Azure Nwtworking Blog > Build scalable cross-subscription applications with Azure Load Balancer
We are thrilled to announce that Azure cross-subscription Load Balancer is now available for public preview in all Azure public and national cloud regions. This capability enables you to have your Azure Load Balancer components in different subscriptions. For example, you could have the load balancer’s frontend or backend instances in a different subscription from the one that the load balancer belongs to.
The matrix below shows some of the scenarios that cross-subscription load balancing enables:
Subscription 1 | Subscription 2 |
Load Balancer | Backend pool resources and Frontend IP address |
Load Balancer and Backend pool resources | Frontend IP address |
Load Balancer and Frontend IP address | Backend pool resources |
Key Features
Cross-subscription Frontends
With cross-subscription frontends, the IP address in the configuration can belong to a different subscription than the one of the load balancer. This feature applies to both public and internal frontends.
- For public load balancer, each public IP address can have a different subscription.
- For internal frontends, each frontend configuration has to be in the same virtual network (VNet) that the internal load balancer is connected to.
Cross-subscription Backends
With cross-subscription backends, the backend pool of the load balancer can include backend instances from another subscription.
Regional Load Balancer
Regional load balancers can now reference a VNet that belongs to another subscription, and instances within that VNet can attach to the load balancer’s backend pool. Like internal frontends, every backend pool must use the same VNet.
The new syncMode property on the backend pool of the regional load balancer enables cross-subscription load balancing. This property must be set on when configuring the backend pool, and it has two possible values: Automatic or Manual.
Global Load Balancer
The backend pool of a global load balancer can also contain cross-subscription instances. With this feature, regional load balancers that connect to the global load balancer can be in different subscriptions. Each regional load balancer can be in a separate subscription. Note, cross-subscription frontends cannot be used with global load balancers.
Examples of real world scenarios
To illustrate the benefits of Azure’s cross-subscription Load Balancer, let’s look at two sample customer situations. In this situation, we’ll find out about the customers, their needs, and how Azure Load Balancer solved them.
Who is Contoso1?
Contoso1 is a large financial service company based out of Asia. Contoso1 is currently migrating their services to Azure from on-prem. Their primary application is a payment processing service on which their end users can complete transactions between other users.
This service has specific requirements that need to be fulfilled as part of the migration to Azure.
What are the customer’s requirements?
As part of the customer’s migration to Azure they were searching for a traffic distribution solution that would meet the following requirements:
- Their application will be replicated across multiple regions, Contoso1 needs a traffic distribution solution that could load balance traffic globally
- Further, each replica will be hosted in its own subscription.
- Because of how the customer’s application works, it is critical to have ultra-low latency traffic distribution
- A single entry point into the application with seamless scale up/down
- As the customer adds/removes regional deployment, their end users should see zero interruption.
- As mentioned above, each replica will be deployed in its own subscription. A traffic distrubtion solution needs to have the ability to load balance across multiple subscriptions.
How did Azure’s cross-subscription Load Balancer help Contoso1?
Given the requirements outlined above, the customer was onboarded to the cross-subscription feature of Azure global Load Balancer. With Azure global load balancer, customers can load balance traffic across multiple regions with ultra-low latency. In addition, customers get a single static IP address and can scale backend regional load balancers up or down with no interruption to end users.
Given that global load balancer now supports cross-subscription backends, Contoso1 can meet the requirements for their application. The customer added each regional load balancer to the backend pool of their global load balancer seamlessly and successfully migrate their application to Azure.
Who is Contoso2?
Contoso2 is a North American retail company that has experienced rapid growth in the past few years. As they expand their business, they have been using Azure to scale up their operations and meet their customer needs.
What are the issues with the customer’s current set-up?
Contoso2 has been using one tenant and subscription for all their resources, but this is not working well for their growing needs. They are reaching the maximum number of resources per subscription, and they are having trouble organizing their resources within the single subscription. This is creating problems for managing their resources and fulfilling their end users’ expectations.
How did Azure help Contoso2?
To support their growth, Contoso2 has been collaborating with Azure to redesign their workloads across multiple subscriptions. By distributing their applications and resources across multiple subscriptions, Contoso2 can enhance resource management and avoid hitting subscription-based resource limits for their applications.
As part of their transition to multiple subscription, Contoso2 required the capability to connect cross-subscription resources to their load balancers. For instance, IP addresses in subscription A need to be connected to load balancers in subscription B. To help achieve this requirement, the customer was onboarded to the cross-subscription feature of Azure Load Balancer. With the cross-subscription load balancer, the Contoso2 could easily connect cross-subscription resources to their load balancer and fulfill all of the Contoso2’s requirements.
Get started with cross-subscription load balancing
Visit the cross-subscription load balancer overview to learn more about cross-subscription load balancing and how it can fit into your architecture.
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