How to safely separate local networks?

Question

Computer networks

There are three computers that are already on the local network, which has a total of 50 machines. We now need to combine these three computers into our own local network, so that only they have access to the http server raised on one of them and to the shared folder on it.

Question: how to make this small local network so that it is reinforced concrete to be sure that users of a large network will not have access to it (to the http server and to the shared folder)? Moreover, these three machines must continue to have access to a large network.

All machines have Win XP.

I'm sure the question will be simple for many. I haven't worked with networks much. I would like to hear proven solutions.

Answer 1

Allocate a separate vlan to three machines, and run tagged traffic on them with a large network and a small one. In order to prevent access to the shared folder, deactivate the corresponding service on the vlan of a large network. Make the web server listen only on the interface from the small network.

Answer 2

Can't you just use a firewall on the http server?

Answer 3

One network connection? Static settings, without binding to mac?
You can additionally, by alias, issue settings, in addition to the main ones, from a different subnet, restrict connections by a firewall. It makes sense, of course, to transfer to another VLAN.
Another thing is that it is not clear through what equipment these computers are connected to the network.
Or use specialized software with access to the folder, at least with a password and, possibly, with binding to the same ip and mac.
[upd] I mean, the organization and topology of the network is not fully understood, this solution may vary.