Delivering web applications over IPv6
The IPv4 address space pool has been exhausted for some time now, meaning there is no new public address space available for allocation from Internet Registries. The internet continues to run on IPv4 through technical measures such as Network Address Translation (NAT) and Carrier Grade NAT, and reallocation of address space through IPv4 address space trading. IPv6 will ultimately be the dominant network protocol on the internet, as IPv4 life-support mechanisms used by network operators, hosting providers and ISPs will eventually reach the limits of their scalability. Mobile networks are already changing to IPv6-only APNs; reachability of IPv4-only destinations from these mobile network is through 6-4 NAT gateways, which sometimes causes problems. Client uptake of IPv6 is progressing steadily. Google reports 49% of clients connecting to its services over IPv6 globally, with France leading at 80%. IPv6 client access measured by Google: Meanwhile, countries around the world are requiring IPv6 reachability for public web services. Examples are the United States, European Union member states among which the Netherlands and Norway, and India, and Japan. IPv6 adoption per country measured by Google: Entities needing to comply with these mandates are looking at Azure's networking capabilities for solutions. Azure supports IPv6 for both private and public networking, and capabilities have developed and expanded over time. This article discusses strategies to build and deploy IPv6-enabled public, internet-facing applications that are reachable from IPv6(-only) clients. Azure Networking IPv6 capabilities Azure's private networking capabilities center on Virtual Networks (VNETs) and the components that are deployed within. Azure VNETs are IPv4/IPv6 dual stack capable: a VNET must always have IPv4 address space allocated, and can also have IPv6 address space. Virtual machines in a dual stack VNET will have both an IPv4 and an IPv6 address from the VNET range, and can be behind IPv6 capable External- and Internal Load Balancers. VNETs can be connected through VNET peering, which effectively turns the peered VNETs into a single routing domain. It is now possible to peer only the IPv6 address spaces of VNETs, so that the IPv4 space assigned to VNETs can overlap and communication across the peering is over IPv6. The same is true for connectivity to on-premise over ExpressRoute: the Private Peering can be enabled for IPv6 only, so that VNETs in Azure do not have to have unique IPv4 address space assigned, which may be in short supply in an enterprise. Not all internal networking components are IPv6 capable yet. Most notable exceptions are VPN Gateway, Azure Firewall and Virtual WAN; IPv6 compatibility is on the roadmap for these services, but target availability dates have not been communicated. But now let's focus on Azure's externally facing, public, network services. Azure is ready to let customers publish their web applications over IPv6. IPv6 capable externally facing network services include: - Azure Front Door - Application Gateway - External Load Balancer - Public IP addresses and Public IP address prefixes - Azure DNS - Azure DDOS Protection - Traffic Manager - App Service (IPv6 support is in public preview) IPv6 Application Delivery IPv6 Application Delivery refers to the architectures and services that enable your web application to be accessible via IPv6. The goal is to provide an IPv6 address and connectivity for clients, while often continuing to run your application on IPv4 internally. Key benefits of adopting IPv6 in Azure include: ✅ Expanded Client Reach: IPv4-only websites risk being unreachable to IPv6-only networks. By enabling IPv6, you expand your reach into growing mobile and IoT markets that use IPv6 by default. Governments and enterprises increasingly mandate IPv6 support for public-facing services. ✅Address Abundance & No NAT: IPv6 provides a virtually unlimited address pool, mitigating IPv4 exhaustion concerns. This abundance means each service can have its own public IPv6 address, often removing the need for complex NAT schemes. End-to-end addressing can simplify connectivity and troubleshooting. ✅ Dual-Stack Compatibility: Azure supports dual-stack deployments where services listen on both IPv4 and IPv6. This allows a single application instance or endpoint to serve both types of clients seamlessly. Dual-stack ensures you don’t lose any existing IPv4 users while adding IPv6 capability. ✅Performance and Future Services: Some networks and clients might experience better performance over IPv6. Also, being IPv6-ready prepares your architecture for future Azure features and services as IPv6 integration deepens across the platform. General steps to enable IPv6 connectivity for a web application in Azure are: Plan and Enable IPv6 Addressing in Azure: Define an IPv6 address space in your Azure Virtual Network. Azure allows adding IPv6 address space to existing VNETs, making them dual-stack. A /56 segment for the VNET is recommended, /64 segment for subnets are required (Azure requires /64 subnets). If you have existing infrastructure, you might need to create new subnets or migrate resources, especially since older Application Gateway v1 instances cannot simply be “upgraded” to dual-stack. Deploy or Update Frontend Services with IPv6: Choose a suitable Azure service (Application Gateway, External / Global Load Balancer, etc.) and configure it with a public IPv6 address on the frontend. This usually means selecting *Dual Stack* configuration so the service gets both an IPv4 and IPv6 public IP. For instance, when creating an Application Gateway v2, you would specify IP address type: DualStack (IPv4 & IPv6). Azure Front Door by default provides dual-stack capabilities with its global endpoints. Configure Backends and Routing: Usually your backend servers or services will remain on IPv4. At the time of writing this in October 2025, Azure Application Gateway does not support IPv6 for backend pool addresses. This is fine because the frontend terminates the IPv6 network connection from the client, and the backend initiates an IPv4 connection to the backend pool or origin. Ensure that your load balancing rules, listener configurations, and health probes are all set up to route traffic to these backends. Both IPv4 and IPv6 frontend listeners can share the same backend pool. Azure Front Door does support IPv6 origins. Update DNS Records: Publish a DNS AAAA record for your application’s host name, pointing to the new IPv6 address. This step is critical so that IPv6-only clients can discover the IPv6 address of your service. If your service also has an IPv4 address, you will have both A (IPv4) and AAAA (IPv6) records for the same host name. DNS will thus allow clients of either IP family to connect. (In multi-region scenarios using Traffic Manager or Front Door, DNS configuration might be handled through those services as discussed later). Test IPv6 Connectivity: Once set up, test from an IPv6-enabled network or use online tools to ensure the site is reachable via IPv6. Azure’s services like Application Gateway and Front Door will handle the dual-stack routing, but it’s good to verify that content loads on an IPv6-only connection and that SSL certificates, etc., work over IPv6 as they do for IPv4. Next, we explore specific Azure services and architectures for IPv6 web delivery in detail. External Load Balancer - single region Azure External Load Balancer (also known as Public Load Balancer) can be deployed in a single region to provide IPv6 access to applications running on virtual machines or VM scale sets. External Load Balancer acts as a Layer 4 entry point for IPv6 traffic, distributing connections across backend instances. This scenario is ideal when you have stateless applications or services that do not require Layer 7 features like SSL termination or path-based routing. Key IPv6 Features of External Load Balancer: - Dual-Stack Frontend: Standard Load Balancer supports both IPv4 and IPv6 frontends simultaneously. When configured as dual-stack, the load balancer gets two public IP addresses – one IPv4 and one IPv6 – and can distribute traffic from both IP families to the same backend pool. - Zone-Redundant by Default: Standard Load Balancer is zone-redundant by default, providing high availability across Azure Availability Zones within a region without additional configuration. - IPv6 Frontend Availability: IPv6 support in Standard Load Balancer is available in all Azure regions. Basic Load Balancer does not support IPv6, so you must use Standard SKU. - IPv6 Backend Pool Support: While the frontend accepts IPv6 traffic, the load balancer will not translate IPv6 to IPv4. Backend pool members (VMs) must have private IPv6 addresses. You will need to add private IPv6 addressing to your existing VM IPv4-only infrastructure. This is in contrast to Application Gateway, discussed below, which will terminate inbound IPv6 network sessions and connect to the backend-end over IPv4. - Protocol Support: Supports TCP and UDP load balancing over IPv6, making it suitable for web applications and APIs, but also for non-web TCP- or UDP-based services accessed by IPv6-only clients. To set up an IPv6-capable External Load Balancer in one region, follow this high-level process: Enable IPv6 on the Virtual Network: Ensure the VNET where your backend VMs reside has an IPv6 address space. Add a dual-stack address space to the VNET (e.g., add an IPv6 space like 2001:db8:1234::/56 to complement your existing IPv4 space). Configure subnets that are dual-stack, containing both IPv4 and IPv6 prefixes (/64 for IPv6). Create Standard Load Balancer with IPv6 Frontend: In the Azure Portal, create a new Standard Load Balancer. During creation, configure the frontend IP with both IPv4 and IPv6 public IP addresses. Create or select existing Standard SKU public IP resources – one for IPv4 and one for IPv6. Configure Backend Pool: Add your virtual machines or VM scale set instances to the backend pool. Note that your backend instances will need to have private IPv6 addresses, in addition to IPv4 addresses, to receive inbound IPv6 traffic via the load balancer. Set Up Load Balancing Rules: Create load balancing rules that map frontend ports to backend ports. For web applications, typically map port 80 (HTTP) and 443 (HTTPS) from both the IPv4 and IPv6 frontends to the corresponding backend ports. Configure health probes to ensure only healthy instances receive traffic. Configure Network Security Groups: Ensure an NSG is present on the backend VM's subnet, allowing inbound traffic from the internet to the port(s) of the web application. Inbound traffic is "secure by default" meaning that inbound connectivity from internet is blocked unless there is an NSG present that explicitly allows it. DNS Configuration: Create DNS records for your application: an A record pointing to the IPv4 address and an AAAA record pointing to the IPv6 address of the load balancer frontend. Outcome: In this single-region scenario, IPv6-only clients will resolve your application's hostname to an IPv6 address and connect to the External Load Balancer over IPv6. Example: Consider a web application running on a VM (or a VM scale set) behind an External Load Balancer in Sweden Central. The VM runs the Azure Region and Client IP Viewer containerized application exposed on port 80, which displays the region the VM is deployed in and the calling client's IP address. The load balancer's front-end IPv6 address has a DNS name of ipv6webapp-elb-swedencentral.swedencentral.cloudapp.azure.com. When called from a client with an IPv6 address, the application shows its region and the client's address. Limitations & Considerations: - Standard SKU Required: Basic Load Balancer does not support IPv6. You must use Standard Load Balancer. - Layer 4 Only: Unlike Application Gateway, External Load Balancer operates at Layer 4 (transport layer). It cannot perform SSL termination, cookie-based session affinity, or path-based routing. If you need these features, consider Application Gateway instead. - Dual stack IPv4/IPv6 Backend required: Backend pool members must have private IPv6 addresses to receive inbound IPv6 traffic via the load balancer. The load balancer does not translate between the IPv6 frontend and an IPv4 backend. - Outbound Connectivity: If your backend VMs need outbound internet access over IPv6, you need to configure an IPv6 outbound rule. Global Load Balancer - multi-region Azure Global Load Balancer (aka Cross-Region Load Balancer) provides a cloud-native global network load balancing solution for distributing traffic across multiple Azure regions. Unlike DNS-based solutions, Global Load Balancer uses anycast IP addressing to automatically route clients to the nearest healthy regional deployment through Microsoft's global network. Key Features of Global Load Balancer: - Static Anycast Global IP: Global Load Balancer provides a single static public IP address (both IPv4 and IPv6 supported) that is advertised from all Microsoft WAN edge nodes globally. This anycast address ensures clients always connect to the nearest available Microsoft edge node without requiring DNS resolution. - Geo-Proximity Routing: The geo-proximity load-balancing algorithm minimizes latency by directing traffic to the nearest region where the backend is deployed. Unlike DNS-based routing, there's no DNS lookup delay - clients connect directly to the anycast IP and are immediately routed to the best region. - Layer 4 Pass-Through: Global Load Balancer operates as a Layer 4 pass-through network load balancer, preserving the original client IP address (including IPv6 addresses) for backend applications to use in their logic. - Regional Redundancy: If one region fails, traffic is automatically routed to the next closest healthy regional load balancer within seconds, providing instant global failover without DNS propagation delays. Architecture Overview: Global Load Balancer sits in front of multiple regional Standard Load Balancers, each deployed in different Azure regions. Each regional load balancer serves a local deployment of your application with IPv6 frontends. The global load balancer provides a single anycast IP address that clients worldwide can use to access your application, with automatic routing to the nearest healthy region. Multi-Region Deployment Steps: Deploy Regional Load Balancers: Create Standard External Load Balancers in multiple Azure regions (e.g. Sweden Central, East US2). Configure each with dual-stack frontends (IPv4 and IPv6 public IPs) and connect them to regional VM deployments or VM scale sets running your application. Configure Global Frontend IP address: Create a Global tier public IPv6 address for the frontend, in one of the supported Global Load Balancer home regions . This becomes your application's global anycast address. Create Global Load Balancer: Deploy the Global Load Balancer in the same home region. The home region is where the global load balancer resource is deployed - it doesn't affect traffic routing. Add Regional Backends: Configure the backend pool of the Global Load Balancer to include your regional Standard Load Balancers. Each regional load balancer becomes an endpoint in the global backend pool. The global load balancer automatically monitors the health of each regional endpoint. Set Up Load Balancing Rules: Create load balancing rules mapping frontend ports to backend ports. For web applications, typically map port 80 (HTTP) and 443 (HTTPS). The backend port on the global load balancer must match the frontend port of the regional load balancers. Configure Health Probes: Global Load Balancer automatically monitors the health of regional load balancers every 5 seconds. If a regional load balancer's availability drops to 0, it is automatically removed from rotation, and traffic is redirected to other healthy regions. DNS Configuration: Create DNS records pointing to the global load balancer's anycast IP addresses. Create both A (IPv4) and AAAA (IPv6) records for your application's hostname pointing to the global load balancer's static IPs. Outcome: IPv6 clients connecting to your application's hostname will resolve to the global load balancer's anycast IPv6 address. When they connect to this address, the Microsoft global network infrastructure automatically routes their connection to the nearest participating Azure region. The regional load balancer then distributes the traffic across local backend instances. If that region becomes unavailable, subsequent connections are automatically routed to the next nearest healthy region. Example: Our web application, which displays the region it is in, and the calling client's IP address, now runs on VMs behind External Load Balancers in Sweden Central and East US2. The External Load Balancer's front-ends are in the backend pool of a Global Load Balancer, which has a Global tier front-end IPv6 address. The front-end has an FQDN of `ipv6webapp-glb.eastus2.cloudapp.azure.com` (the region designation `eastus2` in the FQDN refers to the Global Load Balancer's "home region", into which the Global tier public IP must be deployed). When called from a client in Europe, Global Load Balancer directs the request to the instance deployed in Sweden Central. When called from a client in the US, Global Load Balancer directs the request to the instance deployed in US East 2. Features: - Client IP Preservation: The original IPv6 client address is preserved and available to backend applications, enabling IP-based logic and compliance requirements. - Floating IP Support: Configure floating IP at the global level for advanced networking scenarios requiring direct server return or high availability clustering. - Instant Scaling: Add or remove regional deployments behind the global endpoint without service interruption, enabling dynamic scaling for traffic events. - Multiple Protocol Support: Supports both TCP and UDP traffic distribution across regions, suitable for various application types beyond web services. Limitations & Considerations: - Home Region Requirement: Global Load Balancer can only be deployed in specific home regions, though this doesn't affect traffic routing performance. - Public Frontend Only: Global Load Balancer currently supports only public frontends - internal/private global load balancing is not available. - Standard Load Balancer Backends: Backend pool can only contain Standard Load Balancers, not Basic Load Balancers or other resource types. - Same IP Version Requirement: NAT64 translation isn't supported - frontend and backend must use the same IP version (IPv4 or IPv6). - Port Consistency: Backend port on global load balancer must match the frontend port of regional load balancers for proper traffic flow. - Health Probe Dependencies: Regional load balancers must have proper health probes configured for the global load balancer to accurately assess regional health. Comparison with DNS-Based Solutions: Unlike Traffic Manager or other DNS-based global load balancing solutions, Global Load Balancer provides: - Instant Failover: No DNS TTL delays - failover happens within seconds at the network level. - True Anycast: Single IP address that works globally without client-side DNS resolution. - Consistent Performance: Geo-proximity routing through Microsoft's backbone network ensures optimal paths. - Simplified Management: No DNS record management or TTL considerations. This architecture delivers global high availability and optimal performance for IPv6 applications through anycast routing, making it a good solution for latency-sensitive applications requiring worldwide accessibility with near-instant regional failover. Application Gateway - single region Azure Application Gateway can be deployed in a single region to provide IPv6 access to applications in that region. Application Gateway acts as the entry point for IPv6 traffic, terminating HTTP/S from IPv6 clients and forwarding to backend servers over IPv4. This scenario works well when your web application is served from one Azure region and you want to enable IPv6 connectivity for it. Key IPv6 Features of Application Gateway (v2 SKU): - Dual-Stack Frontend: Application Gateway v2 supports both [IPv4 and IPv6 frontends](https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-faq). When configured as dual-stack, the gateway gets two IP addresses – one IPv4 and one IPv6 – and can listen on both. (IPv6-only is not supported; IPv4 is always paired). IPv6 support requires Application Gateway v2, v1 does not support IPv6. - No IPv6 on Backends: The backend pool must use IPv4 addresses. IPv6 addresses for backend servers are currently not supported. This means your web servers can remain on IPv4 internal addresses, simplifying adoption because you only enable IPv6 on the frontend. - WAF Support: The Application Gateway Web Application Firewall (WAF) will inspect IPv6 client traffic just as it does IPv4. Single Region Deployment Steps: To set up an IPv6-capable Application Gateway in one region, consider the following high-level process: Enable IPv6 on the Virtual Network: Ensure the region’s VNET where the Application Gateway will reside has an IPv6 address space. Configure a subnet for the Application Gateway that is dual-stack (contains both an IPv4 subnet prefix and an IPv6 /64 prefix). Deploy Application Gateway (v2) with Dual Stack Frontend: Create a new Application Gateway using the Standard_v2 or WAF_v2 SKU. Populate Backend Pool: Ensure your backend pool (the target application servers or service) contains (DNS names pointing to) IPv4 addresses of your actual web servers. IPv6 addresses are not supported for backends. Configure Listeners and Rules: Set up listeners on the Application Gateway for your site. When creating an HTTP(S) listener, you choose which frontend IP to use – you would create one listener for IPv4 address and one for IPv6. Both listeners can use the same domain name (hostname) and the same underlying routing rule to your backend pool. Testing and DNS: After the gateway is deployed and configured, note the IPv6 address of the frontend (you can find it in the Gateway’s overview or in the associated Public IP resource). Update your application’s DNS records: create an AAAA record pointing to this IPv6 address (and update the A record to point to the IPv4 if it changed). With DNS in place, test the application by accessing it from an IPv6-enabled client or tool. Outcome: In this single-region scenario, IPv6-only clients will resolve your website’s hostname to an IPv6 address and connect to the Application Gateway over IPv6. The Application Gateway then handles the traffic and forwards it to your application over IPv4 internally. From the user perspective, the service now appears natively on IPv6. Importantly, this does not require any changes to the web servers, which can continue using IPv4. Application Gateway will include the source IPv6 address in an X-Forwarded-For header, so that the backend application has visibility of the originating client's address. Example: Our web application, which displays the region it is deployed in and the calling client's IP address, now runs on a VM behind Application Gateway in Sweden Central. The front-end has an FQDN of `ipv6webapp-appgw-swedencentral.swedencentral.cloudapp.azure.com`. Application Gateway terminates the IPv6 connection from the client and proxies the traffic to the application over IPv4. The client's IPv6 address is passed in the X-Forwarded-For header, which is read and displayed by the application. Calling the application's API endpoint at `/api/region` shows additional detail, including the IPv4 address of the Application Gateway instance that initiates the connection to the backend, and the original client IPv6 address (with the source port number appended) preserved in the X-Forwarded-For header. { "region": "SwedenCentral", "clientIp": "2001:1c04:3404:9500:fd9b:58f4:1fb2:db21:60769", "xForwardedFor": "2001:1c04:3404:9500:fd9b:58f4:1fb2:db21:60769", "remoteAddress": "::ffff:10.1.0.4", "isPrivateIP": false, "expressIp": "2001:1c04:3404:9500:fd9b:58f4:1fb2:db21:60769", "connectionInfo": { "remoteAddress": "::ffff:10.1.0.4", "remoteFamily": "IPv6", "localAddress": "::ffff:10.1.1.68", "localPort": 80 }, "allHeaders": { "x-forwarded-for": "2001:1c04:3404:9500:fd9b:58f4:1fb2:db21:60769" }, "deploymentAdvice": "Public IP detected successfully" } Limitations & Considerations: - Application Gateway v1 SKUs are not supported for IPv6. If you have an older deployment on v1, you’ll need to migrate to v2. - IPv6-only Application Gateway is not allowed. You must have IPv4 alongside IPv6 (the service must be dual-stack). This is usually fine, as dual-stack ensures all clients are covered. - No IPv6 backend addresses: The backend pool must have IPv4 addresses. - Management and Monitoring: Application Gateway logs traffic from IPv6 clients to Log Analytics (the client IP field will show IPv6 addresses). - Security: Azure’s infrastructure provides basic DDoS protection for IPv6 endpoints just as for IPv4. However, it is highly recommended to deploy Azure DDoS Protection Standard: this provides enhanced mitigation tailored to your specific deployment. Consider using the Web Application Firewall function for protection against application layer attacks. Application Gateway - multi-region Mission-critical web applications should be deploy in multiple Azure regions, achieving higher availability and lower latency for users worldwide. In a multi-region scenario, you need a mechanism to direct IPv6 client traffic to the “nearest” or healthiest region. Azure Application Gateway by itself is a regional service, so to use it in multiple regions, we use Azure Traffic Manager for global DNS load balancing, or use Azure Front Door (covered in the next section) as an alternative. This section focuses on the Traffic Manager + Application Gateway approach to multi-region IPv6 delivery. Azure Traffic Manager is a DNS-based load balancer that can distribute traffic across endpoints in different regions. It works by responding to DNS queries with the appropriate endpoint FQDN or IP, based on the routing method (Performance, Priority, Geographic) configured. Traffic Manager is agnostic to the IP version: it either returns CNAMEs, or AAAA records for IPv6 endpoints and A records for IPv4. This makes it suitable for routing IPv6 traffic globally. Architecture Overview: Each region has its own dual-stack Application Gateway. Traffic Manager is configured with an endpoint entry for each region’s gateway. The application’s FQDN is now a domain name hosted by Traffic Manager such as ipv6webapp.traffimanager.net, or a CNAME that ultimately points to it. DNS resolution will go through Traffic Manager, which decides which regional gateway’s FQDN to return. The client then connects directly to that Application Gateway’s IPv6 address, as follows: 1. DNS query: Client asks for ipv6webapp.trafficmanager.net, which is hosted in a Traffic Manager profile. 2. Traffic Manager decision: Traffic Manager sees an incoming DNS request and chooses the best endpoint (say, Sweden Central) based on routing rules (e.g., geographic proximity or lowest latency). 3. Traffic Manager response: Traffic Manager returns the FQDN of the Sweden Central Application Gateway to the client. 4. DNS Resolution: The client resolves regional FQDN and receives a AAAA response containing the IPv6 address. 5. Client connects: The client’s browser connects to the West Europe App Gateway IPv6 address directly. The HTTP/S session is established via IPv6 to that regional gateway, which then handles the request. 6. Failover: If that region becomes unavailable, Traffic Manager’s health checks will detect it and subsequent DNS queries will be answered with the FQDN of the secondary region’s gateway. Deployment Steps for Multi-Region with Traffic Manager: Set up Dual-Stack Application Gateways in each region: Similar to the single-region case, deploy an Azure Application Gateway v2 in each desired region (e.g., one in North America, one in Europe). Configure the web application in each region, these should be parallel deployments serving the same content. Configure a Traffic Manager Profile: In Azure Traffic Manager, create a profile and choose a routing method (such as Performance for nearest region routing, or Priority for primary/backup failover). Add endpoints for each region. Since our endpoints are Azure services with IPs, we can either use Azure endpoints (if the Application Gateways have Azure-provided DNS names) or External endpoints using the IP addresses. The simplest way is to use the Public IP resource of each Application Gateway as an Azure endpoint – ensure each App Gateway’s public IP has a DNS label (so it has a FQDN). Traffic Manager will detect those and also be aware of their IPs. Alternatively, use the IPv6 address as an External endpoint directly. Traffic Manager allows IPv6 addresses and will return AAAA records for them. DNS Setup: Traffic Manager profiles have a FQDN (like ipv6webapp.trafficmanager.net). You can either use that as your service’s CNAME, or you can configure your custom domain to CNAME to the Traffic Manager profile. Health Probing: Traffic Manager continuously checks the health of endpoints. When endpoints are Azure App Gateways, it uses HTTP/S probes to a specified URI path, to each gateway’s address. Make sure each App Gateway has a listener on the probing endpoint (e.g., a health check page) and that health probes are enabled. Testing Failover and Distribution: Test the setup by querying DNS from different geographical locations (to see if you get the nearest region’s IP). Also simulate a region down (stop the App Gateway or