Hub-Spoke Topology in Azure Virtual WAN

The hub-spoke topology is a networking pattern that can be implemented in Azure Virtual WAN. It is designed to provide a centralized, scalable, and secure network architecture for your cloud resources. This topology uses a central Virtual Hub (the "hub") to connect various spokes (Virtual Networks) and on-premises sites.

Conceptual Diagram

Diagram illustrating the Hub-Spoke architecture with Virtual WAN.

Key Components

• Virtual Hub: The central point of connectivity. It contains routing, VPN gateways, and ExpressRoute gateways.
• Spoke Virtual Networks: Individual Virtual Networks (VNets) that are connected to the Virtual Hub. Each spoke can host specific application workloads.
• Connections: These are the links between the spokes and the Virtual Hub, and between the Virtual Hub and on-premises sites.
• Route Tables: Used to control traffic flow between different parts of the network.
• Gateways: VPN and ExpressRoute gateways within the Virtual Hub enable connectivity to on-premises networks and other clouds.

Benefits of Hub-Spoke with Virtual WAN

• Centralized Management: Simplifies network management by centralizing connectivity and security policies in the Virtual Hub.
• Scalability: Easily add or remove spoke VNets and on-premises connections as your organization grows.
• Security: Provides a secure perimeter with centralized firewall and security controls.
• Cost-Effectiveness: Reduces complexity and potentially costs by sharing common network services.
• Optimal Routing: Enables efficient routing between spokes and to/from on-premises locations.

Implementing Hub-Spoke

Setting up a hub-spoke topology with Azure Virtual WAN involves several steps:

1. Create a Virtual WAN resource: This is the top-level resource that manages your Virtual WAN deployment.
2. Create a Virtual Hub: Deploy a Virtual Hub within your Virtual WAN. This hub will serve as the central transit point.
3. Deploy Hub Network Services: Configure routing, VPN gateways, or ExpressRoute gateways within the Virtual Hub as needed.
4. Connect Spoke VNets: Establish VNet connections from your spoke VNets to the Virtual Hub. This allows spokes to communicate with each other and with the hub.
5. Connect On-Premises Sites: Configure Site-to-Site VPN or ExpressRoute circuits to connect your on-premises networks to the Virtual Hub.
6. Configure Routing: Define route tables and associations to control how traffic flows between different network segments.

# Using Azure CLI (conceptual example)
az network vwan vnet-connection create \
  --name MyVNetConnection \
  --resource-group MyResourceGroup \
  --vwan-hub MyVirtualHub \
  --vnet SpokeVNet1 \
  --hub-routing-gravity Global \
  --enable-internet-security false
                

Considerations

• IP Address Allocation: Plan your IP address spaces carefully to avoid overlaps between VNets and on-premises networks.
• Routing Prefixes: Understand how routes are propagated and learned in the Virtual Hub.
• Security Policies: Implement Network Security Groups (NSGs) and Azure Firewall for granular control over traffic.
• Service Endpoints and Private Endpoints: Ensure these are configured correctly for secure access to Azure services.

The hub-spoke topology, powered by Azure Virtual WAN, offers a robust and flexible solution for modern cloud networking. By centralizing connectivity, it simplifies management, enhances security, and ensures efficient communication across your Azure environment and hybrid cloud infrastructure.