ExpressRoute Gateway Microsoft initiated migration
Objective The backend migration process is an automated upgrade performed by Microsoft to ensure your ExpressRoute gateways use the Standard IP SKU. This migration enhances gateway reliability and availability while maintaining service continuity. You receive notifications about scheduled maintenance windows and have options to control the migration timeline. For guidance on upgrading Basic SKU public IP addresses for other networking services, see Upgrading Basic to Standard SKU. . Important: As of September 30, 2025, Basic SKU public IPs are retired. For more information, see the official announcement. You can initiate the ExpressRoute gateway migration yourself at a time that best suits your business needs, before the Microsoft team performs the migration on your behalf. This gives you control over the migration timing. Please use the ExpressRoute Gateway Migration Tool to migrate your gateway Public IP to Standard SKU. This tool provides a guided workflow in the Azure portal and PowerShell, enabling a smooth migration with minimal service disruption. Backend migration overview The backend migration is scheduled during your preferred maintenance window. During this time, the Microsoft team performs the migration with minimal disruption. You don’t’ need to take any actions. The process includes the following steps: Deploy new gateway: Azure provisions a second virtual network gateway in the same GatewaySubnet alongside your existing gateway. Microsoft automatically assigns a new Standard SKU public IP address to this gateway. Transfer configuration: The process copies all existing configurations (connections, settings, routes) from the old gateway. Both gateways run in parallel during the transition to minimize downtime. You may experience brief connectivity interruptions may occur. Clean up resources: After migration completes successfully and passes validation, Azure removes the old gateway and its associated connections. The new gateway includes a tag CreatedBy: GatewayMigrationByService to indicate it was created through the automated backend migration Important: To ensure a smooth backend migration, avoid making non-critical changes to your gateway resources or connected circuits during the migration process. If modifications are absolutely required, you can choose (after the Migrate stage complete) to either commit or abort the migration and make your changes. Backend process details This section provides an overview of the Azure portal experience during backend migration for an existing ExpressRoute gateway. It explains what to expect at each stage and what you see in the Azure portal as the migration progresses. To reduce risk and ensure service continuity, the process performs validation checks before and after every phase. The backend migration follows four key stages: Validate: Checks that your gateway and connected resources meet all migration requirements for the Basic to Standard public IP migration. Prepare: Deploys the new gateway with Standard IP SKU alongside your existing gateway. Migrate: Cuts over traffic from the old gateway to the new gateway with a Standard public IP. Commit or abort: Finalizes the public IP SKU migration by removing the old gateway or reverts to the old gateway if needed. These stages mirror the Gateway migration tool process, ensuring consistency across both migration approaches. The Azure resource group RGA serves as a logical container that displays all associated resources as the process updates, creates, or removes them. Before the migration begins, RGA contains the following resources: This image uses an example ExpressRoute gateway named ERGW-A with two connections (Conn-A and LAconn) in the resource group RGA. Portal walkthrough Before the backend migration starts, a banner appears in the Overview blade of the ExpressRoute gateway. It notifies you that the gateway uses the deprecated Basic IP SKU and will undergo backend migration between March 7, 2026, and April 30, 2026: Validate stage Once you start the migration, the banner in your gateway’s Overview page updates to indicate that migration is currently in progress. In this initial stage, all resources are checked to ensure they are in a Passed state. If any prerequisites aren't met, validation fails and the Azure team doesn't proceed with the migration to avoid traffic disruptions. No resources are created or modified in this stage. After the validation phase completes successfully, a notification appears indicating that validation passed and the migration can proceed to the Prepare stage. Prepare stage In this stage, the backend process provisions a new virtual network gateway in the same region and SKU type as the existing gateway. Azure automatically assigns a new public IP address and re-establishes all connections. This preparation step typically takes up to 45 minutes. To indicate that the new gateway is created by migration, the backend mechanism appends _migrate to the original gateway name. During this phase, the existing gateway is locked to prevent configuration changes, but you retain the option to abort the migration, which deletes the newly created gateway and its connections. After the Prepare stage starts, a notification appears showing that new resources are being deployed to the resource group: Deployment status In the resource group RGA, under Settings → Deployments, you can view the status of all newly deployed resources as part of the backend migration process. In the resource group RGA under the Activity Log blade, you can see events related to the Prepare stage. These events are initiated by GatewayRP, which indicates they are part of the backend process: Deployment verification After the Prepare stage completes, you can verify the deployment details in the resource group RGA under Settings > Deployments. This section lists all components created as part of the backend migration workflow. The new gateway ERGW-A_migrate is deployed successfully along with its corresponding connections: Conn-A_migrate and LAconn_migrate. Gateway tag The newly created gateway ERGW-A_migrate includes the tag CreatedBy: GatewayMigrationByService, which indicates it was provisioned by the backend migration process. Migrate stage After the Prepare stage finishes, the backend process starts the Migrate stage. During this stage, the process switches traffic from the existing gateway ERGW-A to the new gateway ERGW-A_migrate. Gateway ERGW-A_migrate: Old gateway (ERGW-A) handles traffic: After the backend team initiates the traffic migration, the process switches traffic from the old gateway to the new gateway. This step can take up to 15 minutes and might cause brief connectivity interruptions. New gateway (ERGW-A_migrate) handles traffic: Commit stage After migration, the Azure team monitors connectivity for 15 days to ensure everything is functioning as expected. The banner automatically updates to indicate completion of migration: During this validation period, you can’t modify resources associated with both the old and new gateways. To resume normal CRUD operations without waiting15 days, you have two options: Commit: Finalize the migration and unlock resources. Abort: Revert to the old gateway, which deletes the new gateway and its connections. To initiate Commit before the 15-day window ends, type yes and select Commit in the portal. When the commit is initiated from the backend, you will see “Committing migration. The operation may take some time to complete.” The old gateway and its connections are deleted. The event shows as initiated by GatewayRP in the activity logs. After old connections are deleted, the old gateway gets deleted. Finally, the resource group RGA contains only resources only related to the migrated gateway ERGW-A_migrate: The ExpressRoute Gateway migration from Basic to Standard Public IP SKU is now complete. Frequently asked questions How long will Microsoft team wait before committing to the new gateway? The Microsoft team waits around 15 days after migration to allow you time to validate connectivity and ensure all requirements are met. You can commit at any time during this 15-day period. What is the traffic impact during migration? Is there packet loss or routing disruption? Traffic is rerouted seamlessly during migration. Under normal conditions, no packet loss or routing disruption is expected. Brief connectivity interruptions (typically less than 1 minute) might occur during the traffic cutover phase. Can we make any changes to ExpressRoute Gateway deployment during the migration? Avoid making non-critical changes to the deployment (gateway resources, connected circuits, etc.). If modifications are absolutely required, you have the option (after the Migrate stage) to either commit or abort the migration.Azure Networking 2025: Powering cloud innovation and AI at global scale
