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Network segment

(also subnet)

Network segment definition

A network segment is an isolated or separated part of a computer network. Network segmentation is usually accomplished by using routers, switches, or firewalls. Devices in any given network segment can communicate with each other without going through a router, but reaching other segments requires routing or bridging.

See also: network access control, network bottleneck, network infrastructure, network security protocols, lateral movement, cyberthreat

Reasons for network segmentation

  • Security: Network segmentation can reduce the attack surface of a network by isolating sensitive or critical systems. Placing security barriers between different network segments prevents lateral movement (the gradual infiltration of a network from one compromised endpoint) and blocks many insider threats (such as disgruntled employees sabotaging key systems). This is particularly important for organizations operating in the fields of finance, healthcare, and government.
  • Performance: Network segmentation can help manage network traffic and reduce congestion.
  • Management: Breaking down a network into smaller segments makes it easier to monitor, control, repair, and upgrade.
  • Compliance: Some industries (like healthcare and finance) have strict regulatory requirements for data privacy and security. By providing an additional layer of protection for sensitive data, network segmentation helps organizations meet their legal obligations and protect user information.
  • Guest access: Network segmentation lets organizations offer Wi-Fi services to guests (such as visitors to the premises or hired contractors) without exposing sensitive parts of the network. Guest segments only offer access to the internet (for example, if the user wants to check their email) without connecting to network devices or servers.