backend) and observe if Traffic Manager directs traffic to the other region. Because DNS TTLs are involved, failover isn’t instant but typically within a couple of minutes depending on TTL and probe interval. Considerations in this Architecture: - Latency vs Failover: Traffic Manager as a DNS load balancer directs users at connect time, but once a client has an answer (IP address), it keeps sending to that address until the DNS record TTL expires and it re-resolves. This is fine for most web apps. Ensure the TTL in the Traffic Manager profile is not too high (the default is 30 seconds). - IPv6 DNS and Connectivity: Confirm that each region’s IPv6 address is correctly configured and reachable globally. Azure’s public IPv6 addresses are globally routable. Traffic Manager itself is a global service and fully supports IPv6 in its decision-making. - Cost: Using multiple Application Gateways and Traffic Manager incurs costs for each component (App Gateway is per hour + capacity unit, Traffic Manager per million DNS queries). This is a trade-off for high availability. - Alternative: Azure Front Door: Azure Front Door is an alternative to the Traffic Manager + Application Gateway combination. Front Door can automatically handle global routing and failover at layer 7 without DNS-based limitations, offering potentially faster failover. Azure Front Door is discussed in the next section. In summary, a multi-region IPv6 web delivery with Application Gateways uses Traffic Manager for global DNS load balancing. Traffic Manager will seamlessly return IPv6 addresses for IPv6 clients, ensuring that no matter where an IPv6-only client is, they get pointed to the nearest available regional deployment of your app. This design achieves global resiliency (withstand a regional outage) and low latency access, leveraging IPv6 connectivity on each regional endpoint. Example: The global FQDN of our application is now ipv6webapp.trafficmanager.net and clients will use this FQDN to access the application regardless of their geographical location. Traffic Manager will return the FQDN of one of the regional deployments, `ipv6webapp-appgw-swedencentral.swedencentral.cloudapp.azure.com` or `ipv6webappr2-appgw-eastus2.eastus2.cloudapp.azure.com` depending on the routing method configured, the health state of the regional endpoints and the client's location. Then the client resolves the regional FQDN through its local DNS server and connects to the regional instance of the application. DNS resolution from a client in Europe: Resolve-DnsName ipv6webapp.trafficmanager.net Name Type TTL Section NameHost ---- ---- --- ------- -------- ipv6webapp.trafficmanager.net CNAME 59 Answer ipv6webapp-appgw-swedencentral.swedencentral.cloudapp.azure.com Name : ipv6webapp-appgw-swedencentral.swedencentral.cloudapp.azure.com QueryType : AAAA TTL : 10 Section : Answer IP6Address : 2603:1020:1001:25::168 And from a client in the US: Resolve-DnsName ipv6webapp.trafficmanager.net Name Type TTL Section NameHost ---- ---- --- ------- -------- ipv6webapp.trafficmanager.net CNAME 60 Answer ipv6webappr2-appgw-eastus2.eastus2.cloudapp.azure.com Name : ipv6webappr2-appgw-eastus2.eastus2.cloudapp.azure.com QueryType : AAAA TTL : 10 Section : Answer IP6Address : 2603:1030:403:17::5b0 Azure Front Door Azure Front Door is an application delivery network with built-in CDN, SSL offload, WAF, and routing capabilities. It provides a single, unified frontend distributed across Microsoft’s edge network. Azure Front Door natively supports IPv6 connectivity. For applications that have users worldwide, Front Door offers advantages: - Global Anycast Endpoint: Provides anycast IPv4 and IPv6 addresses, advertised out of all edge locations, with automatic A and AAAA DNS record support. - IPv4 and IPv6 origin support: Azure Front Door supports both IPv4 and IPv6 origins (i.e. backends), both within Azure and externally (i.e. accessible over the internet). - Simplified DNS: Custom domains can be mapped using CNAME records. - Layer-7 Routing: Supports path-based routing and automatic backend health detection. - Edge Security: Includes DDoS protection and optional WAF integration. Front Door enables "cross-IP version" scenario's: a client can connect to the Front Door front-end over IPv6, and then Front Door can connect to an IPv4 origin. Conversely, an IPv4-only client can retrieve content from an IPv6 backend via Front Door. Front Door preserves the client's source IP address in the X-Forwarded-For header. Note: Front Door provides managed IPv6 addresses that are not customer-owned resources. Custom domains should use CNAME records pointing to the Front Door hostname rather than direct IP address references. Private Link Integration Azure Front Door Premium introduces Private Link integration, enabling secure, private connectivity between Front Door and backend resources, without exposing them to the public internet. When Private Link is enabled, Azure Front Door establishes a private endpoint within a Microsoft-managed virtual network. This endpoint acts as a secure bridge between Front Door’s global edge network and your origin resources, such as Azure App Service, Azure Storage, Application Gateway, or workloads behind an internal load balancer. Traffic from end users still enters through Front Door’s globally distributed POPs, benefiting from features like SSL offload, caching, and WAF protection. However, instead of routing to your origin over public, internet-facing, endpoints, Front Door uses the private Microsoft backbone to reach the private endpoint. This ensures that all traffic between Front Door and your origin remains isolated from external networks. The private endpoint connection requires approval from the origin resource owner, adding an extra layer of control. Once approved, the origin can restrict public access entirely, enforcing that all traffic flows through Private Link. Private Link integration brings following benefits: - Enhanced Security: By removing public exposure of backend services, Private Link significantly reduces the risk of DDoS attacks, data exfiltration, and unauthorized access. - Compliance and Governance: Many regulatory frameworks mandate private connectivity for sensitive workloads. Private Link helps meet these requirements without sacrificing global availability. - Performance and Reliability: Traffic between Front Door and your origin travels over Microsoft’s high-speed backbone network, delivering low latency and consistent performance compared to public internet paths. - Defense in Depth: Combined with Web Application Firewall (WAF), TLS encryption, and DDoS protection, Private Link strengthens your security posture across multiple layers. - Isolation and Control: Resource owners maintain control over connection approvals, ensuring that only authorized Front Door profiles can access the origin. - Integration with Hybrid Architectures: For scenarios involving AKS clusters, custom APIs, or workloads behind internal load balancers, Private Link enables secure connectivity without requiring public IPs or complex VPN setups. Private Link transforms Azure Front Door from a global entry point into a fully private delivery mechanism for your applications, aligning with modern security principles and enterprise compliance needs. Example: Our application is now placed behind Azure Front Door. We are combining a public backend endpoint and Private Link integration, to show both in action