In 2025, Azure’s networking platform proved itself as the invisible engine driving the cloud’s most transformative innovations. Consider the construction of Microsoft’s new Fairwater AI datacenter in Wisconsin – a 315-acre campus housing hundreds of thousands of GPUs. To operate as one giant AI supercomputer, Fairwater required a single flat, ultra-fast network interconnecting every GPU. Azure’s networking team delivered: the facility’s network fabric links GPUs at 800 Gbps speeds in a non-blocking architecture, enabling 10× the performance of the world’s fastest supercomputer. This feat showcases how fundamental networking is to cloud innovation. Whether it’s uniting massive AI clusters or connecting millions of everyday users, Azure’s globally distributed network is the foundation upon which new breakthroughs are built. In 2025, the surge of AI workloads, data-driven applications, and hybrid cloud adoption put unprecedented demands on this foundation. We responded with bold network investments and innovations. Each new networking feature delivered in 2025, from smarter routing to faster gateways, was not just a technical upgrade but an innovation enabling customers to achieve more. Recapping the year’s major releases across Azure Networking services and key highlights how AI both drive and benefit from these advancements. Unprecedented connectivity for a hybrid and AI era Hybrid connectivity at scale: Azure’s network enhancements in 2025 focused on making global and hybrid connectivity faster, simpler, and ready for the next wave of AI-driven traffic. For enterprises extending on-premises infrastructure to Azure, Azure ExpressRoute private connectivity saw a major leap in capacity: Microsoft announced support for 400 Gbps ExpressRoute Direct ports (available in 2026) to meet the needs of AI supercomputing and massive data volumes. These high-speed ports – which can be aggregated into multi-terabit links – ensure that even the largest enterprises or HPC clusters can transfer data to Azure with dedicated, low-latency links. In parallel, Azure VPN Gateway performance reached new highs, with a generally available upgrade that delivers up to 20 Gbps aggregate throughput per gateway and 5 Gbps per individual tunnel. This is a 3× increase over previous limits, enabling branch offices and remote sites to connect to Azure even more seamlessly without bandwidth bottlenecks. Together, the ExpressRoute and VPN improvements give customers a spectrum of high-performance options for hybrid networking – from offices and datacenters to the cloud – supporting scenarios like large-scale data migrations, resilient multi-site architectures, and hybrid AI processing. Simplified global networking: Azure Virtual WAN (vWAN) continued to mature as the one-stop solution for managing global connectivity. Virtual WAN introduced forced tunneling for Secure Virtual Hubs (now in preview), which allows organizations to route all Internet-bound traffic from branch offices or virtual networks back to a central hub for inspection. This capability simplifies the implementation of a “backhaul to hub” security model – for example, forcing branches to use a central firewall or security appliance – without complex user-defined routing. Empowering multicloud and NVA integration: Azure recognizes that enterprise networks are diverse. Azure Route Server improvements enhanced interoperability with customer equipment and third-party network virtual appliances (NVAs). Notably, Azure Route Server now supports up to 500 virtual network connections (spokes) per route server, a significant scale boost that enables larger hub-and-spoke topologies and simplified Border Gateway Protocol (BGP) route exchange even in very large environments. This helps customers using SD-WAN appliances or custom firewalls in Azure to seamlessly learn routes from hundreds of VNet spokes – maintaining central routing control without manual configuration. Additionally, Azure Route Server introduced a preview of hub routing preference, giving admins the ability to influence BGP route selection (for example, preferring ExpressRoute over a VPN path, or vice versa). This fine-grained control means hybrid networks can be tuned for optimal performance and cost. Resilience and reliability by design Azure’s growth has been underpinned by making the network “resilient by default.” We shipped tools to help validate and improve network resiliency. ExpressRoute Resiliency Insights was released for general availability – delivering an intelligent assessment of an enterprise’s ExpressRoute setup. This feature evaluates how well your ExpressRoute circuits and gateways are architected for high availability (for example, using dual circuits in diverse locations, zone-redundant gateways, etc.) and assigns a resiliency index score as a percentage. It will highlight suboptimal configurations – such as routes advertised on only one circuit, or a gateway that isn’t zone-redundant – and provide recommendations for improvement. Moreover, Resiliency Insights includes a failover simulation tool that can test circuit redundancy by mimicking failures, so you can verify that your connections will survive real-world incidents. By proactively monitoring and testing resilience, Azure is helping customers achieve “always-on” connectivity even in the face of fiber cuts, hardware faults, or other disruptions. Security, governance, and trust in the network As enterprises entrust more core business to Azure, the platform’s networking services advanced on security and governance – helping customers achieve Zero Trust networks and high compliance with minimal complexity. Azure DNS now offers DNS Security Policies with Threat Intelligence feeds (GA). This capability allows organizations to protect their DNS queries from known malicious domains by leveraging continuously updated threat intel. For example, if a known phishing domain or C2 (command-and-control) hostname appears in DNS queries from your environment, Azure DNS can automatically block or redirect those requests. Because DNS is often the first line of detection for malware and phishing activities, this built-in filtering provides a powerful layer of defense that’s fully managed by Azure. It’s essentially a cloud-delivered DNS firewall using Microsoft’s vast threat intelligence – enabling all Azure customers to benefit from enterprise-grade security without deploying additional appliances. Network traffic governance was another focus. The introduction of forced tunneling in Azure Virtual WAN hubs (preview) shared above is a prime example where networking meets security compliance. Optimizing cloud-native and edge networks We previewed DNS intelligent traffic control features – such as filtering DNS queries to prevent data exfiltration and applying flexible recursion policies – which complement the DNS Security offering in safeguarding name resolution. Meanwhile, for load balancing across regions, Azure Traffic Manager’s behind-the-scenes upgrades (as noted earlier) improved reliability, and it’s evolving to integrate with modern container-based apps and edge scenarios. AI-powered networking: Both enabling and enabled by AI We are infusing AI into networking to make management and troubleshooting more intelligent. Networking functionality in Azure Copilot accelerates tasks like never before: it outlines the best practices instantly and troubleshooting that once required combing through docs and logs can be conversational. It effectively democratizes networking expertise, helping even smaller IT teams manage sophisticated networks by leveraging AI recommendations. The future of cloud networking in an AI world As we close out 2025, one message is clear: networking is strategic. The network is no longer a static utility – it is the adaptive circulatory system of the cloud, determining how far and fast customers can go. By delivering higher speeds, greater reliability, tighter security, and easier management, Azure Networking has empowered businesses to connect everything to anything, anywhere – securely and at scale. These advances unlock new scenarios: global supply chains running in real-time over a trusted network, multi-player AR/VR and gaming experiences delivered without lag, and AI models trained across continents. Looking ahead, AI-powered networking will become the norm. The convergence of AI and network tech means we will see more self-optimizing networks that can heal, defend, and tune themselves with minimal human intervention.Inter-Hub Connectivity Using Azure Route Server
