Thoughts on what is a LAN?

[LetMePass]

Hi people,

If you were interviewed for a job in Networking, what would you answer to the question "What is a LAN?"

https://www.cisco.com/c/en/us/products/switches/what-is-a-lan-local-area-network.html

Cisco definition:

A local area network (LAN) is a collection of devices connected together in one physical location, such as a building, office, or home. A LAN can be small or large, ranging from a home network with one user to an enterprise network with thousands of users and devices in an office or school.

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Regardless of size, a LAN's single defining characteristic is that it connects devices that are in a single, limited area.

A LAN comprises cables, access points, switches, routers, and other components that enable devices to connect to internal servers, web servers, and other LANs via wide area networks.

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Here is the debate. It's a local area network. It's a limited area. Routers enable communications across networks (also read router is necessary for BIG LAN but anyway, and it came to me that most of software today works with IP so even a LAN will require router). How a LAN is a really LAN if a router is involved? Router = IP? What is a purpose to have a device that enables communications across network if LAN is supposed to be isolated? No IP = No ARP? In a LAN if I follow OSI model, a frame is just a packet with L2 header..

What would be a good answer to the question "What is a LAN"?

Can I build a LAN with an unmanaged switch and ten computers?

To me, no router, no ARP needed because absence of the need of IP but today LAN looks like an internal network that has some connection to the Internet.

What was a LAN 30 years ago?

[M02@rt37]

Hello @LetMePass 

A LAN is a network that connects devices within a limited geographical area such as a home, office, or campus. The primary purpose of a LAN is to enable the sharing of resources and information among interconnected devices. LANs are restricted to a small physical area, typically a single building or a group of closely located buildings, and comprise networking hardware like cables, switches, access points, and sometimes routers to facilitate communication and resource sharing. Historically, LANs did not necessarily require IP addressing or routers, as they were confined to layer 2 communications using MAC addresses. However, modern LANs often incorporate IP addressing and routing to support scalability, interconnectivity, and the functionality required by contemporary applications and services.

You can build a LAN with an unmanaged switch and ten computers, allowing them to communicate within the same local network segment without the need for a router. However, without a router, the network will lack the ability to route traffic between different subnets or connect to external networks. Thirty years ago, LANs were simpler and often operated without IP addressing, using technologies like Ethernet over coaxial cables and communicating primarily through layer 2 protocols, with routers primarily used to connect different LANs or to connect LANs to WANs. In contrast, modern LANs integrate IP addressing and often include routers to facilitate communication between different subnets within the same LAN, provide Internet access, and enable advanced services such as DHCP and DNS.

A LAN is a local network designed to interconnect devices within a limited area for resource sharing and communication, with modern LANs including advanced networking functions and connectivity.

[Ramblin Tech]

The definition of a "LAN" is a matter of perspective. For some PC users 30 years ago, the LAN was the Novell Netware server that they used to share files and printers. For others like me, who connected the PCs and servers together, the LAN was the cabling, repeaters, bridges, and routers that connected them.

What is the IEEE's perspective? After all, they have been standardizing LAN technologies for over 40 years (since February of 1980 to be precise). IEEE 802-2001 definition (I lost my hardcopies of the original 802 publications long ago):

LAN: A computer network, located on a user’s premises, within a limited geographical area.

The definition has not changed much in the latest (802-2014) version:

local area network (LAN): A network of devices, whether indoors or outdoors, covering a limited geographic area, e.g., a building or campus.

In both the 2001 and 2014 editions, the IEEE differentiates between IEEE LANs and generic LANs, with the former specifically using MAC protocols defined by IEEE 802. But in none of their 802 Section 3 definitions of LANs does the IEEE mention exclusive use of L2 addressing, interconnections made only with bridges vs routers, nor any connections to the Internet.

Keep it simple: A network of devices, whether indoors or outdoors, covering a limited geographic area, e.g., a building or campus.

[Maren Mahoney]

To answer your specific question, if I were giving an interview and asked "What is a LAN", and the person I was interviewing came back with the definitions and questions in your original post, I would hire them on the spot.

Answering with the above shows that you understand networking.

Maren