How to separate an Internet network from a regular network?

Question

Computer networks

Such a question: there is a network with computers that do not need to go online and there is a network with the Internet on which I go online how to make it possible to surf the Internet and steer remotely computers on the network without running to the object by poking lan laces. To make it clearer, I will attach an image Help me solve the problem.

Answer 1

karinko milipizdria. magnifying glass as a gift? solves easily with any router by prohibiting certain devices from going to this very Internet.