In a typical small to medium business, using Linux as a router has a number of advantages, including low cost and flexibility; also, a Linux router can be used to do a lot more than just routing.
Let's analyze the following example of a typical small to medium company:
The network above is built for a small to medium company with sales, accounting, executive, and IT departments as illustrated in the diagram.
For easy understanding of the network, we've placed three switches belonging to three separate networks, one for the sales and accounting departments, one for the executive offices, and one for the IT department. Usually, a managed switch is used in this case to create three separate VLANS.
What we have here in this network is: