Leveraging Azure’s Default Routing and System Routes for Secure and Efficient Network Design

AMJ Cloud Technologies worked with a global logistics company specializing in real-time shipment tracking and route optimization to transition their infrastructure to Microsoft Azure. This case study highlights how we leveraged Azure’s default routing and system routes to create a secure, efficient, and scalable network foundation.

Situation

The client was migrating from a traditional data center to a cloud-native infrastructure on Azure, deploying multiple Virtual Networks (VNets) for frontend services, backend processing, and regional microservices. They required a secure and reliable network setup without overcomplicating routing during the early migration phase.

Challenge

The client faced challenges adapting to Azure’s software-defined networking model:

• Understanding Azure’s default traffic routing across subnets and external destinations.
• Ensuring secure internal service-to-service communication without misconfigurations.
• Preventing unintended exposure of private resources to the public internet.
• Maintaining performance and security for Azure platform service access.
• Supporting future VNet peering and hybrid connectivity scenarios.

Solution: Harnessing Azure’s Default Routing Logic

We conducted a comprehensive audit of the client’s VNet architecture and leveraged Azure’s default system route table to simplify routing. The solution was implemented over five weeks by a team of cloud architects and network engineers.

Action

Key steps included:

• Internal VNet Routing:

  • Utilized system routes with a Next Hop Type of “Virtual Network” for seamless intra-VNet traffic (e.g., between AppTierSubnet and DataTierSubnet) via Azure’s internal fabric.

• Default Internet Route Awareness:

  • Monitored the default 0.0.0.0/0 route (Next Hop Type: “Internet”) to prevent unintended egress, advising the client to configure NSGs for outbound traffic control.

• Private IP Space Isolation:

  • Leveraged Azure’s automatic drop rules for RFC 1918 ranges (Next Hop Type: “None”) to ensure internal IP traffic remained within the VNet.

• Carrier-Grade NAT and Management IP Protection:

  • Ensured routes for RFC 6598 (100.64.0.0/10) and Azure management IPs were set to “None,” preventing interference with Azure’s internal systems.

• Service Endpoint Routing Optimization:

  • Enabled Service Endpoints for Azure SQL and Blob Storage, adding system routes to route traffic via Azure’s private backbone.

• Future-Proofing for Peering and Hybrid Connectivity:

  • Planned for dynamic system route updates for VNet Peering (Next Hop Type: “Virtual Network”) and VPN Gateway/ExpressRoute (Next Hop Type: “Virtual Network Gateway”).

• Testing and Validation:

  • Validated secure communication, performance, and compliance through traffic monitoring and testing.

Results

The solution delivered significant outcomes:

• Simplified Network Management: Achieved secure routing without custom UDRs, accelerating deployment.
• Minimized Risk of Data Leakage: Automatic drop rules for private and management IP ranges prevented misconfigured egress.
• Improved Confidence in Cloud Networking: Clarified Azure’s routing behavior, enabling the network team to troubleshoot and plan expansions effectively.
• Seamless Platform Integration: Service Endpoints optimized performance and security for Azure service access.

Technologies Used

• Azure Virtual Network (VNet): Foundation for network segmentation.
• Azure System Route Table (Default): Managed default routing behavior.
• Virtual Network Subnet Gateways: Enabled intra-VNet communication.
• Azure Service Endpoints: Optimized access to Azure services.
• RFC 1918 and RFC 6598 Routing Protection: Ensured private IP isolation.
• Azure VNet Peering (Planned): Prepared for future network expansion.
• Azure VPN Gateway / ExpressRoute (Planned): Supported hybrid connectivity.

Key Use Cases

This approach is ideal for:

• Organizations transitioning to Azure with limited cloud networking experience.
• Businesses seeking secure and simple routing without custom appliances.
• Teams planning for future peering or hybrid connectivity.

Key Takeaways

By leveraging Azure’s default routing and system routes, we enabled the client to establish a secure and performant network foundation without overengineering. Understanding Azure’s built-in routing behavior ensured operational simplicity and enterprise-grade networking. AMJ Cloud Technologies is committed to delivering practical cloud solutions for seamless migrations.

Architectural Diagram