By Mays_Algebary shruthi_nair As your Azure footprint grows with a hub-and-spoke topology, managing User-Defined Routes (UDRs) for inter-hub connectivity can quickly become complex and error-prone. In this article, we’ll explore how Azure Route Server (ARS) can help streamline inter-hub routing by dynamically learning and advertising routes between hubs, reducing manual overhead and improving scalability. Baseline Architecture The baseline architecture includes two Hub VNets, each peered with their respective local spoke VNets as well as with the other Hub VNet for inter-hub connectivity. Both hubs are connected to local and remote ExpressRoute circuits in a bowtie configuration to ensure high availability and redundancy, with Weight used to prefer the local ExpressRoute circuit over the remote one. To maintain predictable routing behavior, the VNet-to-VNet configuration on the ExpressRoute Gateway should be disabled. Note: Adding ARS to an existing Hub with Virtual Network Gateway will cause downtime that expect to last 10 minutes. Scenario 1: ARS and NVA Coexist in the Hub Option A: Full Traffic Inspection ARS and NVA Coexist in the Hub In this scenario, ARS is deployed in each Hub VNet, alongside the Network Virtual Appliances (NVAs). NVA1 in Region1 establishes BGP peering with both the local ARS (ARS1) and the remote ARS (ARS2). Similarly, NVA2 in Region2 peers with both ARS2 (local) and ARS1 (remote). Let’s break down what each BGP peering relationship accomplishes. For clarity, we’ll focus on Region1, though the same logic applies to Region2: NVA1 Peering with Local ARS1 Through BGP peering with ARS1, NVA1 dynamically learns the prefixes of Spoke1 and Spoke2 at the OS level, eliminating the need to manually configure these routes. The same applies for NVA2 learning Spoke3 and Spoke4 prefixes via its BGP peering with ARS2. NVA1 Peering with Remote ARS2 When NVA1 peers with ARS2, the Spoke1 and Spoke2 prefixes are propagated to ARS2. ARS2 then injects these prefixes into NVA2 at both the NIC level with NVA1 as the next hop, and at the OS level. This mechanism removes the need for UDRs on the NVA subnets to enable inter-hub routing. Additionally, ARS2 advertises the Spoke1 and Spoke2 prefixes to both ExpressRoute circuits (EXR2 and EXR1 due to bowtie configuration) via GW2, making them reachable from on-premises through either EXR1 or EXR2. 👉Important: To ensure that ARS2 accepts and propagates Spoke1/Spoke2 prefixes received via NVA1, AS-Override must be enabled. Without AS-Override, BGP loop prevention will block these routes at ARS2, since both ARS1 and ARS2 use the default ASN 65515, and ARS2 will consider the route as already originated locally. The same principle applies in reverse for Spoke3 and Spoke4 prefixes being advertised from NVA2 to ARS1. Traffic Flow Inter-Hub Traffic: Spoke VNets are configured with UDRs that contain only a default route (0.0.0.0/0) pointing to the local NVA as the next hop. Additionally, the “Propagate Gateway Routes” setting should be set to False to ensure all traffic, whether East-West (intra-hub/inter-hub) or North-South (to/from internet), is forced through the local NVA for inspection. Local NVAs will have the next hop to the other region spokes injected at the NIC level by local ARS, pointing to the other region NVA, for example NVA2 will have next hop to Spoke1 and Spoke2 as NVA1 (10.0.1.4) and vice versa. Why are UDRs still needed on spokes if ARS handles dynamic routing? Even with ARS in place, UDRs are required to maintain control of the next hop for traffic inspection. For instance, if Spoke1 and Spoke2 do not have UDRs, they will learn the remote spoke prefixes (e.g., Spoke3/Spoke4) injected via ARS1, which received them from NVA2. This results in Spoke1/Spoke2 attempting to route traffic directly to NVA2, a path that is invalid, since the spokes don’t have the path to NVA2. The UDR ensures traffic correctly routes through NVA1 instead. On-Premises Traffic: To explain the on-premises traffic flow, we'll break it down into two directions: Azure to on-premises, and on-premises to Azure. Azure to On-Premises Traffic Flow: As previously noted, Spokes send all traffic, including traffic to on-premises, via NVA1 due to the default route in the UDR. NVA1 then routes traffic to the local ExpressRoute circuit, using Weight to prefer the local path over the remote. Note: While NVA1 learns on-premises prefixes from both local and remote ARSs at the OS level, this doesn’t affect routing decisions. The actual NIC-level route injection determines the next hop, ensuring traffic is sent via the correct path—even if the OS selects a different “best” route internally. The screenshot below from NVA1 shows four next hops to the on-premises network 10.2.0.0/16. These include the local ARS (ARS1: 10.0.2.5 and 10.0.2.4) and the remote ARS (ARS2: 10.1.2.5 and 10.1.2.4). On-Premises to Azure Traffic Flow In a bowtie ExpressRoute configuration, Azure VNet prefixes are advertised to on-premises through both local and remote ExpressRoute circuits. Because of this dual advertisement, the on-premises network must ensure optimal path selection when routing traffic to Azure. From Azure side, to maintain traffic symmetry, add UDRs at the GatewaySubnet (GW1 and GW2) with specific routes to the local Spoke VNets, using the local NVA as the next hop. This ensures return traffic flows back through the same path it entered. 👉How Does the ExpressRoute Edge Router Select the Optimal Path? You might ask: If Spoke prefixes are advertised by both GW1 and GW2, how does the ExpressRoute edge router choose the best path? (e.g., diagram below shows EXR1 learns Region1 prefixes from GW1 and GW2) Here’s how: Edge routers (like EXR1) receive the same Spoke prefixes from both gateways. However, these routes have different AS-Path lengths: - Routes from the local gateway (GW1) have a shorter AS-Path. - Routes from the remote gateway (GW2) have a longer AS-Path because NVA1’s ASN (e.g., 65001) is prepended twice as part of the AS-Override mechanism. As a result, the edge router (EXR1) will prefer the local path from GW1, ensuring efficient and predictable routing. For example: EXR1 receives Spoke1, Spoke2, and Hub1-VNet prefixes from both GW1 and GW2. But because the path via GW1 has a shorter AS-Path, EXR1 will select that as the best route. (Refer to the diagram below for a visual of the AS-Path difference). Final Traffic Flow: Option-A Insights: This design simplifies UDR configuration for inter-hub routing, especially useful when dealing with non-contiguous prefixes or operating across multiple hubs. For simplicity, we used a single NVA in each Hub-VNet while explaining the setup and traffic flow throughout this article. However, a high available (HA) NVA deployment is recommended. To maintain traffic symmetry in an HA setup, you’ll need to enable the next-hop IP feature when peering with Azure Route Server (ARS). When on-premises traffic inspection is required, the UDR setup in the GatewaySubnet becomes more complex as the number of Spokes increases. Additionally, each route table is currently limited to 600 UDR entries. As your Azure network scales, keep in mind that Azure Route Server supports a maximum of 8 BGP peers per instance (as of the time writing this article). This limit can impact architectures involving multiple NVAs or hubs. Option B: Bypass On-Premises Inspection If on-premises traffic inspection is not required, NVAs can advertise a supernet prefix summarizing the local Spoke VNets to the remote ARS. This approach provides granular control over which traffic is routed through the NVA and eliminates the need for BGP peering between the local NVA and local ARS. All other aspects of the architecture remain the same as described in Option A. For example, NVA2 can advertise the supernet 192.168.2.0/23 (supernet of Spoke3 and Spoke4) to ARS1. As a result, Spoke1 and Spoke2 will learn this route with NVA2 as the next hop. To ensure proper routing (as discussed earlier) and inter-hub inspection, you need apply a UDR in Spoke1 and Spoke2 that overrides this exact supernet prefix, redirecting traffic to NVA1 as the next hop. At the same time, traffic destined for on-premises will follow the system route through the local ExpressRoute gateway, bypassing NVA1 altogether. In this setup: UDRs on the Spokes should have "Propagate Gateway Routes" set to True. No UDRs are needed in the GatewaySubnet. 