardware|hardware]] are designed to move data between [[Computer network|computer networks]]. Routers move traffic to where it needs to go. They do this by choosing the shortest path between the computers using a complicated system of rules called [[routing protocol]]s. Most routers have a specialized [[operating system]], [[random access memory|RAM]], [[NVRAM]], [[flash memory]], and one or more [[central processing unit|processors]]. They also have two or more [[network card|network interface]]s. They come in a variety of sizes from something that could hold in the hand to something too large for one person to lift.


If you have an internet connection, you probably have a router somewhere that your computer sends data to. This is the first router your computer will connect to in order to get to the internet. It is also known as a [[default gateway]] (because it is your gateway to the internet). By convention the gateway has the lowest [[IP address]] (like a phone number for a computer) in the [[subnet]] (a group of addresses). Anytime you make a connection (such as a connection to www.wikipedia.org) your computer looks up the IP address using the look-up service called [[Domain Name System|DNS]] (Domain Name Service). Once the destination address has been found your computer connects to your gateway router. The gateway then sends data to a router at your [[Internet service provider|ISP]] (Internet Service Provider), that router can be said to be part of the internet and connects to other routers until the data reaches the destination.
If a computer has an connection to the [[Internet]], It is connected to a router that the computer sends data to. This is the first router the computer will connect to in order to get to the internet. It is known as a [[default gateway]] because it is the gateway to the internet. By convention, the gateway has the lowest [[IP address]] (like a phone number for a computer) in the [[subnet]] (a group of addresses). Anytime a computer makes a connection (such as a connection to www.wikipedia.org), the IP address of the destination server is found using a service called [[Domain Name System|DNS]] ([[Domain Name System]]). Once the destination address has been found, the computer connects to the gateway router. The gateway then sends data to a router at the [[Internet service provider|ISP]] ([[Internet service provider|Internet Service Provider]]). That router is a part of the internet and connects to other routers until the data reaches the destination.
[[File:Belkin Wireless G Router F5D7231-4 Version 1000de-1121.jpg|left|thumb|Small router with WiFi built in.]]
[[File:Belkin Wireless G Router F5D7231-4 Version 1000de-1121.jpg|left|thumb|Small router with [[Wi-Fi|WiFi]] built in.]]
In small networks such as homes, small businesses (including [[internet café]]s) and small schools, the router also performs [[Network address translation|NAT]] (network address translation) which makes all outgoing connections look like they come from one address. Typically, incoming connections are only allowed if they are replies to connections made by a computer inside the NAT.
In small networks such as homes, small businesses (including [[internet café]]s) and small schools, the router also performs [[Network address translation|NAT]] (network address translation) which makes all outgoing connections look like they come from one address. Typically, incoming connections are only allowed if they are replies to connections made by a computer inside the NAT.


Routers connect two or more networks and direct traffic between them. These networks may be physical (the network is associated with a port) or logical (not associated with a port on the router).<ref>[ftp://ftp.rfc-editor.org/in-notes/rfc1812.txt Requirements for IPv4 Routers],RFC 1812, F. Baker,June 1995</ref> The term '''layer 3 switch''' often is used the same as 'router', but it is a general term without a technical definition. Layer 3 switch implies a device that is built to connect [[Ethernet]] devices in a [[LAN]] but can also perform routing.
Routers connect two or more networks and direct traffic between them. These networks may be physical (the network is associated with a port) or logical (not associated with a port on the router).<ref>[ftp://ftp.rfc-editor.org/in-notes/rfc1812.txt Requirements for IPv4 Routers],[[RFC:1812|RFC 1812]], F. Baker,June 1995</ref> The term '''layer 3 switch''' often is used the same as 'router', but it is a general term without a technical definition. Layer 3 switch implies a device that is built to connect [[Ethernet]] devices in a [[LAN]] but can also perform routing.


Router operating systems are split into two parts:<ref>[ftp://ftp.rfc-editor.org/in-notes/rfc3654.txt Requirements for Separation of IP Control and Forwarding],RFC 3654, H. Khosravi & T. Anderson,November 2003</ref>
Router operating systems are split into two parts:<ref>[rfc:3654 Requirements for Separation of IP Control and Forwarding],[[RFC:3654|RFC 3654]], H. Khosravi & T. Anderson,November 2003</ref>
* The [[Control Plane]], where the router learns the best port to send data to for a specific destination
* The [[Control Plane]], where the router learns the best port to send data to for a specific destination
* The [[Forwarding Plane]], where the router does the work of sending data to its destination.
* The [[Forwarding Plane]], where the router does the work of sending data to its destination.
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[[Category:Computer networking| ]]
[[Category:Computer networking| ]]
[[Category:Internet]]

Latest revision as of 18:37, 16 March 2024

Computers connected to a server using a router

A router is a computer whose software and hardware are designed to move data between computer networks. Routers move traffic to where it needs to go. They do this by choosing the shortest path between the computers using a complicated system of rules called routing protocols. Most routers have a specialized operating system, RAM, NVRAM, flash memory, and one or more processors. They also have two or more network interfaces. They come in a variety of sizes from something that could hold in the hand to something too large for one person to lift.

If a computer has an connection to the Internet, It is connected to a router that the computer sends data to. This is the first router the computer will connect to in order to get to the internet. It is known as a default gateway because it is the gateway to the internet. By convention, the gateway has the lowest IP address (like a phone number for a computer) in the subnet (a group of addresses). Anytime a computer makes a connection (such as a connection to www.wikipedia.org), the IP address of the destination server is found using a service called DNS (Domain Name System). Once the destination address has been found, the computer connects to the gateway router. The gateway then sends data to a router at the ISP (Internet Service Provider). That router is a part of the internet and connects to other routers until the data reaches the destination.

Small router with WiFi built in.

In small networks such as homes, small businesses (including internet cafés) and small schools, the router also performs NAT (network address translation) which makes all outgoing connections look like they come from one address. Typically, incoming connections are only allowed if they are replies to connections made by a computer inside the NAT.

Routers connect two or more networks and direct traffic between them. These networks may be physical (the network is associated with a port) or logical (not associated with a port on the router).[1] The term layer 3 switch often is used the same as 'router', but it is a general term without a technical definition. Layer 3 switch implies a device that is built to connect Ethernet devices in a LAN but can also perform routing.

Router operating systems are split into two parts:[2]

  • The Control Plane, where the router learns the best port to send data to for a specific destination
  • The Forwarding Plane, where the router does the work of sending data to its destination.

Related pages[change | change source]

References[change | change source]

  1. Requirements for IPv4 Routers,RFC 1812, F. Baker,June 1995
  2. [rfc:3654 Requirements for Separation of IP Control and Forwarding],RFC 3654, H. Khosravi & T. Anderson,November 2003