Azure Load Balancer

As explained in Microsoft Azure in Action

Azure Load Balancer is a managed Azure service that distributes network traffic across backend resources according to configured rules and health status.

When an application gets more traffic than one virtual machine (VM) can handle, Azure Load Balancer provides one entry point and distributes incoming requests across VMs in a backend pool. Rules determine where traffic goes; a health probe helps keep requests flowing to VMs that are ready to serve them. section 4.5 section 4.5.5

It also helps with outages. If a frontend VM stops responding, traffic can go to the remaining healthy VMs—but only if there are other VMs available. In a multi-region design, Azure Traffic Manager handles routing between regions, while Load Balancer distributes traffic among VMs within a region. section 1.2.3

The main decisions are:

• Choose the right routing service. Azure Load Balancer distributes TCP or UDP traffic; unlike Azure Application Gateway, it does not route by requested web address. It offers higher performance and lower latency than Application Gateway for the load-balancing role. section 3.3.4
• Provide multiple VMs in a backend pool. A load balancer cannot spread requests across machines that are not there. section 4.5 section 4.6
• Bring together a frontend IP configuration, backend pool, health probe, and load-balancing rule to define the service. section 4.5.5

A growing web application

An alpaca-shearing site has outgrown its single VM. With the frontend IP, backend pool, probe, and rule configured, PowerShell can create its Standard Load Balancer using New-AzLoadBalancer and the parameters -FrontendIpConfiguration, -BackendAddressPool, -Probe, and -LoadBalancingRule. Visitors use the shared entry point; the service passes their requests to backend VMs. section 4.5 section 4.5.5

Figure 1.6 Redundant Azure architecture example. This setup uses Azure Traffic Manager to route requests between regions, ensuring availability if one region goes offline. Within each region, an Azure Load Balancer directs traffic to healthy VMs, while multiple VMs prevent single points of failure. Azure SQL Database is replicated between regions to keep data consistent, so the application remains available and up to date even during outages.

See how Load Balancer fits inside a broader availability design: it directs traffic to healthy VMs within each region, while Traffic Manager routes between regions. section 1.2.3

How Microsoft Azure in Action covers it

How deep it goes

Explains the entry point, backend pool, rules, and health probe, then shows their assembly with a PowerShell cmdlet.

Examples

Uses a growing alpaca-shearing application, a redundant multi-region architecture, and a New-AzLoadBalancer PowerShell command.

What it assumes

Introduces load balancing through a single-VM traffic problem and assumes multiple VMs are available for distribution.

What you can do after

Apply it via PowerShell by combining a frontend IP configuration, backend pool, health probe, and load-balancing rule.

How it connects

Connects virtual machines, backend pools, health probes, Azure Application Gateway, and Azure Traffic Manager to traffic distribution and availability.

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Related concepts

• Azure Application Gatewayalternative to · Azure Application Gateway is a managed Azure application-delivery service that provides Layer 7 load balancing and HTTP-based routing to backend resources.
• load balancingused by · Load balancing is the distribution of requests or computational work across multiple resources to manage demand, reduce workload imbalance, and improve utilization or availability.
• public ip addressuses · A public IPv4 address is a globally unique IPv4 network address routable on the public Internet and assigned to an internet-facing resource.
• virtual machineuses · A virtual machine is a software-based environment that emulates or implements an abstract computer system, providing an interface on which an operating system or programs can execute.

This explainer was generated by Manning's knowledge graph from the text of Microsoft Azure in Action. The section links point to the parts of the book it draws on.