Spoke Networks in Azure Virtual WAN
Spoke networks are essential components of the Azure Virtual WAN architecture. They represent individual virtual networks (VNets) that are connected to a Virtual WAN hub. This design allows for centralized management of connectivity, security, and routing across multiple VNets.
What is a Spoke Network?
In the context of Virtual WAN, a spoke network is typically an Azure Virtual Network (VNet) that contains your workload resources, such as virtual machines, application services, and databases. These spokes are designed to be connected to a Virtual WAN hub, which acts as a central transit point for all network traffic.
Conceptual diagram of Azure Virtual WAN architecture, illustrating spokes connecting to a central hub.
Key Characteristics of Spoke VNets:
- Workload Isolation: Each spoke VNet provides an isolated environment for specific applications or environments (e.g., development, testing, production).
- Connection to Hub: Spokes are connected to a Virtual WAN hub via VNet connections. This connection enables traffic flow between spokes and to other network destinations.
- No Direct Peering: Unlike traditional VNet peering, spokes in Virtual WAN do not have direct peering relationships with each other. All inter-spoke communication is routed through the Virtual WAN hub.
- IP Addressing: Each spoke VNet requires its own unique IP address space, which must not overlap with other connected VNets or on-premises networks.
- Shared Services: You can deploy shared services (like domain controllers, firewalls, or monitoring tools) in dedicated spoke VNets or even within the hub VNet itself, allowing multiple other spokes to consume these services.
Benefits of Using Spoke Networks:
- Scalability: Easily add or remove spoke VNets as your organization's needs evolve, without impacting existing network configurations.
- Simplified Management: Centralize network management, routing, and security policies at the Virtual WAN hub level.
- Enhanced Security: Implement consistent security policies and firewall rules across all connected spokes from a single point.
- Improved Connectivity: Efficiently connect branch offices, remote users, and other cloud providers to your Azure workloads via the hub.
Configuring a Spoke Connection:
To connect a spoke VNet to a Virtual WAN hub, you create a VNet connection within the Virtual WAN resource. This process typically involves:
- Ensuring the spoke VNet has no existing gateways or conflicting peering.
- Selecting the Virtual WAN hub to connect to.
- Assigning a unique name to the connection.
- Enabling routing options as needed (e.g., propagate to route tables).
Important Note: When a VNet is connected as a spoke to a Virtual WAN hub, it will lose any existing VNet peerings it had. Ensure you plan your network topology accordingly.
Example Scenario:
Consider an enterprise with multiple departments, each requiring its own Azure VNet for applications. These departmental VNets (e.g., Marketing VNet, Engineering VNet, Sales VNet) would be configured as spoke networks. All these spokes connect to a central Virtual WAN hub. The hub then manages routing between these spokes, connects them to the corporate on-premises network via a Site-to-Site VPN or ExpressRoute, and potentially to other Azure regions or the internet.
This approach promotes a well-organized, secure, and scalable cloud networking environment.