How is the network built in the institution?

Question

Computer networks

Hello!
I ask for help in admin matters.
I am a programmer, the other day I came to my uncle in a cafe and became interested in the technology for implementing the home page of dom.ru when connected to wifi (who doesn’t know: dom.ru offers to choose one of the options when entering any resource - you are a subscriber or a guest. If a guest, then they give you 1 megabit of speed, and if you choose a subscriber and enter the contract number and phone number, then you get the same speed as your tariff plan).
The first thought is that this is a captive portal and the router is flashed, for example, dd-wrt.
But they have a wifi transmitter that includes a simple twisted pair with PoE.
After following the direction of the cable, I found a switch that the housebreakers fitted:

Here, port number # 2 is a twisted pair that goes to the wifi adapter.
but what is cable #4? It turns out that this is a fast Internet for office workers without ads and other speed limits.
Unfortunately, I'm not well versed in network technologies and, for the sake of interest, I swapped cables. As a result, the Internet did not work either in the "office" part, or for cafe visitors through a wifi adapter.
I believe that every programmer should understand related technologies at least at a basic level, so I will try to formulate the question:
How does dom.ru do all this? Why is the connector number so important and if they are swapped, nothing works?

Answer 1

Hey! Most likely, the switch ports are bound to the poppy address, so the change did not work, in addition (more precisely, even more likely) there may well be a vlan on the wifi port, so you can’t get traffic from it just by connecting, as well as giving the usual Internet (any) to the access point, tk. the point is waiting at the entrance as vlan.
Among other things, it is quite possible that the office and Wi-Fi have different ip addresses of the networks, so if you give the necessary vlan to the Wi-Fi point, it may well not see anything, since its default gateway is simply not available (and hence the expected page authorization \ radius server too), because Wi-Fi also falls off.
In other words, even if they wanted to specifically create such a scheme in which replacing the cable would make the Wi-Fi and the network work (but vice versa), they most likely would not have succeeded.

Answer 2

It's simple - port 2 and 4 are different vlans. On the second, the usual Internet (possibly with a static IP), on the fourth, the vlan goes to the provider's network so that the point can log in (so that no one sticks the left point) and give the desired page to the clients. Accordingly, in order for you to start after changing ports, you need to reconfigure the point and the computer)

Answer 3

There is absolutely nothing complicated here. Let's start in order. The blue cable goes to the provider's network, everything is clear here. Cable number 2 goes to the access point and (ATTENTION) it carries power to the POE. Cable number 4 goes (where by the way does it go?), but I will assume that it is in the switch. So that’s why the network doesn’t work for you if you swap everything, and everything is simple, you pulled out the cable from the power supply from the access point, accordingly, it fell without power, and sent PoE to another switch for employees, which naturally put it down (it’s good that they didn’t burn ).
The access point itself works through a tunnel to the provider’s controller (without knowing what kind of vendor I won’t say what kind of controller, but the essence is the same everywhere) and any connection to it goes through this controller, which is responsible for entering the password, advertising, etc.