in a single example. The Sweden Central origin endpoint is the public IPv6 endpoint of the regional External Load Balancers and the origin in US East 2 is connected via Private Link integration The global FQDN `ipv6webapp-d4f4euhnb8fge4ce.b01.azurefd.net` and clients will use this FQDN to access the application regardless of their geographical location. The FQDN resolves to Front Door's global anycast address, and the internet will route client requests to the nearest Microsoft edge from this address is advertised. Front Door will then transparently route the request to the nearest origin deployment in Azure. Although public endpoints are used in this example, that traffic will be route over the Microsoft network. From a client in Europe: Calling the application's api endpoint on `ipv6webapp-d4f4euhnb8fge4ce.b01.azurefd.net/api/region` shows some more detail. { "region": "SwedenCentral", "clientIp": "2001:1c04:3404:9500:fd9b:58f4:1fb2:db21", "xForwardedFor": "2001:1c04:3404:9500:fd9b:58f4:1fb2:db21", "remoteAddress": "2a01:111:2053:d801:0:afd:ad4:1b28", "isPrivateIP": false, "expressIp": "2001:1c04:3404:9500:fd9b:58f4:1fb2:db21", "connectionInfo": { "remoteAddress": "2a01:111:2053:d801:0:afd:ad4:1b28", "remoteFamily": "IPv6", "localAddress": "2001:db8:1:1::4", "localPort": 80 }, "allHeaders": { "x-forwarded-for": "2001:1c04:3404:9500:fd9b:58f4:1fb2:db21", "x-azure-clientip": "2001:1c04:3404:9500:fd9b:58f4:1fb2:db21" }, "deploymentAdvice": "Public IP detected successfully" } "remoteAddress": "2a01:111:2053:d801:0:afd:ad4:1b28" is the address from which Front Door sources its request to the origin. From a client in the US: The detailed view shows that the IP address calling the backend instance now is local VNET address. Private Link sources traffic coming in from a local address taken from the VNET it is in. The original client IP address is again preserved in the X-Forwarded-For header. { "region": "eastus2", "clientIp": "2603:1030:501:23::68:55658", "xForwardedFor": "2603:1030:501:23::68:55658", "remoteAddress": "::ffff:10.2.1.5", "isPrivateIP": false, "expressIp": "2603:1030:501:23::68:55658", "connectionInfo": { "remoteAddress": "::ffff:10.2.1.5", "remoteFamily": "IPv6", "localAddress": "::ffff:10.2.2.68", "localPort": 80 }, "allHeaders": { "x-forwarded-for": "2603:1030:501:23::68:55658" }, "deploymentAdvice": "Public IP detected successfully" } Conclusion IPv6 adoption for web applications is no longer optional. It is essential as public IPv4 address space is depleted, mobile networks increasingly use IPv6 only and governments mandate IPv6 reachability for public services. Azure's comprehensive dual-stack networking capabilities provide a clear path forward, enabling organizations to leverage IPv6 externally without sacrificing IPv4 compatibility or requiring complete infrastructure overhauls. Azure's externally facing services — including Application Gateway, External Load Balancer, Global Load Balancer, and Front Door — support IPv6 frontends, while Application Gateway and Front Door maintain IPv4 backend connectivity. This architecture allows applications to remain unchanged while instantly becoming accessible to IPv6-only clients. For single-region deployments, Application Gateway offers layer-7 features like SSL termination and WAF protection. External Load Balancer provides high-performance layer-4 distribution. Multi-region scenarios benefit from Traffic Manager's DNS-based routing combined with regional Application Gateways, or the superior performance and failover capabilities of Global Load Balancer's anycast addressing. Azure Front Door provides global IPv6 delivery with edge optimization, built-in security, and seamless failover across Microsoft's network. Private Link integration allows secure global IPv6 distribution while maintaining backend isolation. The transition to IPv6 application delivery on Azure is straightforward: enable dual-stack addressing on virtual networks, configure IPv6 frontends on load balancing services, and update DNS records. With Application Gateway or Front Door, backend applications require no modifications. These Azure services handle the IPv4-to-IPv6 translation seamlessly. This approach ensures both immediate IPv6 accessibility and long-term architectural flexibility as IPv6 adoption accelerates globally.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.
Accelerate designing, troubleshooting & securing your network with Gen-AI powered tools, now GA.
We are thrilled to announce the general availability of Azure Networking skills in Copilot, an extension of Copilot in Azure and Security Copilot designed to enhance cloud networking experience. Azure Networking Copilot is set to transform how organizations design, operate, and optimize their Azure Network by providing contextualized responses tailored to networking-specific scenarios and using your network topology.Unmasking DDoS Attacks (Part 1/3)
In today’s always-online world, we take uninterrupted access to websites, apps, and digital services for granted. But lurking in the background is a cyber threat that can grind everything to a halt in an instant: DDoS attacks. These attacks don’t sneak in to steal data or plant malware—they’re all about chaos and disruption, flooding servers with so much traffic that they crash, slow down, or completely shut off. Over the years, DDoS attacks have evolved from annoying nuisances to full-blown cyber weapons, capable of hitting massive scales—some even reaching terabit-level traffic. Companies have lost millions of dollars due to downtime, and even governments and critical infrastructure have been targeted. Whether you’re a CTO, a business owner, a security pro, or just someone who loves tech, understanding these attacks is key to stopping them before they cause real damage. That’s where this blog series comes in. We’ll be breaking down everything you need to know about DDoS attacks—how they work, real-world examples, the latest prevention strategies, and even how you can leverage Azure services to detect and defend against them. This will be a three-part series, covering: 🔹Unmasking DDoS Attacks (Part 1): Understanding the Fundamentals and the Attacker’s Playbook What exactly is a DDoS attack, and how does an attacker plan and execute one? In this post, we’ll cover the fundamentals of DDoS attacks, explore the attacker’s perspective, and break down how an attack is crafted and launched. We’ll also discuss the different categories of DDoS attacks and how attackers choose which strategy to use. 🔹 Unmasking DDoS Attacks (Part 2): Analyzing Known Attack Patterns & Lessons from History DDoS attacks come in many forms, but what are the most common and dangerous attack patterns? In this deep dive, we’ll explore real-world DDoS attack patterns, categorize them based on their impact, and analyze some of the largest and most disruptive DDoS attacks in history. By learning from past attacks, we can better understand how DDoS threats evolve and what security teams can do to prepare. 