👉Can NVA2 Still Advertise Specific Spoke Prefixes? You might wonder: Can NVA2 still advertise specific prefixes (e.g., Spoke3 and Spoke4) learned from ARS2 to ARS1 instead of a supernet? Yes, this is technically possible, but it requires maintaining BGP peering between NVA2 and ARS2. However, this introduces UDR complexity in Spoke1 and Spoke2, as you'd need to manually override each specific prefix. This also defeats the purpose of using ARS for simplified route propagation, undermining the efficiency and scalability of the design. Bypass On-Premises Inspection Final Traffic Flow: Option B: Bypass on-premises inspection traffic flow Option-B Insights: This approach reduces the number of BGP peerings per ARS. Instead of maintaining two BGP sessions (local NVA and remote NVA) per Hub, you can limit it to just one, preserving capacity within ARS’s 8-peer limit for additional inter-hub NVA peerings. Each NVA should advertise a supernet prefix to the remote ARS. This can be challenging if your Spokes don’t use contiguous IP address spaces, as described in Option B. Scenario 2: ARS in the Hub and the NVA in Transit VNet In Scenario 1, we highlighted that when on-premises inspection is required, managing UDRs at the GatewaySubnet becomes increasingly complex as the number of Spoke VNets grows. This is due to the need for UDRs to include specific prefixes for each Spoke VNet. In this scenario, we eliminate the need to apply UDRs at the GatewaySubnet altogether. In this design, the NVA will be deployed in Transit VNet, where: Transit-VNet will be peered with local Spoke VNets and with the local Hub-VNet to enable intra-Hub and on-premises connectivity. Transit-VNet also peered with remote Transit VNets (e.g., Transit-VNet1 peered with Transit-VNet2) to handle inter-Hub connectivity through the NVAs. Additionally, Transit-VNets are peered with remote Hub-VNets, to establish BGP peering with the remote ARS. NVAs OS will need to add static routes for the local Spoke VNets prefixes, it can be specific or it can supernet prefix, which will later be advertised to ARSs over BGP Peering, then ARS will advertise it to on-premises via ExpressRoute. NVAs will BGP peer with local ARS and also with the remote ARS. To understand the reasoning behind this design, let’s take a closer look at the setup in Region1, focusing on how ARS and NVA are configured to connect to Region2. This will help illustrate both inter-hub and on-premises connectivity. The same concept applies in reverse from Region2 to Region1. Inetr-Hub: To enable NVA1 in Region1 to learn prefixes from Region2, NVA2 will configure static routes at the OS level for Spoke3 and Spoke4 (or their supernet prefix) and advertise them to ARS1 via remote BGP peering. As a result, these prefixes will be received by NVA1, both at the NIC level, with NVA2 as the next hop, and at the OS level for proper routing. Spoke1 and Spoke2 will have a UDR with a default route pointing to NVA1 as the next hop. For instance, when Spoke1 needs to communicate with Spoke3, the traffic will first route through NVA1. NVA1 will then forward the traffic to NVA2 using VNet peering between the two Hubs. A similar configuration will be applied in Region2, where NVA1 will configure static routes at the OS level for Spoke1 and Spoke2 (or their supernet prefix) and advertise them to ARS2 via remote BGP peering, as a result, these prefixes will be received by NVA2, both at the NIC level (injected by ARS2), with NVA1 as the next hop, and at the OS level for proper routing. Note: At the OS level, NVA1 learns Spoke3 and Spoke4 prefixes from both local and remote ARSs. However, the NIC-level route injection determines the actual next hop, so even if the OS selects a different best route, it won’t affect forwarding behavior. same applies to NVA2. On-Premises Traffic: To explain the on-premises traffic flow, we'll break it down into two directions: Azure to on-premises, and on-premises to Azure. Azure to On-Premises Traffic Flow: Spokes in Region1 route all traffic through NVA1 via a default route defined in their UDRs. Because of BGP peering between NVA1 and ARS1, ARS1 advertises the Spoke1 and Spoke2 (or their supernet prefix) to on-premises through ExpressRoute (EXR1). The Transit-VNet1 (hosting NVA1) is peered with Hub1-VNet, with “Use Remote Gateway” enabled. This allows NVA1 to learn on-premises prefixes from the local ExpressRoute gateway (GW1), and traffic to on-premises is routed through the local ExpressRoute circuit (EXR1) due to higher BGP Weight configuration. Note: At the OS level, NVA1 learns on-prem prefixes from both local and remote ARSs. However, the NIC-level route injection determines the actual next hop, so even if the OS selects a different best route, it won’t affect forwarding behavior. same applies to NVA2. On-Premises to Azure Traffic Flow: Through BGP peering with ARS1, NVA1 enables ARS1 to advertise Spoke1 and Spoke2 (or their supernet prefix) to both EXR1 and EXR2 circuits (due to the ExpressRoute bowtie setup). Additionally, due to BGP peering between NVA1 and ARS2, ARS2 also advertises Spoke1 and Spoke2 (or their supernet prefix) to EXR2 and EXR1 circuits. As a result, both ExpressRoute edge routers in Region1 and Region2 learn the same Spoke prefixes (or their supernet prefix) from both GW1 and GW2, with identical AS-Path lengths, as shown below. EXR1 learns Region1 Spokes's supernet prefixes from GW1 and GW2 This causes non-optimal inbound routing, where traffic from on-premises destined to Region1 Spokes may first land in Region2’s Hub2-VNet before traversing to NVA1 in Region1. However, return traffic from Spoke1 and Spoke2 will always exit through Hub1-VNet. To prevent suboptimal routing, configure NVA1 to prepend the AS path for Spoke1 and Spoke2 (or their supernet prefix) when advertising them to the remote ARS2. Likewise, ensure NVA2 prepends the AS path for Spoke3 and Spoke4 (or their supernet prefix) when advertising to ARS1. This approach helps maintain optimal routing under normal conditions and during ExpressRoute failover scenarios. Below diagram shows NVA1 is setting AS-Prepend for Spoke1 and Spoke2 supernet prefix when BGP peer with remote ARS (ARS1), same will apply for NVA2 when advertising Spoke3 and Spoke4 prefixes to ARS1. Final Traffic Flow: Full Inspection: Traffic flow when NVA in Transit-VNet Insights: This solution is ideal when full traffic inspection is required. Unlike Scenario 1 - Option A, it eliminates the need for UDRs in the GatewaySubnet. When ARS is deployed in a VNet (typically in Hub VNets), the VNet will be limited to 500 VNet peerings (as of the time writing this article). However, in this design, Spokes peer with the Transit-VNet instead of directly with the ARS VNet, allowing you to scale beyond the 500-peer limit by leveraging Azure Virtual Network Manager (AVNM) or submitting a support request. Some enterprise customers may encounter the 1,000-route advertisement limit on the ExpressRoute circuit from the ExpressRoute gateway. In traditional hub-and-Spoke designs, there's no native control over what is advertised to ExpressRoute. With this architecture, NVAs provide greater control over route advertisement to the circuit. For simplicity, we used a single NVA in each Hub-VNet while explaining the setup and traffic flow throughout this article. However, a high available (HA) NVA deployment is recommended. To maintain traffic symmetry in an HA setup, you’ll need to enable the next-hop IP feature when peering with Azure Route Server (ARS). This design does require additional VNet peerings, including: Between Transit-VNets (inter-region), Between Transit-VNets and local Spokes, and Between Transit-VNets and both local and remote Hub-VNets.
Can only remote into azure vm from DC
Hi all, I have set up a site to site connection from on prem to azure and I can remote in via the main dc on prem but not any other server or ping from any other server to the azure. Why can I only remote into the azure VM from the server that has Routing and remote access? Any ideas on how I can fix this?
