Azure Load Balancer: Features, Pricing, and Best Practices

What Is Azure Load Balancer? 

The Azure Load Balancer is a cloud networking service developed by Microsoft, aimed at improving the performance and availability of your applications. It works by distributing network traffic across multiple servers in the Azure cloud.

The Azure Load Balancer is a layer-4 (Transport Layer) load balancer, meaning it operates at the TCP and UDP protocol level. This allows it to handle a range of scenarios, from simple web applications to complex, multi-tier architectures spanning numerous virtual machines.

The Azure Load Balancer is offered in three service tiers:

  • Standard Load Balancer: Routes traffic within and across regions, supports high performance and low latency.
  • Gateway Load Balancer: A virtual appliance that supports service-chaining scenarios such as data analytics.
  • Basic Load Balancer: Suitable for smaller applications that don’t need high availability or redundancy.

This is part of a series of articles about Azure automation.

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Benefits of Using Azure Load Balancer 

Enhanced Availability and Resilience

By distributing incoming traffic across multiple servers, Azure Load Balancer ensures that no single server becomes a bottleneck, thereby preventing server overloads.

The Azure Load Balancer automatically detects and reroutes traffic away from unhealthy or non-responsive servers. It also supports zone-redundant and cross-region load balancing, to further increase application availability. By distributing traffic across servers in different zones or regions, it safeguards your applications against zone or region-specific failures.

Scalability to Manage High Traffic Loads

The Azure Load Balancer is not just about maintaining application performance; it’s also about scaling it. As your business grows and your traffic increases, the Azure Load Balancer helps you scale to accommodate the additional load.

By spreading the load across multiple servers, it ensures your applications can keep up with the increased demand without experiencing performance degradation. Furthermore, the Azure Load Balancer’s support for autoscaling allows it to automatically adjust as the number of servers is scaled up or down, based on current traffic loads.

Learn more in our detailed guide to Azure autoscaling 

Built-In Network Security and Protection

Another benefit of the Azure Load Balancer is its built-in network security and protection features. By providing inbound and outbound network address translation (NAT), it shields your virtual machines from direct exposure to the internet, thereby enhancing their security.

Moreover, the Azure Load Balancer’s support for DDoS protection and firewall integration further bolsters your network’s security. These features help to safeguard your applications against malicious attacks and unauthorized access.

Integration with Azure Services and Resources

The Azure Load Balancer integrates with Azure Virtual Machines, Azure App Service, and Azure Kubernetes Service, to optimize the performance and scalability of applications running on these services. Similarly, you can integrate it with Azure Monitor and Azure Security Center to gain insights into your network’s performance and security.

Azure Load Balancer Features and Capabilities 

Here are the main features provided by Azure Load Balancer:

Load Balancing Rules

Load balancing rules define how the load balancer should distribute incoming traffic among the backend servers.

You can configure these rules based on various parameters, such as the source and destination IP address, source and destination port, and the transport protocol (TCP or UDP). This flexibility allows you to tailor the load balancing behavior to your specific needs.

Health Probes

Azure Load Balancer provides health probes, which continuously monitor the health and availability of your backend servers. They help the load balancer make informed decisions about traffic distribution.

If a health probe detects that a server is unhealthy or non-responsive, the load balancer automatically stops sending traffic to that server until it becomes healthy again. This feature ensures your applications remain available and responsive, even in the event of server failures.

Backend Pools

Backend pools are groups of virtual machines that receive inbound network traffic from the Load Balancer. This feature allows you to distribute traffic across multiple servers, ensuring a smooth and seamless user experience. With backend pools, you can scale your applications and manage traffic, while ensuring high availability for your services.

Session Persistence

Session persistence ensures that client connections are routed to the same server for the duration of a session. It’s a crucial capability for applications that maintain state information on the server side. With session persistence, you can maintain a consistent user experience and avoid unnecessary disruptions.

