Describe Network Segmentation with VNet

Network segmentation is a crucial concept in securing and managing a network. This strategy involves dividing a larger network into smaller, more manageable and secure segments, often referred to as subnets. In the realm of Microsoft Azure, these segments are typically created within a Virtual Network (VNet) to enhance both security and performance.

A Virtual Network (VNet) in Azure provides the foundation for network segmentation. It is the fundamental building block that enables Azure resources like virtual machines (VMs) and applications to securely communicate with each other, the internet, and on-premises networks. VNets provide isolation, segmentation, and control over network traffic.

Network Segmentation within a VNet is achieved by:

• Subnets: A VNet can be divided into multiple subnets, each designated for a specific purpose. For example, one subnet can be used for web servers, another for database servers, and a third for application servers. Each subnet is a separate address space within the VNet, which helps contain network traffic and can improve performance by reducing local network congestion.
• Network Security Groups (NSGs): These are used to control the inflow and outflow of network traffic to network interfaces (NIC), VMs, and subnets. NSGs can contain multiple inbound and outbound security rules that allow or deny traffic based on factors such as source and destination IP addresses, ports, and protocols.
• Network Virtual Appliances (NVAs): These are virtual machines that perform network functions like firewalls, WAN optimizers, and load balancers. NVAs can be used to control traffic between subnets, VNets, or with the internet.
• Route Tables: These are associated with subnets to control the routing of traffic between different subnets within a VNet, between VNets, and to external connections.
• Service Endpoints: By enabling service endpoints on a subnet, you can extend your VNet’s identity to an Azure service. This means that traffic from your VNet to the Azure service stays within the Azure network, which enhances security by not exposing the traffic to the public internet.
• Private Links: Private Links allow access to Azure services and your own services hosted on Azure via a private endpoint in your VNet, ensuring that traffic does not traverse the public internet and stays within the Microsoft network.
• VNet Peering: This enables connectivity between two VNets seamlessly, thus allowing resources to communicate with each other as if they are within the same network. Traffic between VNets is isolated and stays on the Microsoft backbone network.

Example Scenario:

Consider an organization deploying a multi-tier application on Azure, needing separate environments for development, testing, and production. They would start by creating a VNet. Within this VNet, they can divide the network into subnets; for instance:

• Front-end subnet for web servers
• Back-end subnet for database servers
• Application subnet for application servers
• A separate subnet for the development environment
• Another subnet for the testing environment

Each subnet would be associated with its own NSG to control the flow of traffic. The front-end subnet might only allow HTTP and HTTPS traffic from the internet, while the back-end subnet only allows SQL traffic from the application subnet. Different route tables might be used to ensure that traffic from the development environment does not mix with the production traffic.

Comparative Table of Network Segmentation Components:

Understanding and implementing network segmentation within a VNet creates a structured and secure network environment — a fundamental aspect that the SC-900 Microsoft Security, Compliance, and Identity Fundamentals exam covers. Proper segmentation ensures that an organization’s resources are isolated, protected, and can be managed effectively to minimize the risk of unauthorized access and to limit the spread of any potential security breaches within the cloud infrastructure.