Editing Router (computing) (section)

{{short description|Device that forwards data packets between computer networks}}
{{About|the network device||Router (disambiguation)}}
{{Merge from|Wireless router|date=December 2024|discuss=Talk:Router (computing)#Merge}}
{{Use American English|date=June 2020}}

{{Multiple image
| image1            = ASR9006.jpg
| caption1          = Rack containing a service-provider–class router connected to multiple networks
| image2            = SpeedStream 6520 Derrière.JPG
| caption2          = A home–class router with wireless capabilities; many home routers like this example combine router, [[wireless access point]], [[network switch|switch]] and [[modem]] into one single unit (see also [[residential gateway]])
}}

A '''router'''{{efn|Pronounced {{IPAc-en|ˈ|r|uː|t|ər}} in [[British English]], {{IPAc-en|ˈ|r|aʊ|t|ər}} in [[American English|American]] and [[Australian English]].<ref>{{OED|router}}</ref>}} is a [[computer]] and [[networking device]] that [[Packet forwarding|forwards]] [[data packet]]s between [[computer network]]s, including [[internetworks]] such as the global [[Internet]].<ref>{{cite web |title=A Router is a Computer |url=http://cisco.num.edu.mn/CCNA_R&S1/course/module6/6.3.1.1/6.3.1.1.html |archive-url=https://web.archive.org/web/20220705091357/http://cisco.num.edu.mn/CCNA_R&S1/course/module6/6.3.1.1/6.3.1.1.html |archive-date=2022-07-05 |website=Cisco Network Academy}}</ref><ref name="Medhi">{{cite book
 | last1  = Medhi
 | first1 = Deepankar
 | last2  = Ramasamy
 | first2 = Karthik
 | title  = Network Routing: Algorithms, Protocols, and Architectures
 | publisher = Elsevier
 | date   = 2007
 | pages  = 19
 | language = 
 | url    = https://books.google.com/books?id=IM-Y2W0RIF0C&dq=%22router+is+a+specialized+computer%22&pg=PA19
 | doi    = 
 | id     = 
 | isbn   = 9780120885886
 }}</ref><ref name="Kundu">{{cite book
 | last1  = Kundu
 | first1 = Sudakshina
 | title  = Fundamentals of Computer Networks, 2nd Ed.
 | publisher = PHI Learning
 | date   = 2009
 | location = New Delhi
 | pages  = 85–86, 124
 | language = 
 | url    = https://books.google.com/books?id=OMoHmEQHosAC&q=router%20is%20a
 | doi    = 
 | id     = 
 | isbn   = 9788120334526
 }}</ref>

Routers perform the "traffic directing" functions on the Internet.  A router is connected to two or more data lines from different [[IP network]]s. When a data packet comes in on a line, the router reads the [[network address]] information in the packet header to determine the ultimate destination. Then, using information in its [[routing table]] or [[routing policy]], it directs the packet to the next network on its journey. Data packets are forwarded from one router to another through an [[internetwork]] until it reaches its destination [[Node (networking)|node]].<ref>{{cite web|url=http://www.tcpipguide.com/free/t_OverviewOfKeyRoutingProtocolConceptsArchitecturesP.htm|title=Overview Of Key Routing Protocol Concepts: Architectures, Protocol Types, Algorithms and Metrics|publisher=Tcpipguide.com|access-date=15 January 2011|url-status=live|archive-url=https://web.archive.org/web/20101220111345/http://tcpipguide.com/free/t_OverviewOfKeyRoutingProtocolConceptsArchitecturesP.htm|archive-date=20 December 2010}}</ref>

The most familiar type of [[Internet Protocol|IP]] routers are [[Residential gateway|home and small office routers]] that forward [[IP packet (disambiguation)|IP packet]]s<!--intentional link to disambig, could be either IPv4 or IPv6 packet--> between the home computers and the Internet. More sophisticated routers, such as enterprise routers, connect large business or ISP networks to powerful [[core router]]s that forward data at high speed along the [[optical fiber]] lines of the [[Internet backbone]].

Routers can be built from standard computer parts but are mostly [[embedded system|specialized purpose-built computers]]. Early routers used [[software]]-based forwarding, running on a [[CPU]]. More sophisticated devices use [[application-specific integrated circuit]]s (ASICs) to increase performance or add advanced filtering and [[Firewall (computing)|firewall]] functionality.