IP tunnel in many-to-many mode (virtual interface)?

Question

linux

I don't know if the title is a good question. Nothing better came to mind.
I have N servers, they are all connected to each other via the internet. It is necessary to organize a certain virtual interface (one on each server) and place them all on the same network. So that all computers think that they are connected to one big switch and stand next to each other.
I immediately discard the option with a centralized system, because. the amount of data that the servers will exchange is large enough.
The problem could be solved, for example, like this:

1. Connect a separate link to each server
2. Place all these connections in a separate vlan
, alas, this option will not work, the servers are far away, in different companies,
I would like a virtual interface.

In theory, I can create a separate ip-ip tunnel for each pair of servers. But when adding a server, the number of tunnels will increase by N-1. You can add tunnels not by hand, but through scripts, but this is some kind of wrong way.
Maybe there are solutions in the direction of which it is worth digging?
I would like it to be simple, transparent and understandable.
Theory:

You may have to create a solution on your own, the task is simple, we look at what came to the tun / tap interface, if the destination address is known to us in advance and defined in the config, then we simply send this data somewhere in the form of a udp packet. At the other end, everything that came to a specific udp port is dumped into a similar interface.

If this can be done (and it seems simple to me), then maybe there is already a ready-made solution?

Answer 1

linux-ip.net/gl/ip-tunnels/node9.html Is
it?
Only separately it will be necessary to think about tunnel encryption.

Answer 2

The task of combining computers into a virtual private network is solved by vpn server.
I personally recommend openVPN

Answer 3

“I immediately discard the option with a centralized system, because. the amount of data that the servers will exchange is large enough. „
If the servers will exchange peer-to-peer (P2P), then it is possible with a centralized system.
When using the neorouter.com/products.html solution, the traffic to the central server was ~ 7-10 Kbps, when copying files between servers at a speed of ~ 20 Mbps.
IMHO: SSLv3 (AES-256) encryption is more than enough for me.

Answer 4

GNU Virtual Private Ethernet is what you need.