Azure Virtual WAN Route Table Concepts
Azure Virtual WAN is a networking service that brings together Azure networking capabilities, security, and routing functionalities into a single operational interface. Route tables are fundamental to how traffic is directed within your Virtual WAN environment. Understanding their concepts is crucial for effective network design and troubleshooting.
Conceptual Diagram: Traffic Flow in Virtual WAN
Note: This is a conceptual illustration. Actual network topology may vary.
Core Components of Virtual WAN Routing
Virtual WAN employs a hub-and-spoke architecture. Each Virtual WAN Hub acts as a central point for routing traffic between different network components. Route tables are associated with these hubs and dictate how packets are forwarded.
1. Hub Route Table
Every Virtual WAN Hub has a primary route table. This table contains routes that define how traffic is directed from the hub to various connected spokes (like Virtual Networks, Site-to-Site VPNs, ExpressRoute circuits, and P2S VPNs).
- Default Routes: The hub route table automatically learns routes from connected spokes.
- Propagated Routes: Routes can be learned from connections and propagated to the hub's route table.
- Static Routes: You can manually add static routes to the hub's route table for specific destinations not learned automatically.
2. Connection Route Tables
Each connection (e.g., a VNet connection to the hub, a VPN site connection) can have its own associated route table. This allows for granular control over traffic originating from or destined for that specific connection.
- Learning Routes: Connections learn routes from the hub's route table by default.
- Route Propagation: You can configure which routes are propagated from a connection to the hub.
- Association: A connection is associated with a specific route table in the hub.
Key Routing Concepts
Route Propagation
This is the process by which routes are advertised from one network entity to another within Virtual WAN. For example, routes from a VNet connected to a hub are propagated to the hub's route table. Similarly, routes from a VPN site can be propagated to the hub.
Route Association
This refers to which route table is actively used by a connection to make forwarding decisions. A VNet connection, for instance, is associated with a particular route table in the hub. When traffic arrives at the hub from this VNet, the associated route table determines where to send it next.
Static Routes
These are manually configured routes that you add to a route table. They are useful for directing traffic to specific destinations or overriding learned routes. You can define a destination prefix and the next hop for these routes.
Effective Routes
This is the combination of all routes present in a route table, including learned, propagated, and static routes. Understanding effective routes is crucial for diagnosing connectivity issues.
Benefits of Virtual WAN Routing
- Centralized Management: Manage routing for your entire network from a single pane of glass.
- Simplified Connectivity: Easily connect VNets, on-premises sites, and remote users.
- Scalability: Designed to scale with your organization's growth.
- Advanced Security: Integrate with Azure Firewall and Network Security Groups for comprehensive security.
- Route Filtering: Control which routes are propagated and learned for better security and isolation.
Common Scenarios
Understanding route tables helps in scenarios like:
- Ensuring seamless communication between different VNets connected to the same hub.
- Enabling secure access from on-premises networks to Azure resources via VPN or ExpressRoute.
- Directing traffic from remote users to specific Azure services.
- Implementing network segmentation using different route tables for different traffic flows.
For detailed configuration and management, refer to the official Azure documentation on Azure Virtual WAN Route Tables.