Local Area Network
A local area network (LAN) is a computer network confined to a small geographic area, such as a home, an office floor, a school or a single campus, in which the devices are linked by Ethernet cables, Wi-Fi or both and are typically owned and administered by one organization or household. The defining features are proximity and private ownership: because the links are short and belong to the same party, a LAN can offer high speed and very low delay without renting capacity from a carrier.
Ethernet and Wi-Fi are the two technologies that dominate LANs, and both are published IEEE standards. Ethernet, conceived by Robert Metcalfe at Xerox PARC in 1973, was standardized as IEEE 802.3 in 1983 and has since grown from 10 megabits per second on shared coaxial cable to 1, 10, 100 gigabits and beyond over twisted pair and fiber. Wi-Fi, based on IEEE 802.11 (first published in 1997), carries the same style of frames over radio, trading some speed and reliability for mobility. Both identify devices at the local level by a hardware address (the MAC address) burned into the network interface, and both deliver data as frames to other devices on the same segment, which is the job of the network switch, covered in its own entry.
A LAN usually forms a single broadcast domain, meaning that a message addressed to everyone is delivered to every device on it, and this shapes both its services and its limits. Protocols such as ARP, which asks which device owns a given IP address, and DHCP, which hands newly connected devices an address, rely on such local broadcasts. Home and office LANs commonly use private address ranges reserved by RFC 1918 (for example addresses beginning with 192.168 or 10), which are not routable on the public internet and are therefore reused in millions of separate LANs. Large LANs are divided into virtual LANs (VLANs, standardized as IEEE 802.1Q) so that, for example, guest Wi-Fi, office computers and security cameras are kept apart on the same physical equipment, limiting both broadcast traffic and the spread of any compromise.
The LAN ends at its gateway, the router that connects it to other networks, and that boundary is the key to understanding what a LAN is and is not. Traffic between two devices on the LAN never leaves it, so copying a large file to a local server runs at local link speed and keeps working when the internet connection fails. Traffic for any other destination is sent to the default gateway, which hands it on, translating private addresses into a public one through network address translation. The router and the wide area network beyond it each have separate entries. A related practical point is that a LAN is no longer purely a hardware concept: virtual networks in the cloud, container networks and VPNs imitate a LAN so that remote machines behave as if they sat on the same switch.
Common misconceptions are that Wi-Fi equals the internet, that a LAN requires internet access, and that devices inside a LAN are automatically safe. A Wi-Fi router can be fully working while the internet service is down, and local devices will keep talking to each other. Conversely, a LAN is a shared trust zone: anyone who joins, through a weak password or a compromised device, can often observe broadcast traffic and probe neighbors, which is why segmentation, strong WPA3 or WPA2 encryption and updated firmware matter. LANs remain essential where speed and latency are critical: offices and homes, data centers where servers connect through high-speed switches, and clusters of machines doing machine learning training that exchange gradients over dedicated, very fast local fabrics.
Read a local area network as the private, short-range neighborhood of a network: a handful of devices under one owner that talk directly through cables and radio at high speed, reach the wider world only through a gateway at the edge, and are therefore only as secure as their weakest member.