MSDN Documentation

Introduction to Virtual Networks

Welcome to the introductory guide to virtual networks. This article provides a foundational understanding of what virtual networks are, their core concepts, and their importance in modern computing environments.

What is a Virtual Network?

A virtual network (VNet) is a logically isolated network that you can create within a public cloud provider's infrastructure. It allows you to define your own private IP address space, subnets, route tables, network gateways, and network security groups. VNets are the fundamental building blocks for your cloud deployments, enabling secure and private communication between your cloud resources.

Think of a virtual network as your own private network, but hosted on the internet. It provides the same benefits as a traditional on-premises network, such as IP addressing, subnets, routing, and network security, but with the flexibility and scalability of the cloud.

Key Concepts

• IP Addressing: VNets allow you to assign private IP addresses to your resources, ensuring that they are only accessible within your virtual network or through controlled connections.
• Subnetting: You can divide your VNet's IP address space into smaller segments called subnets. This helps in organizing resources and applying granular security policies.
• Routing: VNets define how traffic is routed between subnets, to the internet, and to your on-premises networks.
• Network Security Groups (NSGs): NSGs act as a distributed firewall that you can associate with subnets or individual network interfaces. They allow you to control inbound and outbound traffic based on rules.
• Gateways: Virtual network gateways enable connectivity between your VNets and other networks, such as your on-premises data centers (VPN Gateway) or other VNets (VNet-to-VNet connection).

Why Use Virtual Networks?

Virtual networks are essential for several reasons:

• Isolation and Security: VNets provide a secure, isolated environment for your applications and data, protecting them from unauthorized access.
• Scalability and Flexibility: Easily scale your network resources up or down as your needs change, without the need for physical hardware.
• Hybrid Connectivity: Seamlessly integrate your cloud resources with your existing on-premises infrastructure, creating a hybrid cloud environment.
• Resource Management: Organize and manage your cloud resources effectively using subnets and IP addressing schemes.
• Customization: Design your network topology to meet specific application requirements, control traffic flow, and enforce security policies.

Example Scenario

Imagine you are deploying a web application in the cloud. You would typically use a virtual network to:

1. Define a private IP address space for your application.
2. Create multiple subnets for different tiers of your application (e.g., a subnet for web servers, a subnet for databases).
3. Configure Network Security Groups to allow traffic only to the web server subnet on specific ports (e.g., HTTP/HTTPS) and restrict direct access to the database subnet from the internet.
4. Use a public IP address for your load balancer or web servers to make them accessible from the internet.

For more detailed information on specific networking features, please refer to the Virtual Networks Deep Dive article.