What is used for VPN in practice?

Question

VPN

I'm interested in the use of VPN in work and corporate networks. And connecting remotely to such networks.
In theory, with VPN it seems clear.
But what is used in practice and how to study it, I do not know.
For example, ask me to connect two offices via vpn and nothing will come to my mind. I don't know technology. I know there are different protocols for creating a VPN, but this is all theory.

Answer 1

Well, it depends.
It is possible to raise vpn on simple routers and on tsiska and on Linux and on Windows and cross-platform.
It depends on what is already there, what is the budget, what are the requirements for stability and security.
Maybe there is no need for vpn.

Answer 2

Studying a catalog of bicycle parts or even disassembling and assembling a bicycle will not form the skill of riding it. Building a VPN is a technology. What to take, where to adjust, what to enter where. It is enough to do it once - and the next time it is done automatically. This is not the end goal. Of course the goal could be "synchronization between the branch DC and the office DC" and a VPN is just a tool to do that.
The bridge example in SyavaSyava 's answer is great.

Answer 3

I'm interested in the use of VPN in work and corporate networks. And connecting remotely to such networks.
In our office (a large insurance company included in the TOP-10), it looks something like this: there is a main office where the data center is located, and there are branches that are connected to this main office "via VPN". Technically, we configure IPSec on the one hand, IPSec on the other hand, and that's it. Between the two offices there is encrypted traffic on the public Internet. Other remote offices are connected in the same way.
There are also remote employees who connect to the main office using software VPN clients.
The whole thing is configured on the central router / firewall.
There are several types, above I talked about LAN-2-LAN (IPSec).