Connection Reuse

Connection reuse allows a load balancer to reuse an existing connection to a backend pool without having to establish a new one. It not only reduces the overhead of connection establishment but also improves performance and efficiency.

Azure Load Balancer Deployment Topologies 

Azure Load Balancer can be deployed in two different topologies:

  • A public load balancer provides outbound connections for virtual machines (VMs) in a virtual network. Connections are achieved by translating private IP addresses to public IP addresses. This is used to load-balance ingress internet traffic flowing to your VMs.
  • An internal load balancer is used where private IPs are only needed by the front end of your application. An internal load balancer can load-balance traffic inside a virtual network. If you have a hybrid cloud, the load balancer frontend can also be accessed from your on-premises network.

Azure Load Balancer Pricing

Basic Load Balancer

The Basic Load Balancer is a cost-effective solution designed for applications that don’t require advanced features. It provides load balancing for up to 300 instances, and it supports inbound and outbound scenarios. It also comes with a built-in health probe, which automatically checks the health of your servers and reroutes traffic if a server is down.

The Basic Load Balancer is included for free with your Azure subscription, so you only pay for the virtual machines that you use. This makes it a cost-effective solution for small businesses or projects with a tight budget.

Standard Load Balancer

The Standard Load Balancer is a more advanced solution designed for larger, more complex applications. It supports up to 1000 instances, and it provides additional features such as zone-redundancy, private IP addresses, and HA ports.

The pricing for the Standard Load Balancer is based on a pay-as-you-go model. You pay for each hour that the Load Balancer is running, and the price varies depending on the region. However, the price generally ranges from $0.025 to $0.08 per hour.

Gateway Load Balancer

Gateway Load Balancer. This is a specialized solution designed for managing network traffic between your on-premise network and your Azure virtual network. It provides features such as VPN connectivity, firewall rules, and DDoS protection.

The pricing for the Gateway Load Balancer is also based on a pay-as-you-go model. The price varies depending on the bandwidth and the region, but it generally ranges from $0.01 to $0.013 per hour, with data processed charged at $0.004 per GB. While it’s the most expensive option, it provides a high level of control and security.

Best Practices for Using Azure Load Balancer 

Use Multiple Availability Zones

Azure Load Balancer provides built-in high availability and fault tolerance. To make full use of these capabilities, it’s recommended to distribute your virtual machines (VMs) across multiple availability zones. This helps to ensure that even if one zone experiences an outage, your application remains accessible from the other zones.

Always Configure Network Security Groups (NSGs)

One of the best ways to improve network security in Azure is by using Network Security Groups (NSGs) to control inbound and outbound traffic to your VMs.

NSGs act as a virtual firewall for your VMs, allowing you to define access control rules for your network traffic. By configuring NSGs, you can prevent unauthorized access to your VMs and safeguard your applications from potential threats.

Integrate with Azure DDoS Protection

Another way to enhance security is by integrating Azure Load Balancer with Azure DDoS Protection. This service protects your applications from Distributed Denial of Service (DDoS) attacks, which can cause significant disruption and downtime. Azure DDoS Protection uses advanced algorithms and machine learning to detect and mitigate DDoS attacks in real-time.

Only Create the Minimal Necessary Load Balancing Rules

When configuring Azure Load Balancer, it’s important to only create the necessary rules. This helps to avoid complexity and potential misconfigurations, which can lead to performance issues or security vulnerabilities. The goal is to maintain a balance between security and performance by keeping your configuration simple and streamlined.

Regularly Review Diagnostic Logs

Lastly, it’s crucial to enable and regularly review diagnostic logs. These logs provide valuable insights into your Azure Load Balancer’s operation, helping you detect issues early and troubleshoot them effectively.

In addition, diagnostic logs provide a record of operations and changes, which is useful for auditing purposes. By regularly reviewing these logs, you can ensure your Azure Load Balancer is functioning optimally and maintain a high level of operational transparency.

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