🔹 Unmasking DDoS Attacks (Part 3): Detection, Mitigation, and the Future of DDoS Defense How do you detect a DDoS attack before it causes damage, and what are the best strategies to mitigate one? In this final post, we’ll explore detection techniques, proactive defense strategies, and real-time mitigation approaches. We’ll also discuss future trends in DDoS attacks and evolving defense mechanisms, ensuring that businesses stay ahead of the ever-changing threat landscape. So, without further ado, let’s jump right into Part 1 and start unraveling the world of DDoS attacks. What is a DDoS Attack? A Denial-of-Service (DoS) attack is like an internet traffic jam, but on purpose. It’s when attackers flood a website or online service with so much junk traffic that it slows down, crashes, or becomes completely unreachable for real users. Back in the early days of the internet, pulling off a DoS attack was relatively simple. Servers were smaller, and a single computer (or maybe a handful) could send enough malicious requests to take down a website. But as technology advanced and cloud computing took over, that approach stopped being effective. Today’s online services run on massive, distributed cloud networks, making them way more resilient. So, what did attackers do? They leveled up. Instead of relying on just one machine, they started using hundreds, thousands, or even millions—all spread out across the internet. These attacks became "distributed", with waves of traffic coming from multiple sources at once. And that’s how DDoS (Distributed Denial-of-Service) attacks were born. Instead of a single attacker, imagine a botnet—an army of compromised devices (anything from hacked computers to unsecured IoT gadgets)—all working together to flood a target with traffic. The result? Even the most powerful servers can struggle to stay online. In short, a DDoS attack is just a bigger, badder version of a DoS attack, built for the modern internet. And with cloud computing making things harder to take down, attackers have only gotten more creative in their methods. An Evolving Threat Landscape As recently reported by Microsoft: “DDoS attacks are happening more frequently and on a larger scale than ever before. In fact, the world has seen almost a 300 percent increase in these types of attacks year over year, and it’s only expected to get worse [link]". Orchestrating large-scale DDoS botnets attacks are inexpensive for attackers and are often powered by leveraging compromised devices (i.e., security cameras, home routers, cable modems, IoT devices, etc.). Within the last 6 months alone, our competitors have reported the following: June 2023: Waves of L7 attacks on various Microsoft properties March 2023: Akamai – 900 Gbps DDoS Attack Feb 2023: Cloudflare mitigates record-breaking 71 million request-per-second DDoS attack August 2022: How Google Cloud blocked the largest Layer 7 DDoS attack at 46 million rps Graphs below are F5 labs report. Figure 1 Recent trends indicate that Technology sector is one of the most targeted segments along with Finance and Government Figure 2 Attacks are evolving & a large % of attacks are upgrading to Application DDoS or a multi-vector attack As the DDoS attacks gets bigger and more sophisticated, we need to take a defense-in-depth approach, to protect our customers in every step of the way. Azure services like Azure Front Door, Azure WAF and Azure DDoS are all working on various strategies to counter these emerging DDoS attack patterns. We will cover more on how to effectively use these services to protect your services hosted on Azure in part-3. Understanding DDoS Attacks: The Attacker's Perspective There can be many motivations behind a DDoS attack, ranging from simple mischief to financial gain, political activism, or even cyber warfare. But launching a successful DDoS attack isn’t just about flooding a website with traffic—it requires careful planning, multiple test runs, and a deep understanding of how the target’s infrastructure operates. So, what does it actually mean to bring down a service? It means pushing one or more critical resources past their breaking point—until the system grinds to a halt, becomes unresponsive, or outright collapses under the pressure. Whether it’s choking the network, exhausting compute power, or overloading application processes, the goal is simple: make the service so overwhelmed that legitimate users can’t access it at all. Resources Targeted During an Attack Network Capacity (Bandwidth and Infrastructure): The most common resource targeted in a DDoS attack, the goal is to consume all available network capacity, thereby preventing legitimate requests from getting through. This includes overwhelming routers, switches, and firewalls with excessive traffic, causing them to fail. Processing Power: By inundating a server with more requests than it can process, an attacker can cause it to slow down or even crash, denying service to legitimate users. Memory: Attackers might attempt to exhaust the server's memory capacity, causing degradation in service or outright failure. Disk Space and I/O Operations: An attacker could aim to consume the server's storage capacity or overwhelm its disk I/O operations, resulting in slowed system performance or denial of service. Connection-based Resources: In this type of attack, the resources that manage connections, such as sockets, ports, file descriptors, and connection tables in networking devices, are targeted. Overwhelming these resources can cause a disruption of service for legitimate users. Application Functionality: Specific functions of a web application can be targeted to cause a denial of service. For instance, if a web application has a particularly resource-intensive operation, an attacker may repeatedly request this operation to exhaust the server's resources. DNS Servers: A DNS server can be targeted to disrupt the resolution of domain names to IP addresses, effectively making the web services inaccessible to users. Zero-Day Vulnerabilities: Attackers often exploit unknown or zero-day vulnerabilities in applications or the network infrastructure as part of their attack strategy. Since these vulnerabilities are not yet known to the vendor, no patch is available, making them an attractive target for attackers. CDN Cache Bypass – HTTP flood attack bypasses the web application caching system that helps manage server load. Crafting The Attack Plan Most modern services no longer run on a single machine in someone’s basement—they are hosted on cloud providers with auto-scaling capabilities and vast network capacity. While this makes them more resilient, it does not make them invulnerable. Auto-scaling has its limits, and cloud networks are shared among millions of customers, meaning attackers can still find ways to overwhelm them. When planning a DDoS attack, attackers first analyze the target’s infrastructure to identify potential weaknesses. They then select an attack strategy designed to exploit those weak points as efficiently as possible. Different DDoS attack types target different resources and have unique characteristics. Broadly, these attack strategies can be categorized into three main types: Volumetric Attacks For volumetric attacks, the attacker’s goal is to saturate the target’s system resources by generating a high volume of traffic. To weaponize this attack, attackers usually employ botnets or compromised systems or even use other cloud providers (paid or fraudulently) to generate a large volume of traffic. The traffic is directed towards the target's network, making it difficult for legitimate traffic to reach the services. Examples: SYN Flood, UDP Flood, ICMP Flood, DNS Flood, HTTP Flood. Amplification Attacks Amplification attacks are a cunning tactic where attackers seek to maximize the impact of their actions without expending significant resources. Through