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I am a beginner and currently learning network devices and I got a little stuck on switches.

Basically, what I've learned is that they connect/provide a wired connection between computers on the same LAN and allow them to communicate with each other.

What exactly is meant by "communicate"? Like share a file, for example? If I didn't have computers connected to a switch, would they still be able to communicate through Wi-Fi, for example? Thank you all in advance.

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Basically, it means they are able to send packets.

This can be done with cables and a working switch, or via Wireless, i.e. over and Access Point, or in direct Ad-Hoc mode. This is the physical link establishment. You get working physical link (wired or wireless) on which your device can send and receive electrical or radio signals.

File sharing and other stuff you do come later as services. One computer acts as a file server, sharing over SMB, FTP, HTTP or similar protocols, and the other as client. So, when connected there is no limit on what you can do with it, unless you set restrictions in switch or in firewall on the operating system.

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  • Thank you very much for the explanation. So if I, for example, send a skype message to a device on the same network, I will send a packet to it? And if I have no Wireless or a switch (Wired connection), only those PCs that are directly connected to the router and to the internet would be able to communicate?
    – Mitrixsen
    Jan 27, 2022 at 10:50
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    @Mitrixsen Skype centralizes on a server that enables all communication - a client always sends its data to the (remote) server and the other client receives data from the server, even when the clients are just a meter apart.
    – Zac67 ♦
    Jan 27, 2022 at 11:53
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    @Mitrixsen When you use Skype and any other internet service/app outside your local network, the traffic goes through switch to router (or modem which is a router as well) to internet and back to other local device. There is no "only" whatsoever. Everything is connected. You either use local service of another computer (e.g. file sharing) or cloud services on the internet. The traffic of the former stays inside your local network, while the latter's goes out and comes back in.
    – MTG
    Jan 30, 2022 at 7:07
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A switch is the major network device enabling communication on the data link layer (L2) in the OSI networking model. Usually, "switch" refers to an Ethernet switch.

Basically, nodes in the connected network can send network packets (frames in correct jargon) to each other that are addressed to their hardware addresses. Each frame carries a marker (EtherType) indicating for which "upper-layer" protocol it transports data.

Commonly, that upper-layer protocol may be an IP protocol (in OSI's network layer L3) that enables communication between nodes in different L2 networks using routers as gateways.

On top of IP sits a transport-layer protocol (L4) that enables communication between applications - e.g. a web browser and a web server.

These then speak a common application-layer protocol (L7) - SMB, FTP, HTTP, .... - that allows them to actually exchange data.

From the architecture POV, a switch is multi-port bridge, just like a wireless access point that interconnects a wireless LAN. These work somewhat differently than a switch, but their general purpose is the same.

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There are 2 type switches in networking world ..

  1. unmanaged switches
  2. managed switches

Unmanaged switches : Are just like plug and play .. where frame are forwarded , it works on data link layer . Mac address table is used to forward frames on respective switch interface ..

Managed switches are again divided in two types L2 switch and L3 switch

L2 switch works on data link layer of OSL model . Mac address table is used as reference to forward frames on switch ports ..

//Mac address table maps//

Mac address ---> switch ports

L3 switch works on both data link and network link of OSI model

Arp table and Mac address table and routing tables are used as reference to forward packet to destination.

Switch allows ipv4 ,ipV6 , UDP & TCP , unicast , multicast traffic throught it .

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