Azure Load Balancer Overview

Azure Load Balancer is a highly available and scalable network load balancing solution that distributes incoming traffic across a pool of backend virtual machines or services. It operates at Layer 4 (TCP/UDP) of the OSI model and provides high availability, fault tolerance, and performance for your applications.

Key Features and Benefits

High Availability: Ensures your application remains available even if individual virtual machines or components fail. Load Balancer health probes monitor the health of backend instances and automatically redirect traffic away from unhealthy ones.
Scalability: Can handle large volumes of network traffic, automatically scaling to meet demand.
Layer 4 Load Balancing: Distributes traffic based on IP address and port, making it suitable for a wide range of TCP and UDP-based applications.
Health Probes: Configurable probes to check the health of backend instances, ensuring traffic is only sent to healthy destinations.
Direct Server Return (DSR): Supports DSR for improved performance in certain scenarios.
Outbound Connectivity: Provides a secure and scalable way for virtual machines to access the internet or other Azure services using a shared public IP address.
Integration: Seamlessly integrates with other Azure services like Virtual Machine Scale Sets, Availability Sets, and Azure Kubernetes Service (AKS).

How it Works

When a client sends a request to your application, the request first hits the Azure Load Balancer. The Load Balancer then examines the request and forwards it to one of the healthy backend instances based on a configured load-balancing rule and algorithm. If a backend instance becomes unhealthy, the health probe detects this, and the Load Balancer stops sending traffic to that instance.

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Global Reach: Azure Load Balancer can distribute traffic across multiple availability zones or even regions for disaster recovery scenarios with Azure Traffic Manager.

Common Use Cases

Distributing incoming web traffic across multiple web servers for high availability and scalability.
Load balancing internal application traffic between different tiers of your application.
Providing outbound internet access for a group of virtual machines using a single public IP.
Ensuring continuous availability of critical services by automatically failing over to healthy instances.

Types of Azure Load Balancers

Azure offers two main types of Load Balancer:

Public Load Balancer: Distributes inbound traffic from the internet to virtual machines within an Azure Virtual Network.
Internal Load Balancer: Distributes inbound traffic from within your virtual network to virtual machines in the same virtual network. This is ideal for line-of-business applications that are not exposed to the internet.

Understanding Azure Load Balancer is crucial for building resilient and scalable applications in Azure. It forms the backbone of many high-availability architectures.

Next Steps:

Explore the different types of Azure Load Balancers and learn how to configure them for your specific needs.