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Hi We have an IPVPN ExpressRoute connection back to our MPLS. We also have a central Internet breakout from our MPLS, its quite small, only 300mb. we don't want to increase the bandwidth on that circuit and at the moment it is getting a little over used by workers connecting to on-premise and Azure service via the client VPN they have. We want to look at the possibility of bringing up a P2S VPN in Azure that can also utilise the ExpressRoute for connectivity back down to the MPLS. We also have multiple VNGs setup that are linked to other Azure subs and a spare VNG that has a larger GatewaySubnet than the others (/27) Has anyone successfully brought up another VNG in the same GatewaySubnet asn an ExpressRoute VNG to allow P2S connections back either into the Azure environment or using the ExpressRoute back into an on-premise LAN (via the MPLS)? if you have, get in touch because I'd like to know how you managed it. I have looked at Virtual WAN, but that would entail bringing down the current ER which is a no no at the moment. thanks
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Is there any way we can have express route peer BGP directly with on Prem Firewall via /29 subnet The firewall has active / standby and VIP. The express route peering require two /30 . if I have an active standby and VIP on the firewall how is that going to work ?Azure Networking Portfolio Consolidation
Overview Over the past decade, Azure Networking has expanded rapidly, bringing incredible tools and capabilities to help customers build, connect, and secure their cloud infrastructure. But we've also heard strong feedback: with over 40 different products, it hasn't always been easy to navigate and find the right solution. The complexity often led to confusion, slower onboarding, and missed capabilities. That's why we're excited to introduce a more focused, streamlined, and intuitive experience across Azure.com, the Azure portal, and our documentation pivoting around four core networking scenarios: Network foundations: Network foundations provide the core connectivity for your resources, using Virtual Network, Private Link, and DNS to build the foundation for your Azure network. Try it with this link: Network foundations Hybrid connectivity: Hybrid connectivity securely connects on-premises, private, and public cloud environments, enabling seamless integration, global availability, and end-to-end visibility, presenting major opportunities as organizations advance their cloud transformation. Try it with this link: Hybrid connectivity Load balancing and content delivery: Load balancing and content delivery helps you choose the right option to ensure your applications are fast, reliable, and tailored to your business needs. Try it with this link: Load balancing and content delivery Network security: Securing your environment is just as essential as building and connecting it. The Network Security hub brings together Azure Firewall, DDoS Protection, and Web Application Firewall (WAF) to provide a centralized, unified approach to cloud protection. With unified controls, it helps you manage security more efficiently and strengthen your security posture. Try it with this link: Network security This new structure makes it easier to discover the right networking services and get started with just a few clicks so you can focus more on building, and less on searching. What you’ll notice: Clearer starting points: Azure Networking is now organized around four core scenarios and twelve essential services, reflecting the most common customer needs. Additional services are presented within the context of these scenarios, helping you stay focused and find the right solution without feeling overwhelmed. Simplified choices: We’ve merged overlapping or closely related services to reduce redundancy. That means fewer, more meaningful options that are easier to evaluate and act on. Sunsetting outdated services: To reduce clutter and improve clarity, we’re sunsetting underused offerings such as white-label CDN services and China CDN. These capabilities have been rolled into newer, more robust services, so you can focus on what’s current and supported. What this means for you Faster decision-making: With clearer guidance and fewer overlapping products, it's easier to discover what you need and move forward confidently. More productive sales conversations: With this simplified approach, you’ll get more focused recommendations and less confusion among sellers. Better product experience: This update makes the Azure Networking portfolio more cohesive and consistent, helping you get started quickly, stay aligned with best practices, and unlock more value from day one. The portfolio consolidation initiative is a strategic effort to simplify and enhance the Azure Networking portfolio, ensuring better alignment with customer needs and industry best practices. By focusing on top-line services, combining related products, and retiring outdated offerings, Azure Networking aims to provide a more cohesive and efficient product experience. Azure.com Before: Our original Solution page on Azure.com was disorganized and static, displaying a small portion of services in no discernable order. After: The revised solution page is now dynamic, allowing customers to click deeper into each networking and network security category, displaying the top line services, simplifying the customer experience. Azure Portal Before: With over 40 networking services available, we know it can feel overwhelming to figure out what’s right for you and where to get started. After: To make it easier, we've introduced four streamlined networking hubs each built around a specific scenario to help you quickly identify the services that match your needs. Each offers an overview to set the stage, key services to help you get started, guidance to support decision-making, and a streamlined left-hand navigation for easy access to all services and features. Documentation For documentation, we looked at our current assets as well as created new assets that aligned with the changes in the portal experience. Like Azure.com, we found the old experiences were disorganized and not well aligned. We updated our assets to focus on our top-line networking services, and to call out the pillars. Our belief is these changes will allow our customers to more easily find the relevant and important information they need for their Azure infrastructure. Azure Network Hub Before the updates, we had a hub page organized around different categories and not well laid out. In the updated hub page, we provided relevant links for top-line services within all of the Azure networking scenarios, as well as a section linking to each scenario's hub page. Scenario Hub pages We added scenario hub pages for each of the scenarios. This provides our customers with a central hub for information about the top-line services for each scenario and how to get started. Also, we included common scenarios and use cases for each scenario, along with references for deeper learning across the Azure Architecture Center, Well Architected Framework, and Cloud Adoption Framework libraries. Scenario Overview articles We created new overview articles for each scenario. These articles were designed to provide customers with an introduction to the services included in each scenario, guidance on choosing the right solutions, and an introduction to the new portal experience. Here's the Load balancing and content delivery overview: Documentation links Azure Networking hub page: Azure networking documentation | Microsoft Learn Scenario Hub pages: Azure load balancing and content delivery | Microsoft Learn Azure network foundation documentation | Microsoft Learn Azure hybrid connectivity documentation | Microsoft Learn Azure network security documentation | Microsoft Learn Scenario Overview pages What is load balancing and content delivery? | Microsoft Learn Azure Network Foundation Services Overview | Microsoft Learn What is hybrid connectivity? | Microsoft Learn What is Azure network security? | Microsoft Lea Improving user experience is a journey and in coming months we plan to do more on this. Watch out for more blogs over the next few months for further improvements.Connectivity options between Hub-and-Spoke and Azure Virtual WAN
