This post by David Papkin about Virtual Networks using Microsoft Azure
Virtual Networks (VNets) in Microsoft Azure are network overlays that you can use to configure and control connectivity between virtual machines (VMs) and PaaS cloud service roles. You can use both VMs and PaaS cloud services without VNets but, when you organize them into VNets, you enable them to communicate directly on an isolated network and can set IP addressing schemes and name resolution settings.
Virtual networks (VNets) in Windows Azure also enable you to extend your on-premises networks into the cloud. To build such a configuration, you must connect a Virtual Private Network (VPN) from your on-premises computers or networks to the Azure VNet. Alternatively, you can use ExpressRoute to provide a connection to an Azure VNet that does not cross the Internet. In this way, you can enable on-premises users to access Azure services as if they were physically located on-premises in your own datacenter. VNets are often used to support Virtual Machines (VMs) by grouping them into subnets. However, you can also create PaaS Cloud Services in VNets for the same reason.
Implementing and Managing Virtual Networks
To create a virtual network, you can either use the full portal or upload a network configuration file. A network configuration file is an XML file with a specific schema.
IMplementing Virtual Networks using Microsoft Azure by David Papkin Demo
This concludes this post by David Papkin about Virtual Networks using Microsoft Azure
To learn more about using Microsoft Azure, the following Microsoft course 20533 is available