Azure Virtual Network (VNet) Design Best Practices

Designing a robust and scalable Azure Virtual Network (VNet) is crucial for the success of your cloud deployments. This document outlines best practices to ensure your VNet architecture is secure, efficient, and manageable.

1. IP Addressing and Subnetting

• Plan your IP address space carefully: Choose a private IP address space that is large enough to accommodate future growth. Avoid overlapping with on-premises IP address spaces if hybrid connectivity is planned. Use RFC 1918 private address ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16).
• Use appropriate CIDR blocks for subnets: Allocate subnet sizes based on the expected number of resources. Start with smaller subnets and expand if necessary, rather than over-allocating large blocks initially. Consider the default route table and service endpoints.
• Limit the number of subnets: While granular control is good, an excessive number of subnets can increase management complexity. Group resources logically within subnets.
• Reserve IP addresses: The first four and the last IP address in each subnet are reserved by Azure and cannot be assigned to resources. Ensure your subnet sizing accounts for this.

2. Network Security

• Implement Network Security Groups (NSGs): Use NSGs to filter network traffic to and from Azure resources in an Azure virtual network, with security rules that allow or deny network traffic. Apply NSGs at the subnet or NIC level, or both.
• Leverage Azure Firewall: For centralized network traffic inspection and policy enforcement, deploy Azure Firewall. It provides threat intelligence-based filtering, application-level filtering, and network filtering.
• Utilize Azure Private Link: For secure access to Azure PaaS services without exposing them to the public internet, use Azure Private Link. This provides a private endpoint within your VNet.
• Segment workloads with VNets/Subnets: Create separate VNets or subnets for different tiers of your application (e.g., web tier, application tier, data tier) and use NSGs or firewalls to control traffic flow between them.
• Regularly review NSG rules: Audit your NSG rules periodically to ensure they are still relevant and secure. Remove unnecessary rules and tighten access controls.

3. Connectivity and Peering

• Use VNet peering for inter-VNet communication: VNet peering is the recommended method for connecting VNets within the same region or across different regions. It allows resources in different VNets to communicate with each other as if they were in the same network.
• Consider Global VNet Peering for cross-region connectivity: If your application spans multiple regions, Global VNet Peering enables communication between VNets in different Azure regions.
• Plan for on-premises connectivity: Use Azure VPN Gateway or Azure ExpressRoute for connecting your on-premises network to your Azure VNet. Design your connectivity architecture based on bandwidth, latency, and reliability requirements.
• Avoid transit routing: In a hub-spoke topology, ensure spokes do not transit traffic through other spokes. Route traffic to on-premises or to the internet through the hub VNet.

4. Management and Scalability

• Adopt a Hub-Spoke topology: This architecture provides a centralized hub VNet for security, management, and connectivity services (like NAT Gateway, Azure Firewall, VPN Gateway), with spoke VNets hosting your workloads. This simplifies management and enhances security.
• Use Tags for organization: Tag your VNets, subnets, and associated resources to improve manageability, cost tracking, and automation.
• Monitor network performance: Utilize Azure Network Watcher and Azure Monitor to gain insights into network traffic, diagnose connectivity issues, and monitor performance metrics.
• Plan for future scaling: Design your VNet with expansion in mind. Consider future IP address needs, potential peering requirements, and the addition of new services.

5. Naming Conventions

Establish clear and consistent naming conventions for VNets, subnets, NSGs, and other network resources. This improves readability and reduces confusion.

Conclusion

A well-designed VNet is the foundation of a secure and scalable Azure environment. By following these best practices, you can create a network infrastructure that meets your current needs and can adapt to future demands.

Further Reading:

• Azure VNet Documentation
• Network Security Group Overview
• Azure Firewall Best Practices