Azure Virtual Network Basics

Key Takeaway: Azure Virtual Network (VNet) is the fundamental building block for your private network in Azure. It enables you to securely connect Azure resources to each other, to the internet, and to your on-premises networks.

An Azure Virtual Network (VNet) is a logical representation of your network that you create in Azure. It's a flat address space that is assigned to your subscription. You can then divide this address space into subnets. Each VNet is isolated from all other VNets in Azure, which gives you control over traffic flow and security.

What is a Virtual Network?

A VNet provides the following core capabilities:

Resource Isolation: VNets provide a private, isolated network space for your Azure resources, such as virtual machines, web apps, and databases.
Subnetting: You can segment your VNet into smaller IP address ranges called subnets. This helps in organizing resources and implementing granular security policies.
Traffic Routing: Azure automatically routes traffic between subnets within a VNet. You can also configure custom routes to control traffic flow.
Connectivity: VNets can connect to other VNets (VNet peering), to your on-premises networks (VPN Gateway or ExpressRoute), and to the internet.
Security: You can implement network security groups (NSGs) and Azure Firewall to control inbound and outbound traffic to your resources.

Key Components of a Virtual Network

When you create a VNet, you'll define several key components:

Address Space

The private IP address range for your VNet, expressed in CIDR notation (e.g., 10.0.0.0/16). This defines the total pool of IP addresses available within your VNet.

Subnets

Segments of the VNet's address space. Each subnet can host specific Azure resources. Subnet IP ranges must be within the VNet's address space and cannot overlap.

Network Security Groups (NSGs)

Virtual firewalls that allow or deny network traffic to resources connected to an Azure VNet. You can define rules based on source/destination IP address, port, and protocol.

Route Tables

Used to override Azure's default system routes. You can define custom routes to control how traffic is routed between subnets, to the internet, or to your on-premises networks.

Common Use Cases

Azure Virtual Networks are essential for a wide range of cloud deployments:

Hosting IaaS Workloads: Securely deploy and connect your virtual machines and other IaaS resources.
Hybrid Cloud Connectivity: Extend your on-premises network to Azure, allowing seamless communication between your local and cloud resources.
Microservices Architectures: Isolate and connect different tiers or services of your application using subnets and NSGs.
Disaster Recovery: Create a mirrored network environment in Azure for business continuity.

Getting Started

You can create and manage VNets through the Azure portal, Azure CLI, PowerShell, or ARM templates.

To learn more, explore the following resources:

Next Steps

Now that you understand the basics of Azure Virtual Networks, you can explore topics like:

Azure Load Balancer for distributing traffic
Azure Firewall for advanced threat protection
Azure VPN Gateway for connecting to on-premises networks