Azure Virtual Networks (VNets) and Subnets

Table of Contents

Introduction

Azure Virtual Networks (VNets) are foundational building blocks in Azure networking, allowing communication between Azure resources securely.
A VNet is like a private network in the cloud, similar to a local area network (LAN) in an on-premises environment.
Subnets help divide a VNet into smaller, isolated networks for better security and performance.
VNets and Subnets are crucial for managing network traffic, enabling secure communication, and organizing cloud resources efficiently.

A Virtual Network (VNet) is a logically isolated network within Azure that allows resources to communicate securely with each other, the internet, and on-premises networks.
It acts like a private cloud network where Azure services, such as virtual machines (VMs), databases, and web apps, can communicate securely.

Isolation and Security
- VNets are completely isolated from other VNets unless explicitly connected.
- Supports Network Security Groups (NSGs) to control inbound and outbound traffic.
Custom IP Addressing
- Uses IPv4 and IPv6 address ranges, allowing users to define custom IP spaces.
- Supports public and private IPs for secure communication.
Subnets for Network Segmentation
- A VNet can be divided into multiple subnets for organizing resources.
- Subnets improve security, traffic management, and performance.
Connectivity Options
- VNets can be connected to other VNets, on-premises networks, and the internet using:
  - VNet Peering – Connects multiple VNets seamlessly.
  - VPN Gateway – Securely connects an on-premises network to an Azure VNet.
  - ExpressRoute – Provides a dedicated private connection between on-premises and Azure.
Integration with Azure Services
- VNets allow integration with Azure Virtual Machines (VMs), Azure Kubernetes Service (AKS), Azure SQL Database, and other Azure services.
- Supports Azure Load Balancer and Application Gateway for traffic distribution.

A Subnet is a smaller, segmented part of a VNet that helps divide the network into logical sections.
Subnets help organize and isolate resources, improving network security and performance.

Logical Network Segmentation
- Divides a VNet into multiple smaller networks for better management.
- Example: A web subnet for web servers and a database subnet for databases.
Traffic Isolation and Security
- Each subnet has its own security rules and policies to control traffic.
- Uses Network Security Groups (NSGs) and Route Tables to manage access control.
Custom Address Ranges
- Each subnet gets a portion of the VNet’s IP address space.
- Ensures efficient IP address allocation and resource management.
Public vs. Private Subnets
- Public Subnets – Have access to the internet and require a public IP.
- Private Subnets – Only accessible within the VNet, no direct internet access.
Supports Different Azure Services
- Subnets can host Azure Virtual Machines (VMs), App Services, Databases, Kubernetes clusters, and more.
- Example: A front-end subnet for web apps and a back-end subnet for databases.

Feature	Virtual Network (VNet)	Subnet
Definition	A private, isolated network in Azure	A smaller segment within a VNet
Purpose	Provides a secure network for Azure resources	Divides a VNet into logical sections
Security	Uses Network Security Groups (NSGs) and Firewalls	Uses NSGs and access control per subnet
IP Addressing	Defines an address range for all subnets	Uses a portion of the VNet’s IP address space
Communication	Connects with Azure services, VNets, and on-premises networks	Manages internal resource communication

✔ Hosting Web Applications

Use Case: A company wants to host a web app securely.
Solution:
- A VNet is created with two subnets:
  - A web subnet for hosting front-end web servers.
  - A database subnet for storing user data securely.

✔ Hybrid Cloud Networking

Use Case: A business wants to connect on-premises servers with Azure resources.
Solution:
- A VNet is configured with VPN Gateway to connect with the on-premises network.
- Subnets are used for different departments (HR, IT, Finance).

✔ Secure Data Storage

Use Case: A company wants to store customer data securely.
Solution:
- A VNet is created with a private subnet for database storage.
- NSGs restrict external access to prevent unauthorized access.

C – To create a secure, isolated network for Azure resources
- Why others are incorrect?
  - A – VNets are private, not public networks.
  - B – VNets connect within Azure, not between cloud providers.
  - D – VNets manage various services, not just VMs.
  - E – VNets handle networking, not storage.
A – Subnets allow dividing a VNet into smaller logical sections
- Why others are incorrect?
  - B, C, D, E – Subnets are not mandatory for connecting VNets, they support NSGs, and they do not require public IPs.
C – By configuring VPN Gateway or ExpressRoute
- Why others are incorrect?
  - A, B, D, E – Secure communication between on-premises and Azure requires VPN Gateway or ExpressRoute.
C – It allows better traffic isolation, security, and resource organization
- Why others are incorrect?
  - A, B, D, E – Subnets improve security and performance rather than causing security issues or increasing latency.
B – Virtual Network Peering
- Why others are incorrect?
  - A, C, D, E – These services do not enable direct VNet communication.

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