Contents Overview Scenario 1 – Traffic hair-pinning using ExpressRoute Scenario 2 – Build a virtual tunnel (SD-WAN or IPSec) Scenario 3 – vNet Peering and vHub connection coexistence Scenario 4 – Transit virtual network for decentralized vNets Conclusion Bonus Overview This article is going to discuss different options that interconnect the Hub and Spoke networking with Virtual WAN for migrations scenarios. The goal of this article is to expand on additional options that can help customers to migrate to their existing Hub and Spoke topology to Azure Virtual WAN. You can find a comprehensive article Migrate to Azure Virtual WAN to go over several considerations during the migration process. The focus of this article is to focus only on the connectivity to facilitate the migration process. Therefore, it is important to note that the interconnectivity options listed here are intended to be used in the short term to ensure a temporary coexistence between both topologies while the workload on the Spoke vNets with the end goal of disconnecting both environments after migration is completed. This article mainly discusses scenarios with a Virtual WAN Secured Virtual Hub; exceptions are noted where applicable. The setup assumes the use of routing intent and route policies, replacing the previous approach of using route tables to secure Virtual Hubs. For more information, please consult: How to configure Virtual WAN Hub routing intent and routing policies. Scenario 1 – Traffic hair-pinning using ExpressRoute circuits To begin the migration, ensure that the target Virtual WAN Hub (vHub) includes all necessary components. For existing vHubs equipped with Firewalls, SD-WAN, VPN (Point-to-Site or Site-to-Site), confirm that these elements are also present and correctly configured on the target Virtual WAN. Additionally, for any migrated Spoke, an optional vNet peering can be maintained to the original Hub vNet if there are dependencies, such as shared services (DNS, Active Directory, and other services). Make sure that the peering configuration has the option for using remote gateway disabled, because once connected to the vHub, the vNet connection requires using remote gateway to be enabled. On this scenario traffic between Hub and Spoke and Virtual WAN Hub is facilitated using an ExpressRoute circuit that is connected to both environments. When a single circuit is connected to both environments’ routes will be exchanged between both environments, and it will hairpin at the MSEE (Microsoft Enterprise Edge) routers. This scenario is a similar approach used described in the article: Migrate to Azure Virtual WAN. Connectivity flow: Source Destination Data Path Spoke vNet Migrated Spokes vNets 1. vNet Hub Firewall 2. vNet ExpressRoute Gateway 3. MSEE via Hairpin 4. vHub ExpressRoute Gateway 5. vHub Firewall Spoke vNet Branches (VPN/SD-WAN) 1. vNet Hub Firewall 2. vNet SD-WAN NVA or VPN Gateway Spoke vNet On-premises DC 1. vNet Hub Firewall 2. ExpressRoute Gateway 3. ExpressRoute Circuit (MSEE) 4. Provider/Customer Migrated vNet Branches (VPN/SD-WAN) 1. vHub Firewall 2. vHub SD-WAN NVA or VPN Gateway Migrated vNet On-premises DC 1. vNet Hub Firewall 2. vNet ExpressRoute Gateway 3. ExpressRoute Circuit (MSEE) 4. Provider/Customer Note: Connectivity also considers that return traffic follows the same path and components. Pros Traffic stays in the Microsoft Backbone and does not go over the Provider or Customer CPE. Built-in route provided by the Azure Platform (this is configurable, see considerations). Cons Expect high latency. Traffic between VNET Hub and vHubs crosses MSEE routers outside the Azure Region in a Cloud Exchange facility, increasing latency due to the distance to the region. Single point of failure. Because the MSEE is located at the Edge location, an outage at that site can impact communication. To ensure redundancy, you can utilize a second MSEE at a different Edge location within the same metro area to achieve redundancy and lower latency. Additionally, a second MSEE in different metro areas can also provide redundancy, although this might result in increased latency. Considerations A new feature has been introduced to block MSEE hairpin. To enable this scenario, you need to activate Allow Traffic from remote Virtual WAN Networks (on VNET Hub side) and Allow Traffic from non-Virtual WAN Networks (on Virtual WAN Hub side). For more details, refer to this article: Customisation controls for connectivity between Virtual Networks over ExpressRoute.. Scenario 2 – Build a virtual tunnel (SD-WAN or IPSec) The same prerequisites for the target vHub apply for this option before beginning the migration. However, instead of utilizing ExpressRoute transit, in this scenario you establish a direct virtual tunnel between the existing VNET Hub and the vHub to facilitate communication. There are several options for achieving this, including: Use Azure native VPN Gateway on both VNET Hub and vHub for IPSec tunnels. Up to four tunnels can be created when VNET Hub VPN Gateway is configured to Active/Active (by default, vHub VPN Gateways are already Active/Active). It is important to consider that customers can use either BGP or static routing when implementing this option. However, BGP will be restricted, if the VNET VPN Gateway is the only gateway present, you can use custom ASN other than 65515. If there is another gateway, such as ExpressRoute or Azure Route Server, ASN must be set to 65515. Since vHub VPN Gateway does not allow custom ASN at this moment (65515 is the default ASN), static routes will be required for this setup. Use 3 rd party NVA to establish SD-WAN connectivity between both sides or IPSec tunnel. Using this option, you can leverage either static or BGP routing, where BGP will offer better integration with vHub and less administrative effort. Connectivity flow: Source Destination Data Path Spoke vNet Migrated Spokes vNets 1. vNet Hub Firewall 2. vNet Hub SD-WAN NVA or VPN Gateway 3. vHub Hub SD-WAN NVA or VPN Gateway 4. vHub Firewall Spoke vNet Branches (VPN/SD-WAN) 1. vNet Hub Firewall 2. vNet Hub SD-WAN NVA or VPN Gateway Spoke vNet On-premises DC 1. vNet Hub Firewall 2. ExpressRoute Gateway 3. MSEE Hairpin 4. Provider/Customer Migrated vNet Branches (VPN/SD-WAN) 1. vHub Firewall 2. SD-WAN NVA or VPN Gateway Migrated vNet On-premises DC 1. vNet Hub Firewall 2. ExpressRoute Gateway 3. MSEE Hairpin 4. Provider/Customer Note: Connectivity also considers that return traffic follows the same path and components. Pros Traffic remains within the Microsoft Backbone in the region, resulting in lower latency compared to Option 1. Cons Administrative overhead when using static routes and managing extra network components. Cost of adding a new VPN Gateway or 3 rd party NVA to build the virtual tunnel Throughput may be limited based on the type of virtual tunnel technology used. This limitation can be mitigated by adding multiple tunnels, which require BGP + ECMP to balance traffic between them. It is important to note that Azure allows up to eight tunnels, which is the maximum number of programmed routes for the same networks with different next hops, indicating the specific tunnel. Scenario 3 – vNet Peering and vHub connection coexistence In this scenario, spokes vNet originally connected to vNet Hub are migrated to the vHub while maintaining existing peering with the vNet Hub but with the Use Remote Gateway configuration disabled. This allows the migrated vNets to retain connectivity with the source vNet Hub while also connecting to the vHub. The connection to the vHub necessitates the Use Remote Gateway, which directs all traffic towards on-premises to use the vHub. To connect with other spokes via vHub, the migrated vNet needs a UDR with routes to the vNet spoke prefixes using the vNet Hub Firewall as the next hop. Use route summarization for contiguous prefixes or enter specific prefixes if they are not. Additionally, enable Gateway Propagation in the UDR so migrated Spoke vNets can learn routes from the vHub (RFC 1918, default route, or both). Connectivity flow: Source Destination Data Path Spoke vNet Migrated Spokes vNet 1. vNet Hub Firewall Spoke vNet Branches (VPN/SD-WAN) 1. vNet Hub Firewall 2. vNet SD-WAN NVA or VPN Gateway Spoke vNet On-premises DC 1. vNet Hub Firewall 2. ExpressRoute Gateway 3. ExpressRoute Circuit (MSEE) 4. Provider/Customer Migrated vNet Branches (VPN/SD-WAN) 1. vHub Firewall 2. vHub SD-WAN NVA or VPN Gateway Migrated vNet On-premises DC 1. vHub Firewall 2. vHub ExpressRoute Gateway 3. ExpressRoute Circuit (MSEE) 4. Provider/Customer Note: Connectivity means that return traffic follows the same path and components. Pros Traffic remains within the Microsoft Backbone in the region, resulting in lower latency compared to option 1. No throughput limitation imposed by virtual tunnels compared to option 2. Throughput will be limited by the VM size. Cons Administrative overhead to adjust the UDR to reach the Spoke vNets on connected over the vNet Hub. Scenario 4 – Transit virtual network for decentralized vNets This use case involves a decentralized virtual network