Virtual network provides an isolated and secure environment to run your VMs and applications. You can bring your private IP addresses, define subnets, access control policies and much more. With virtual networks, you get to treat Azure just as your own datacenter.
Within a virtual network, you can choose to run a variety of network virtual appliances (WAN optimizers, load balancers, Application Firewalls etc.,) and define how traffic flows allowing you to design the network with a greater degree of control.
With Azure Virtual Network you can easily extend your on-premises IT environment into the cloud, much the way you can set up and connect to a remote branch office. You can choose to connect using an IPSEC VPN or via a private connection using the ExpressRoute service. You have multiple options to securely connect to a Virtual Network – you can choose an IPSEC VPN or a private connection using the ExpressRoute service.
With Virtual Network, you can build hybrid cloud applications that securely connect to your on-premises datacenter—so an Azure web application can access an on-premises SQL Server database or authenticate users against an on-premises Active Directory service.
With virtual networks, you can build services that rely on Cloud Services and Virtual Machines. Use Azure web roles for your front end and Virtual Machines for backend databases. Combining Platform-as-a-Service (PaaS) and Infrastructure-as-a-Service (IaaS) within a Virtual Network gives you more flexibility and scalability in building apps.