Azure Load Balancer

Azure Load Balancer is a highly available, scalable, and customizable Layer-4 load balancer that enables you to distribute incoming traffic across multiple virtual machines (VMs) or instances in a backend pool. It is a cloud-native service offered by Microsoft Azure that is designed to optimize application performance, availability, and resiliency.

Features and Benefits of Azure Load Balancer

Azure Load Balancer comes with a rich set of features and benefits that make it an ideal choice for load balancing in the cloud. Some of the key features and benefits of Azure Load Balancer are:

High Availability

Azure Load Balancer is built to be highly available and resilient. It uses a distributed architecture that enables it to handle high volumes of traffic and provide automatic failover in case of node failures. The load balancer is designed to monitor the health of backend instances and automatically route traffic to healthy instances.

Scalability

Azure Load Balancer is highly scalable, and it can handle millions of requests per second. It supports both inbound and outbound scenarios, and it can be used to load balance traffic across multiple regions or availability zones. It also supports auto-scaling, which enables it to automatically adjust capacity based on demand.

Customization

Azure Load Balancer provides a high degree of customization, allowing you to configure load balancing rules, health probes, session persistence, and other settings based on your specific requirements. It also supports advanced scenarios such as Direct Server Return (DSR), which enables traffic to bypass the load balancer for improved performance.

Security

Azure Load Balancer is designed to be secure, with features such as Network Security Groups (NSGs) and SSL termination. It also supports integration with Azure Active Directory (AAD) and Azure Firewall, which enables you to implement advanced security policies and access controls.

Deployment Models for Azure Load Balancer

Azure Load Balancer supports two deployment models: Basic and Standard.

Basic Load Balancer

Basic Load Balancer is a cost-effective option that provides simple load balancing capabilities for small-scale applications. It supports TCP and UDP load balancing, but it does not support advanced features such as health probes, session persistence, or SSL offloading.

Standard Load Balancer

Standard Load Balancer is a more advanced option that provides a rich set of load balancing features and capabilities. It supports TCP, UDP, and HTTP load balancing, and it includes features such as health probes, session persistence, and SSL offloading. It also supports integration with Azure Traffic Manager, which enables you to implement global load balancing across multiple regions.

Configuration Options for Azure Load Balancer

Azure Load Balancer provides a wide range of configuration options that enable you to customize load balancing based on your specific requirements. Some of the key configuration options include:

Backend Pools

Backend Pools are groups of VMs or instances that you want to load balance traffic across. You can create multiple backend pools and assign different load balancing rules to each pool.

Load Balancing Rules

Load Balancing Rules define how traffic is distributed across backend pools. You can create multiple load balancing rules, each with its own protocol, port, and backend pool configuration.

Health Probes

Health Probes are used to monitor the health of backend instances and ensure that traffic is only routed to healthy instances. You can configure health probes to use TCP, HTTP, or HTTPS protocols, and you can define custom settings such as interval, timeout, and thresholds.

Session Persistence

Session Persistence ensures that client requests are always directed to the same backend instance, which is particularly useful for stateful applications. Azure Load Balancer supports several session persistence options, including source IP affinity, cookie based affinity, and hash-based affinity.

Frontend IP Configurations

Frontend IP Configurations define the public IP address or virtual network (VNet) IP address that the load balancer listens on for incoming traffic. You can configure multiple frontend IP configurations, each with its own protocol and port settings.

Outbound Rules

Outbound Rules define how outbound traffic from backend instances is routed. You can configure outbound rules to use either SNAT (Source Network Address Translation) or DNAT (Destination Network Address Translation) mode.

Public IP Addresses

Azure Load Balancer supports both static and dynamic public IP addresses. You can configure static public IP addresses for the load balancer frontend, or you can use dynamic public IP addresses that are assigned by Azure.

Load Balancing Algorithms

Azure Load Balancer supports several load balancing algorithms, including round-robin, least connections, and source IP hash. You can choose the load balancing algorithm that best suits your application requirements. More details 

SSL Offloading

SSL Offloading is the process of terminating SSL/TLS connections at the load balancer and forwarding decrypted traffic to backend instances. Azure Load Balancer supports SSL offloading for both inbound and outbound traffic.

How to Configure Azure Load Balancer

Configuring Azure Load Balancer involves several steps, including creating a backend pool, defining load balancing rules, configuring health probes, and assigning frontend IP configurations. Here is an overview of the steps involved:

Here is a detailed step-by-step guide on how to configure Azure Load Balancer:

Step 1: Create a Load Balancer Resource

The first step in configuring Azure Load Balancer is to create a load balancer resource. To create a load balancer resource, follow these steps:

1. Open the Azure portal and sign in with your credentials.
2. Click on “Create a resource” and search for “Load Balancer”.
3. Click on “Load Balancer” and then click on “Create”.
4. Fill out the required information, such as the subscription, resource group, and load balancer name.
5. Choose the deployment model and location.
6. Click on “Review + create” to review your settings.
7. Click on “Create” to create the load balancer resource.

