Yes, it is entirely possible to configure and utilize multiple ExpressRoute circuits to enhance your connectivity to Azure services. This capability offers significant flexibility and robust design options for various enterprise networking needs.
Flexibility in ExpressRoute Circuit Configuration
You are not limited to a single ExpressRoute connection. Organizations can deploy several circuits, providing diverse pathways for their cloud connectivity. This allows for a highly adaptable network architecture:
- Same Service Provider: You can establish multiple circuits with the same network service provider. This can be useful for increasing aggregate bandwidth or creating redundant paths within a single provider's infrastructure.
- Different Service Providers: Alternatively, you have the flexibility to use different service providers for each ExpressRoute circuit. This strategy enhances resilience by diversifying your network paths, ensuring that an outage with one provider does not disrupt all cloud connectivity.
Linking Multiple Circuits to a Single Virtual Network
A key feature is the ability to connect multiple ExpressRoute circuits to the same Azure virtual network (VNet). This is particularly useful for achieving high availability and increased bandwidth for your cloud resources.
For this advanced setup to work effectively, especially for redundancy within a metropolitan area, a crucial condition applies: if the metro area has multiple ExpressRoute peering locations, your circuits must be established at different peering locations. This ensures logical separation and true diversity of paths, allowing the virtual network to intelligently route traffic across these multiple, distinct connections.
Practical Benefits and Scenarios
Deploying multiple ExpressRoute circuits offers several compelling advantages, moving beyond a single point of failure and enabling more sophisticated network designs:
- Enhanced Redundancy and High Availability: By deploying circuits with different providers or across different peering locations, you create a highly resilient architecture. If one circuit experiences an outage, traffic can automatically failover to another, ensuring continuous operation and minimal disruption to critical workloads.
- Increased Bandwidth: Multiple circuits can collectively provide higher aggregate bandwidth, allowing you to handle larger data transfers, support more concurrent connections, or accommodate the demands of bandwidth-intensive applications.
- Geographic Diversity: For global enterprises, multiple circuits can connect different on-premises locations to various Azure regions, optimizing latency for users in different geographical areas and ensuring regional resilience.
- Traffic Engineering and Segmentation: Advanced configurations can allow for specific traffic types (e.g., voice, video, mission-critical data) to utilize certain circuits, enabling more granular control over network paths and potentially improving performance for high-priority applications.
How Redundancy Works
When multiple ExpressRoute circuits are linked to the same Azure VNet, Azure's routing mechanisms, often leveraging Border Gateway Protocol (BGP), determine the optimal path. This can involve:
- Primary/Backup Paths: Designing one circuit to serve as the primary path for most traffic, with another designated as a backup path that only activates upon failure of the primary.
- Equal-Cost Multi-Path (ECMP): For scenarios where bandwidth aggregation and load balancing are desired, traffic can be distributed across multiple circuits if the routing metrics (costs) are equal, effectively increasing the total available bandwidth.