model where each customer has an ExpressRoute Gateway for connectivity to on-premises systems. Traffic between virtual networks is managed using virtual network peering, based on the specific connectivity requirements of the customer. Each virtual network has its own gateway, which prevents connecting them directly to the virtual hub because the remote gateway option needs to be enabled. If the customer can tolerate the downtime associated with removing the Express Route Gateway from the migrated vNet, they have the option to establish a direct vNet connection to the vHub, thereby simplifying the solution. This process typically takes approximately 45 minutes, excluding the rollback procedure which would require an additional 45 minutes, potentially making this approach prohibitive for most customers. However, customers with existing Azure workloads often aim to minimize downtime. As illustrated in the diagram below, they can create a transit vNet equipped with a firewall or a Network Virtual Appliance (NVA) with routing capabilities. This configuration allows the migrated vNet to establish regular peering, thereby maintaining connectivity without significant disruption. The solution illustrated on this section uses a static route propagation at the vNet connection level towards the Transit vNet, which now requires non Secured-Virtual WAN hubs (note that support for static route propagation is on the Virtual WAN roadmap). Alternatively, you can use BGP peering from the Firewall or NVA to program the migrated vNets summary prefixes. For Firewall implementations with BGP it is recommended to leverage Next hop IP support for Virtual WAN where traffic flows over a load balance feature to ensure traffic symmetry. In that scenario you can also leverage Secured-vHubs. The migration process also necessitates adjustments to the routes for the migrated vNET to facilitate traffic flow to on-premises systems using the vHUB. This includes utilizing static routes at the connection from the Transit vNet to the vHub to advertise a summary route via the Firewall in the transit vNET to ensure return traffic and proper advertisement to the on-premises environment. Once the route configurations are established, the ExpressRoute connection can be removed. The customer can then proceed to Step 2, which will allow them to make the final adjustments and complete the full integration with the vHub following the outlined steps. Remove ExpressRoute Gateway. Create the vNet connection to the vHub, that will allow the specific Migrated vNet prefix to advertise to the vHub as well as leak down to the ExpressRoute. Once the step 2 is completed the traffic should start to flow over the vNET connection to the Vub. Removed the vNet peering to the Transit vNET. Connectivity flow: Source Destination Data Path vNet1/VNet2 Migrated Spokes vNet 1. Direct vNet peering vNet1/VNet2 Branches (VPN/SD-WAN) 1. ExpressRoute Gateway 2. ExpressRoute Circuit (MSEE) 3. Provider/Customer 4. VPN/SD-WAN vNet1/VNet2 On-premises DC 1. ExpressRoute Gateway 2. ExpressRoute Circuit (MSEE) 3. Provider/Customer Migrated vNet (Step1) Branches (VPN/SD-WAN) 1. Transit Firewall 2. vHub SD-WAN NVA or VPN Gateway Migrated vNet (Step1) On-premises DC 1. Transit Firewall 2. vHub ExpressRoute Gateway 3. ExpressRoute Circuit (MSEE) 4. Provider/Customer Migrated vNet (Step2) Branches (VPN/SD-WAN) 1. vHub SD-WAN NVA or VPN Gateway Migrated vNet (Step2) On-premises DC 1. vHub ExpressRoute Gateway 2. ExpressRoute Circuit (MSEE) 3. Provider/Customer Note: Connectivity means that return traffic follows the same path and components. Pros Traffic remains on the Microsoft backbone, ensuring minimal latency. Not the same throughput limits associated with option 2 solution (virtual tunnels). Cons Administrative overhead associated with maintaining the additional transit virtual network, including user-defined route management and vHub vNet Connection static route configuration. Costs incurred from operating any supplementary firewalls (FWs) or network virtual appliances (NVAs) in the transit vNet. Conclusion This article outlined four strategies for migrating from Hub and Spoke networking to Azure Virtual WAN—ExpressRoute hair pinning, VPN or SD-WAN virtual tunnels, vNet peering with vHub connections, and transit virtual networks for decentralized vNets—highlighting their pros, cons, and administrative considerations. It is important to assess which approach best fits your needs by weighing each scenario's advantages and drawbacks. Bonus The diagrams in Excalidraw format related to this blog post are available in the following GitHub repository.Network Redundancy Between AVS, On-Premises, and Virtual Networks in a Multi-Region Design
By Mays_Algebary shruthi_nair Establishing redundant network connectivity is vital to ensuring the availability, reliability, and performance of workloads operating in hybrid and cloud environments. Proper planning and implementation of network redundancy are key to achieving high availability and sustaining operational continuity. This article focuses on network redundancy in multi-region architecture. For details on single-region design, refer to this blog. The diagram below illustrates a common network design pattern for multi-region deployments, using either a Hub-and-Spoke or Azure Virtual WAN (vWAN) topology, and serves as the baseline for establishing redundant connectivity throughout this article. In each region, the Hub or Virtual Hub (VHub) extends Azure connectivity to Azure VMware Solution (AVS) via an ExpressRoute circuit. The regional Hub/VHub is connected to on-premises environments by cross-connecting (bowtie) both local and remote ExpressRoute circuits, ensuring redundancy. The concept of weight, used to influence traffic routing preferences, will be discussed in the next section. The diagram below illustrates the traffic flow when both circuits are up and running. Design Considerations If a region loses its local ExpressRoute connection, AVS in that region will lose connectivity to the on-premises environment. However, VNets will still retain connectivity to on-premises via the remote region’s ExpressRoute circuit. The solutions discussed in this article aim to ensure redundancy for both AVS and VNets. Looking at the diagram above, you might wonder: why do we need to set weights at all, and why do the AVS-ER connections (1b/2b) use the same weight as the primary on-premises connections (1a/2a)? Weight is used to influence routing decisions and ensure optimal traffic flow. In this scenario, both ExpressRoute circuits, ER1-EastUS and ER2-WestUS, advertise the same prefixes to the Azure ExpressRoute gateway. As a result, traffic from the VNet to on-premises would be ECMPed across both circuits. To avoid suboptimal routing and ensure that traffic from the VNets prefers the local ExpressRoute circuit, a higher weight is assigned to the local path. It’s also critical that the ExpressRoute gateway connection to on-premises (1a/2a) and to AVS (1b/2b), is assigned the same weight. Otherwise, traffic from the VNet to AVS will follow a less efficient route as AVS routes are also learned over ER1-EastUS via Global Reach. For instance, VNets in EastUS will connect to AVS EUS through ER1-EastUS circuit via Global Reach (as shown by the blue dotted line), instead of using the direct local path (orange line). This suboptimal routing is illustrated in the below diagram. Now let us see what solutions we can have to achieve redundant connectivity. The following solutions will apply to both Hub-and-Spoke and vWAN topology unless noted otherwise. Note: The diagrams in the upcoming solutions will focus only on illustrating the failover traffic flow. Solution1: Network Redundancy via ExpressRoute in Different Peering Location In the solution, deploy an additional ExpressRoute circuit in a different peering location within the same metro area (e.g., ER2–PeeringLocation2), and enable Global Reach between this new circuit and the existing AVS ExpressRoute (e.g., AVS-ER1). If you intend to use this second circuit as a failover path, apply prepends to the on-premises prefixes advertised over it. Alternatively, if you want to use it as an active-active redundant path, do not prepend routes, in this case, both AVS and Azure VNets will ECMP to distribute traffic across both circuits (e.g., ER1–EastUS and ER–PeeringLocation2) when both are available. Note: Compared to the Standard Topology, this design removes both the ExpressRoute cross-connect (bowtie) and weight settings. When adding a second circuit in the same metro, there's no benefit in keeping them, otherwise traffic from the Azure VNet will prefer the local AVS circuit (AVS-ER1/AVS-ER2) to reach on-premises due