Understanding Azure Custom Routing Architecture – Part 4

Overview: This architecture demonstrates a custom routing setup within an Azure Virtual Network (VNet). It uses a Network Virtual Appliance (NVA) to route traffic between subnets. This configuration is commonly used for scenarios requiring custom traffic inspection, advanced routing capabilities, or security enforcement beyond the default Azure capabilities.

Components:

  1. Virtual Network (VNet):
    • The overarching network structure in Azure which contains multiple subnets.
    • Provides isolation and segmentation of different network segments.
  2. Subnets:
    • Subnet 1
    • Subnet 2
    • Subnet 3
    • Each subnet is a segmented part of the VNet. They can contain different resources such as virtual machines, application services, etc.
  3. Network Virtual Appliance (NVA):
    • A virtual appliance responsible for managing and directing network traffic.
    • Typically used for advanced routing, traffic inspection, or firewall purposes.
    • Ensures that all traffic between the subnets passes through it for inspection and routing decisions.

Architecture Details:

  • Inter-Subnet Traffic:
    • All traffic between Subnet 1, Subnet 2, and Subnet 3 is routed through the NVA.
    • This routing is enforced using user-defined routes (UDRs) associated with each subnet, directing traffic to the NVA IP address.
  • Custom Route Tables:
    • Each subnet is associated with a custom route table.
    • These route tables contain routes directing traffic to the NVA, ensuring that the NVA handles traffic between subnets.

Routing Flow:

  1. Traffic originating from any subnet (Subnet 1, Subnet 2, Subnet 3) is directed to the NVA.
  2. The NVA processes the traffic according to its configuration (e.g., firewall rules, inspection policies).
  3. After processing, the NVA routes the traffic to the appropriate destination subnet.
  4. This ensures a controlled and inspected flow of traffic across the network.

Use Cases:

  • Security Inspection: Implementing deep packet inspection and enforcing security policies.
  • Advanced Routing: Custom routing decisions based on specific business or application requirements.
  • Traffic Management: Load balancing, traffic shaping, or QoS policies can be applied.

Advantages:

  • Enhanced Security: All inter-subnet traffic is inspected and controlled.
  • Flexibility: Custom routing rules and security policies can be dynamically applied.
  • Scalability: The architecture can be scaled by adding more NVAs or subnets as needed.

This architecture leverages Azure’s flexible networking capabilities to implement a highly customizable routing and security solution, suitable for complex network environments requiring stringent control and inspection of inter-subnet traffic.