crafty exploitation of vulnerabilities or features in systems, such as using reflection-based methods or taking advantage of application-level weaknesses, they make small queries or requests that produce disproportionately large responses or resource consumption on the target's side. Examples: DNS Amplification, NTP Amplification, Memcached Reflection Low and Slow Attacks Non-volumetric exhaustion attacks focus on depleting specific resources within a system or network rather than inundating it with sheer volume of traffic. By exploiting inherent limitations or design aspects, these attacks selectively target elements such as connection tables, CPU, or memory, leading to resource exhaustion without the need for high volume of traffic, making this a very attractive strategy for attackers. Attacks, such as Slowloris and RUDY, subtly deplete server resources like connections or CPU by mimicking legitimate traffic, making them difficult to detect. Examples: Slowloris, R-U-Dead-Yet? (RUDY). Vulnerability-Based Attacks Instead of relying on sheer traffic volume, these attacks exploit known vulnerabilities in software or services. The goal isn’t just to overwhelm resources but to crash, freeze, or destabilize a system by taking advantage of flaws in how it processes certain inputs. This type of attack is arguably the hardest to craft because it requires deep knowledge of the technology stack a service is running on. Attackers must painstakingly research software versions, configurations, and known vulnerabilities, then carefully craft malicious “poison pill” requests designed to trigger a failure. It’s a game of trial and error, often requiring multiple test runs before finding a request that successfully brings down the system. It’s also one of the most difficult attacks to defend against. Unlike volumetric attacks, which flood a service with traffic that security tools can detect, a vulnerability-based attack can cause a software crash so severe that it prevents the system from even generating logs or attack traffic metrics. Without visibility into what happened, detection and mitigation become incredibly challenging. Examples: Apache Killer, Log4Shell Executing The Attack Now that an attacker has finalized their attack strategy and identified which resource(s) to exhaust, they still need a way to execute the attack. They need the right tools and infrastructure to generate the overwhelming force required to bring a target down. Attackers have multiple options depending on their technical skills, resources, and objectives: Booters & Stressers – Renting attack power from popular botnets. Amplification attacks – Leveraging publicly available services (like DNS or NTP servers) to amplify attack traffic. Cloud abuse – Hijacking cloud VMs or misusing free-tier compute resources to generate attacks. But when it comes to executing large-scale, persistent, and devastating DDoS attacks, one method stands above the rest: botnets. Botnets: The Powerhouse Behind Modern DDoS Attacks A botnet is a network of compromised devices—computers, IoT gadgets, cloud servers, and even smartphones—all controlled by an attacker. These infected devices (known as bots or zombies) remain unnoticed by their owners while quietly waiting for attack commands. Botnets revolutionized DDoS attacks, making them: Massive in scale – Some botnets include millions of infected devices, generating terabits of attack traffic. Hard to block – Since the traffic comes from real, infected machines, it’s difficult to filter out malicious requests. Resilient – Even if some bots are shut down, the remaining network continues the attack. But how do attackers build, control, and launch a botnet-driven DDoS attack? The secret lies in Command and Control (C2) systems. How a Botnet Works: Inside the Attacker’s Playbook Infecting Devices: Building the Army Attackers spread malware through phishing emails, malicious downloads, unsecured APIs, or IoT vulnerabilities. Once infected, a device becomes a bot, silently connecting to the botnet's network. IoT devices (smart cameras, routers, smart TVs) are especially vulnerable due to poor security. Command & Control (C2) – The Brain of the Botnet A botnet needs a Command & Control (C2) server, which acts as its central command center. The attacker sends instructions through the C2 server, telling bots when, where, and how to attack. Types of C2 models: Centralized C2 – A single server controls all bots (easier to attack but simpler to manage). Peer-to-Peer (P2P) C2 – Bots communicate among themselves, making takedowns much harder. Fast Flux C2 – C2 infrastructure constantly changes IP addresses to avoid detection. Launching the Attack: Overwhelming the Target When the attacker gives the signal, the botnet unleashes the attack. Bots flood the target with traffic, connection requests, or amplification exploits. Since the traffic comes from thousands of real, infected devices, distinguishing attackers from normal users is extremely difficult. Botnets use encryption, proxy networks, and C2 obfuscation to stay online. Some botnets use hijacked cloud servers to further hide their origins. Famous Botnets & Their Impact Mirai (2016) – One of the most infamous botnets, Mirai infected IoT devices to launch a 1.2 Tbps DDoS attack, taking down Dyn DNS and causing major outages across Twitter, Netflix, and Reddit. Mozi (2020-Present) – A peer-to-peer botnet with millions of IoT bots worldwide. Meris (2021) – Hit 2.5 million RPS (requests per second), setting records for application-layer attacks. Botnets have transformed DDoS attacks, making them larger, harder to stop, and widely available on the dark web. With billions of internet-connected devices, botnets are only growing in size and sophistication. We will cover strategies on botnet detection and mitigations employed by Azure Front Door and Azure WAF services against such large DDoS attacks. Wrapping Up Part-1 With that, we’ve come to the end of Part 1 of our Unmasking DDoS Attacks series. To summarize, we’ve covered: ✅ The fundamentals of DDoS attacks—what they are and why they’re dangerous. ✅ The different categories of DDoS attacks—understanding how they overwhelm resources. ✅ The attacker’s perspective—how DDoS attacks are planned, strategized, and executed. ✅ The role of botnets—why they are the most powerful tool for large-scale attacks. This foundational knowledge is critical to understanding the bigger picture of DDoS threats—but there’s still more to uncover. Stay tuned for Part 2, where we’ll dive deeper into well-known DDoS attack patterns, examine some of the biggest DDoS incidents in history, and explore what lessons we can learn from past attacks to better prepare for the future. See you in Part 2!Revolutionizing hyperscale application delivery and security: The New Azure Front Door edge platform
In this introductory blog to the new Azure Front Door next generation platform, we will go over the motivations, design choices and learnings from this undertaking which helped us successfully achieve massive gains in scalability, security and resiliency.
Prohibiting Domain Fronting with Azure Front Door and Azure CDN Standard from Microsoft (classic)
Azure Front Door and Azure CDN Standard from Microsoft (classic) are postponing the domain fronting blocking enforcement to January 22, 2024, and will add two log fields to help you check if your resources display domain fronting behavior by December 25, 2023.
