# Network segment

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{{Short description|Portion of a computer network}}
{{Use American English|date = March 2019}}
{{Use dmy dates|date=May 2025}}

A '''network segment''' is a portion of a [computer network](/source/computer_network). The nature and extent of a segment depends on the nature of the network and the device or devices used to interconnect end stations.<ref>{{cite web |url=http://www.linfo.org/network_segment.html |title=Network Segment Definition |date=2 October 2005 |access-date=2010-09-03 |archive-date=7 June 2023 |archive-url=https://web.archive.org/web/20230607181215/http://www.linfo.org/network_segment.html |url-status=live }}</ref>

==Ethernet==
According to the defining [IEEE 802.3](/source/IEEE_802.3) standards for [Ethernet](/source/Ethernet), a network segment is an ''electrical connection'' between networked devices using a [shared medium](/source/shared_medium).<ref>{{citation |section=1.4.318 |quote=segment: The medium connection, including connectors, between Medium Dependent Interfaces (MDIs) in a CSMA/CD local area network. |publisher=IEEE |title=802.3-2008 Part 3: Carrier sense multiple access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications |date=26 December 2008}}</ref> In the original [10BASE5](/source/10BASE5) and [10BASE2](/source/10BASE2) Ethernet varieties, a segment would therefore correspond to a single coax cable and all devices tapped into it. At this point in the evolution of Ethernet, multiple network segments could be connected with [repeater](/source/repeater)s (in accordance with the [5-4-3 rule](/source/5-4-3_rule) for 10 Mbit Ethernet) to form a larger [collision domain](/source/collision_domain).

With [twisted-pair Ethernet](/source/twisted-pair_Ethernet), electrical segments can be joined using repeaters or [repeater hub](/source/repeater_hub)s, as can other varieties of Ethernet. This corresponds to the extent of an [OSI layer 1](/source/OSI_layer_1) network and is equivalent to the collision domain.<ref>{{cite web |url=http://www.linktionary.com/s/segment.html |title=Segment (Network) |access-date=2010-09-03 |archive-date=20 December 2010 |archive-url=https://web.archive.org/web/20101220021727/http://linktionary.com/s/segment.html |url-status=live }}</ref><ref>{{cite web |url=http://compnetworking.about.com/od/networkdesign/l/bldef_segment.htm |title=Segment |access-date=2010-09-03 |archive-date=5 December 2010 |archive-url=https://web.archive.org/web/20101205231324/http://compnetworking.about.com/od/networkdesign/l/bldef_segment.htm |url-status=dead }}</ref> The 5-4-3 rule applies to this collision domain.

Using [switches](/source/network_switch) or [bridges](/source/network_bridge), multiple layer-1 segments can be combined to a common [layer-2](/source/layer-2) segment, i.e. all [nodes](/source/node_(networking)) can communicate with each other through [MAC address](/source/MAC_address)ing or [broadcasts](/source/broadcasting_(networking)). A layer-2 segment is equivalent to a [broadcast domain](/source/broadcast_domain). Traffic within a layer-2 segment can be separated into virtually distinct partitions by using [VLAN](/source/VLAN)s. Each VLAN forms its own logical layer-2 segment.

==IP==
A [layer-3](/source/layer-3) segment in an [IP network](/source/IP_network) is called a [subnetwork](/source/subnetwork), formed by all nodes sharing the same network prefix as defined by their IP addresses and the network mask.<ref>{{cite web |url=http://www.inetdaemon.com/tutorials/networking/lan/define_network_segment.shtml |title=What is a Network Segment? |access-date=2010-09-03 |archive-date=19 January 2012 |archive-url=https://web.archive.org/web/20120119144752/http://www.inetdaemon.com/tutorials/networking/lan/define_network_segment.shtml |url-status=live }}</ref> Communication between layer-3 subnets requires a [router](/source/router_(computing)). Hosts on a subnet communicate directly using the layer-2 segment that connects them. Most often, a subnetwork corresponds exactly with the underlying layer-2 segment, but it is also possible to run multiple subnets on a single layer-2 segment.

==References==
{{reflist}}

{{DEFAULTSORT:Network Segment}}
Category:Ethernet
Category:Network architecture

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Adapted from the Wikipedia article [Network segment](https://en.wikipedia.org/wiki/Network_segment) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Network_segment?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.