how do I count LANs and WANs given a network topology? The question is quite straightforward. I find it difficult to know when something is a LAN or when it isn't. Same goes for WAN.

Here's an example where I would like to count the LANs and WANs.

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1 Answer 1


As per wikipedia, LANs:

"A local area network (LAN) is a computer network that interconnects computers within a limited area such as a home, school, computer laboratory, or office building, using network media.[1] The defining characteristics of LANs, in contrast to wide area networks (WANs), include their smaller geographic area, and non-inclusion of leased telecommunication lines."

I would add that Cisco Academy describes LANs similar to the above but also as controlled by by a single organization (i.e. one business, one school, one government department).

and for WANs, wikipedia says:

"A wide area network (WAN) is a network that covers a broad area (i.e., any telecommunications network that links across metropolitan, regional, national or international boundaries) using leased telecommunication lines."

In practice you can usually identify WANs in diagrams by clouds or lightning bolt-like connections (WAN links). LANs are then the groups of switches and end-user devices that separated by the WAN links. Usually routers are used to separate LANs. So for the given diagram, 2 LANs and one WAN (WAN implied by the WAN link).

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