to the higher weight, as on-premises routes are also learned over AVS circuit (AVS-ER1/AVS-ER2) via Global Reach. Also, when connecting the new circuit (e.g., ER–Peering Location2), remove all weight settings across the connections. Traffic will follow the optimal path based on BGP prepending on the new circuit, or load-balance (ECMP) if no prepend is applied. Note: Use public ASN to prepend the on-premises prefix as AVS circuit (e.g., AVS-ER) will strip the private ASN toward AVS. Solution Insights Ideal for mission-critical applications, providing predictable throughput and bandwidth for backup. It could be cost prohibitive depending on the bandwidth of the second circuit. Solution2: Network Redundancy via ExpressRoute Direct In this solution, ExpressRoute Direct is used to provision multiple circuits from a single port pair in each region, for example, ER2-WestUS and ER4-WestUS are created from the same port pair. This allows you to dedicate one circuit for local traffic and another for failover to a remote region. To ensure optimal routing, prepend the on-premises prefixes using public ASN on the newly created circuit (e.g., ER3-EastUS and ER4-WestUS). Remove all weight settings across the connections; traffic will follow the optimal path based on BGP prepending on the new circuit. For instance, if ER1-EastUS becomes unavailable, traffic from AVS and VNets in the EastUS region will automatically route through ER4-WestUS circuit, ensuring continuity. Note: Compared to the Standard Topology, this design connects the newly created ExpressRoute circuits (e.g., ER3-EastUS/ER4-WestUS) to the remote region of ExpressRoute gateway (black dotted lines) instead of having the bowtie to the primary circuits (e.g., ER1-EastUS/ER2-WestUS). Solution Insights Easy to implement if you have ExpressRoute Direct. ExpressRoute Direct supports over- provisioning where you can create logical ExpressRoute circuits on top of your existing ExpressRoute Direct resource of 10-Gbps or 100-Gbps up to the subscribed Bandwidth of 20 Gbps or 200 Gbps. For example, you can create two 10-Gbps ExpressRoute circuits within a single 10-Gbps ExpressRoute Direct resource (port pair). Ideal for mission-critical applications, providing predictable throughput and bandwidth for backup. Solution3: Network Redundancy via ExpressRoute Metro Metro ExpressRoute is a new configuration that enables dual-homed connectivity to two different peering locations within the same city. This setup enhances resiliency by allowing traffic to continue flowing even if one peering location goes down, using the same circuit. Solution Insights Higher Resiliency: Provides increased reliability with a single circuit. Limited regional availability: Currently available in select regions, with more being added over time. Cost-effective: Offers redundancy without significantly increasing costs. Solution4: Deploy VPN as a Backup to ExpressRoute This solution mirrors solution 1 for a single region but extends it to multiple regions. In this approach, a VPN serves as the backup path for each region in the event of an ExpressRoute failure. In a Hub-and-Spoke topology, a backup path to and from AVS can be established by deploying Azure Route Server (ARS) in the hub VNet. ARS enables seamless transit routing between ExpressRoute and the VPN gateway. In vWAN topology, ARS is not required; the vHub's built-in routing service automatically provides transitive routing between the VPN gateway and ExpressRoute. In this design, you should not cross-connect ExpressRoute circuits (e.g., ER1-EastUS and ER2-WestUS) to the ExpressRoute gateways in the Hub VNets (e.g., Hub-EUS or Hub-WUS). Doing so will lead to routing issues, where the Hub VNet only programs the on-premises routes learned via ExpressRoute. For instance, in the EastUS region, if the primary circuit (ER1-EastUS) goes down, Hub-EUS will receive on-premises routes from both the VPN tunnel and the remote ER2-WestUS circuit. However, it will prefer and program only the ExpressRoute-learned routes from ER2-WestUS circuit. Since ExpressRoute gateways do not support route transitivity between circuits, AVS connected via AVS-ER will not receive the on-premises prefixes, resulting in routing failures. Note: In vWAN topology, to ensure optimal route convergence when failing back to ExpressRoute, you should prepend the prefixes advertised from on-premises over the VPN. Without route prepending, VNets may continue to use the VPN as the primary path to on-premises. If prepend is not an option, you can trigger the failover manually by bouncing the VPN tunnel. Solution Insights Cost-effective and straightforward to deploy. Increased Latency: The VPN tunnel over the internet adds latency due to encryption overhead. Bandwidth Considerations: Multiple VPN tunnels might be needed to achieve bandwidth comparable to a high-capacity ExpressRoute circuit (e.g., over 1G). For details on VPN gateway SKU and tunnel throughput, refer to this link. As you can't cross connect ExpressRoute circuits, VNets will utilize the VPN for failover instead of leveraging remote region ExpressRoute circuit. Solution5: Network Redundancy-Multiple On-Premises (split-prefix) In many scenarios, customers advertise the same prefix from multiple on-premises locations to Azure. However, if the customer can split prefixes across different on-premises sites, it simplifies the implementation of failover strategy using existing ExpressRoute circuits. In this design, each on-premises advertises region-specific prefixes (e.g., 10.10.0.0/16 for EastUS and 10.70.0.0/16 for WestUS), along with a common supernet (e.g., 10.0.0.0/8). Under normal conditions, AVS and VNets in each region use longest prefix match to route traffic efficiently to the appropriate on-premises location. For instance, if ER1-EastUS becomes unavailable, AVS and VNets in EastUS will automatically fail over to ER2-WestUS, routing traffic via the supernet prefix to maintain connectivity. Solution Insights Cost-effective: no additional deployment, using existing ExpressRoute circuits. Advertising specific prefixes over each region might need additional planning. Ideal for mission-critical applications, providing predictable throughput and bandwidth for backup. Solution6: Prioritize Network Redundancy for One Region Over Another If you're operating under budget constraints and can prioritize one region (such as hosting critical workloads in a single location) and want to continue using your existing ExpressRoute setup, this solution could be an ideal fit. In this design, assume AVS in EastUS (AVS-EUS) hosts the critical workloads. To ensure high availability, AVS-ER1 is configured with Global Reach connections to both the local ExpressRoute circuit (ER1-EastUS) and the remote circuit (ER2-WestUS). Make sure to prepend the on-premises prefixes advertised to ER2-WestUS using public ASN to ensure optimal routing (no ECMP) from AVS-EUS over both circuits (ER1-EastUS and ER2-WestUS). On the other hand, AVS in WestUS (AVS-WUS) is connected via Global Reach only to its local region ExpressRoute circuit (ER2-WestUS). If that circuit becomes unavailable, you can establish an on-demand Global Reach connection to ER1-EastUS, either manually or through automation (e.g., a triggered script). This approach introduces temporary downtime until the Global Reach link is established. You might be thinking, why not set up Global Reach between the AVS-WUS circuit and remote region circuits (like connecting AVS-ER2 to ER1-EastUS), just like we did for AVS-EUS? Because it would lead to suboptimal routing. Due to AS path prepending on ER2-WestUS, if both ER1-EastUS and ER2-WestUS are linked to AVS-ER2, traffic would favor the remote ER1-EastUS circuit since it presents a shorter AS path. As a result, traffic would bypass the local ER2-WestUS circuit, causing inefficient routing. That is why for AVS-WUS, it's better to use on-demand Global Reach to ER1-EastUS as a backup path, enabled manually or via automation, only when ER2-WestUS becomes unavailable. Note: VNets will failover via local AVS circuit. E.g., HUB-EUS will route to on-prem through AVS-ER1 and ER2-WestUS via Global Reach Secondary (purple line). Solution Insights Cost-effective Workloads hosted in AVS within the non-critical region will experience downtime if the local region ExpressRoute circuit becomes unavailable, until the on-demand Global Reach connection is established. Conclusion Each solution has its own advantages and considerations, such as cost-effectiveness, ease of implementation, and increased resiliency. By carefully planning and implementing these solutions, organizations can ensure operational continuity and optimal traffic routing in multi-region deployments.
