From what you have learned so far in Azure, you must know that Azure is a very flexible and customizable platform, and that applies to all its services, including networking services.
In a nutshell, the isolation that Azure provides to the virtual networks does not mean you cannot build your own routes to other virtual networks, or span your networking across on-premises and Azure.
Earlier, in Chapter 2, Delving into Azure Virtual Networks, you learned how to do VNet peering. Throughout this chapter, you will learn new and more ways to customize Azure networking, that includes, VNet2VNet connection, Point-to-Site connection, Site-to-Site connection, ExpressRoute, and user-defined routing.
In one sentence, ...