What is LAN?

LAN (Local Area Network) is a local computer network, that is, a network that covers a limited area: a room, apartment, office, building, or campus.

Short phrasing for the interview:

LAN is a local network that connects devices within a small area using wired and/or wireless technologies for fast data exchange and shared use of resources.

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#Main features of LAN

#1. Limited area

LAN typically covers:

• an apartment
• an office
• a floor
• a classroom
• a group of campus buildings

LAN does not stretch across a city or a country - that would already be MAN/WAN.

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#2. High speed

LAN is the fastest category of networks. Typical speeds:

• Ethernet 1 Gbit/s
• 2.5G / 5G / 10G Ethernet
• Wi-Fi 5/6/6E/7 - hundreds of Mbit/s up to several Gbit/s

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#3. Low latency

Latency between devices in the same LAN is milliseconds or less. This matters for:

• streaming
• online games
• VoIP
• file servers

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#4. Main LAN technologies

#Wired:

• Ethernet (the most common standard)
• fiber-optic Ethernet in data centers

#Wireless:

• Wi-Fi (WLAN - a subtype of LAN)

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#5. LAN network equipment

A typical set:

• Switches - the backbone of wired LAN
• Router - connects LAN to the internet (WAN)
• Wi-Fi access points (AP)
• Cabling infrastructure - twisted pair (Cat5e/6/6a/7/8), fiber

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#Tasks LAN solves

1. Data exchange between devices (packets, files, requests).
2. Shared access to resources:

• files (NAS, file server)
• printers
• internet connection

3. Interaction of services within an organization:

• a database
• web services
• domain policies

4. Centralized device management:

• updates
• monitoring
• security

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#LAN in real life

#LAN examples:

• Home network: router, laptops, phones, Smart TV.
• Office network: dozens of PCs + server room + printers + Wi-Fi access points.
• University campus: several buildings connected by fiber.

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#Important terms related to LAN

• LAN Segment - a part of a network joined by a switch.
• Broadcast domain - the area in which a broadcast request is seen by everyone.
• VLAN - a logical division of a LAN into isolated virtual networks.

These terms come up often in interviews.

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#Ready answer for the interview (short and clear)

LAN is a local network that operates within a limited area (home, office, campus). It mainly uses Ethernet and Wi-Fi, provides high speed and low latency, and lets devices within that area exchange data and share resources.

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#Cheat sheet (5 seconds before the interview)

• LAN = Local Area Network.
• Limited area.
• High speeds (Ethernet / Wi-Fi).
• Switches, access points, router.
• Data exchange and shared access to resources.