Microsoft Azure Virtual Network Explained

Azure Virtual Network (VNet) is the fundamental building block for private networking in Azure. It enables Azure resources like VMs to securely communicate with each other, the internet, and on-premises networks.

Core Components of a Virtual Network

• Address Space — a private IP address range (CIDR block) assigned to the VNet
• Subnets — segments of the VNet's address space used to organize and isolate resources
• Network Security Groups (NSGs) — filter inbound and outbound traffic at the subnet or NIC level
• Route Tables — control how traffic is routed between subnets and to external destinations

Connecting Virtual Networks

• VNet Peering — connects two VNets directly, allowing resources to communicate as if on the same network
• VPN Gateway — creates an encrypted connection between a VNet and an on-premises network over the internet
• ExpressRoute — provides a private, dedicated connection between on-premises infrastructure and Azure, bypassing the public internet

Example: Basic VNet Structure

VNet: 10.0.0.0/16
  Subnet A (Web tier): 10.0.1.0/24
  Subnet B (App tier): 10.0.2.0/24
  Subnet C (Database tier): 10.0.3.0/24

Why Virtual Networks Matter

• Provide isolation and segmentation for resources based on their role (web, app, database)
• Enable secure communication between Azure resources without exposing them to the public internet
• Form the networking foundation that other security tools, like NSGs and Azure Firewall, build on top of