- 28 Oct, 2025
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- 3 Mins Read
Understanding Azure Load Balancer
In modern cloud infrastructures, application availability and performance are critical. Whether you’re hosting a web app, database service, or API backend, evenly distributing incoming network traffic helps ensure reliability and scalability.
This is where Azure Load Balancer comes in — a robust, Layer 4 (TCP/UDP) load-balancing service offered by Microsoft Azure that automatically distributes traffic across healthy virtual machines (VMs) or services within a region.
What is Azure Load Balancer?
Azure Load Balancer is a fully managed, high-performance load-balancing solution that operates at the transport layer (Layer 4) of the OSI model. It ensures no single server becomes overwhelmed with requests by distributing network traffic across multiple backend resources such as VMs, Virtual Machine Scale Sets, or availability sets.
It supports both inbound and outbound scenarios, making it ideal for:
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Distributing internet traffic to internal Azure resources
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Balancing internal network traffic
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Managing outbound connections to the internet
Types of Azure Load Balancers
Azure offers two main types of Load Balancers based on visibility and use cases:
1. Public Load Balancer
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Routes traffic from the internet to Azure VMs using public IP addresses.
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Used when you need to expose your application or service to external users.
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Ideal for web applications, API gateways, or internet-facing services.
2. Internal (Private) Load Balancer
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Used within a virtual network (VNet) to distribute traffic among internal Azure resources.
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Does not expose public endpoints.
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Suitable for database clusters, internal APIs, or backend services.
Key Components of Azure Load Balancer
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Frontend IP Configuration – Defines the public or private IP that receives incoming traffic.
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Backend Pool – A collection of virtual machines or services that receive the distributed traffic.
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Health Probes – Continuously check the health status of each VM in the backend pool to ensure only healthy instances handle traffic.
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Load Balancing Rules – Define how traffic is distributed, including protocol, port, and session persistence.
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Inbound NAT Rules – Map specific ports of the Load Balancer to individual backend instances for direct access (e.g., SSH or RDP).
How Azure Load Balancer Works
Here’s a simplified flow of how Azure Load Balancer operates:
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A client sends a request to the Load Balancer’s frontend IP.
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The Load Balancer checks for a load-balancing rule that matches the request.
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A health probe determines which backend VM instances are available.
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The request is forwarded to one of the healthy VMs using a hashing algorithm that considers source IP, destination IP, and port.
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The response is sent back through the Load Balancer to the client.
This process ensures even traffic distribution and automatic failover in case of backend failure.
Benefits of Using Azure Load Balancer
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⚡ High Availability: Distributes traffic among healthy instances to eliminate single points of failure.
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📈 Scalability: Automatically scales with traffic without manual intervention.
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🔒 Security: Works seamlessly with Network Security Groups (NSGs) and Azure Firewall.
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🕒 Low Latency: Built into Azure’s global network for high throughput and minimal latency.
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💰 Cost-Effective: Azure Load Balancer is free for inbound load balancing within a region. You only pay for the outbound data processed.
Common Use Cases
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Balancing traffic for web applications hosted on multiple VMs.
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Providing redundancy for backend services within a virtual network.
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Managing outbound connectivity for VMs in private subnets.
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Distributing load among multiple application tiers in multi-region deployments.
Comparison: Azure Load Balancer vs Application Gateway
| Feature | Azure Load Balancer | Azure Application Gateway |
|---|---|---|
| OSI Layer | Layer 4 (TCP/UDP) | Layer 7 (HTTP/HTTPS) |
| Traffic Type | Network traffic | Web traffic |
| SSL Termination | ❌ No | ✅ Yes |
| URL-based Routing | ❌ No | ✅ Yes |
| Health Probes | TCP/HTTP | HTTP/HTTPS |
| Use Case | VM traffic distribution | Web app routing and security |
If your application needs content-based routing (e.g., path-based, header-based), go with Application Gateway.
If you need simple, high-performance load distribution, use Azure Load Balancer.
Final Thoughts
The Azure Load Balancer is a core component in designing highly available and scalable applications on Microsoft Azure. Its simplicity, performance, and deep integration with other Azure services make it an essential tool for cloud architects and DBAs alike.
Azure Load Balancer is not just a “nice-to-have” it’s an essential building block for any resilient and scalable architecture in Azure. It provides the foundational layer of traffic distribution that your more complex services are built upon.
Whether you’re running a simple two-VM setup or a massive, globally distributed application, understanding and leveraging the power of the Azure Load Balancer is a critical step on your cloud journey.
Ready to try it? Head over to the Azure Portal and create your first load balancer today!
At Learnomate Technologies, we help professionals and organizations master cloud technologies like Azure, AWS, and Oracle Cloud — enabling efficient and reliable infrastructure management.