Step 2: Configure Frontend IP Addresses and Ports

After creating the load balancer resource, the next step is to configure frontend IP addresses and ports. To configure frontend IP addresses and ports, follow these steps:

1. In the Azure portal, navigate to the load balancer resource that you created.
2. Click on “Frontend IP configurations” under the “Settings” section.
3. Click on “Add” to create a new frontend IP configuration.
4. Fill out the required information, such as the name, IP version, and IP address.
5. Click on “Add” to create the frontend IP configuration.
6. Repeat these steps to add additional frontend IP configurations or ports.

Step 3: Configure Backend Pool and Health Probes

The next step is to configure the backend pool and health probes. To configure the backend pool and health probes, follow these steps:

1. In the Azure portal, navigate to the load balancer resource that you created.
2. Click on “Backend pools” under the “Settings” section.
3. Click on “Add” to create a new backend pool.
4. Fill out the required information, such as the name and the virtual machine that you want to add to the pool.
5. Click on “Add” to create the backend pool.
6. Click on “Health probes” under the “Settings” section.
7. Click on “Add” to create a new health probe.
8. Fill out the required information, such as the name, protocol, and port.
9. Click on “Add” to create the health probe.
10. Associate the health probe with the backend pool that you created.

Step 4: Configure Load Balancing Rules

The final step is to configure the load balancing rules. To configure the load balancing rules, follow these steps:

1. In the Azure portal, navigate to the load balancer resource that you created.
2. Click on “Load balancing rules” under the “Settings” section.
3. Click on “Add” to create a new load balancing rule.
4. Fill out the required information, such as the name, frontend IP configuration, backend pool, and health probe.
5. Choose the load balancing algorithm that you want to use, such as Round Robin or Least Connections.
6. Click on “Add” to create the load balancing rule.
7. Repeat these steps to add additional load balancing rules.

Step 5: Configure NAT rules (Optional)

If you want to enable inbound connectivity to a backend pool behind a load balancer, you can create Network Address Translation (NAT) rules. To configure NAT rules, follow these steps:

1. In the Azure portal, navigate to the load balancer resource that you created.
2. Click on “Inbound NAT rules” under the “Settings” section.
3. Click on “Add” to create a new NAT rule.
4. Fill out the required information, such as the name, frontend IP configuration, protocol, and backend port.
5. Choose the backend pool and the virtual machine that you want to associate with the NAT rule.
6. Click on “Add” to create the NAT rule.
7. Repeat these steps to add additional NAT rules.

Step 6: Configure Inbound and Outbound Network Security Groups (NSGs)

If you want to restrict inbound or outbound traffic to or from the load balancer or backend pool, you can create Network Security Groups (NSGs). To configure NSGs, follow these steps:

1. In the Azure portal, navigate to the load balancer resource that you created.
2. Click on “Inbound security rules” or “Outbound security rules” under the “Settings” section.
3. Click on “Add” to create a new security rule.
4. Fill out the required information, such as the name, source IP address, destination IP address, protocol, and port.
5. Choose the action that you want to take, such as Allow or Deny.
6. Click on “Add” to create the security rule.
7. Repeat these steps to add additional security rules.

Step 7: Test the Load Balancer

After configuring the load balancer, you should test it to ensure that it is working as expected. To test the load balancer, follow these steps:

1. Navigate to the public IP address of the load balancer.
2. Access the application or service that is behind the load balancer.
3. Verify that the requests are being distributed evenly to the backend pool.

Azure load balancer pricing

Azure Load Balancer pricing is based on several factors, including the number of rules, data processing, and data transfer. There are also separate pricing options for inbound and outbound data transfer. Here is an overview of the pricing for Azure Load Balancer:

Inbound Data Transfer

Azure Load Balancer charges for inbound data transfer at a rate of $0.01 per GB. This means that you are charged for data transferred into Azure Load Balancer from the internet or other Azure services.

Outbound Data Transfer

Azure Load Balancer charges for outbound data transfer at a rate of $0.01 per GB for the first 10 TB, and $0.008 per GB for data transfer over 10 TB. This means that you are charged for data transferred out of Azure Load Balancer to the internet or other Azure services.

Load Balancer Rule

Azure Load Balancer charges for each load balancing rule configured on the service. The cost per rule is $0.025 per hour. This means that you are charged for each rule configured on the load balancer.

Data Processing

Azure Load Balancer charges for data processing at a rate of $0.01 per million load balancing operations. This means that you are charged for each operation that Azure Load Balancer performs, such as routing traffic to backend instances or monitoring the health of backend instances.

Public IP Address

Azure Load Balancer charges for public IP addresses assigned to the service. The cost per IP address is $0.005 per hour. This means that you are charged for each public IP address assigned to the load balancer.

Standard vs Basic Tiers

Azure Load Balancer is available in two pricing tiers: Standard and Basic. The Standard tier provides additional features and benefits, such as outbound connections for virtual machines, SSL offloading, and health probes. The Basic tier does not include these features and is designed for basic load balancing requirements.

The pricing for the Standard and Basic tiers varies based on the number of load balancer rules and data processing operations. The Standard tier is priced at a higher rate than the Basic tier.

Conclusion

Azure Load Balancer is a highly scalable, highly available, and customizable load balancing service that is designed to optimize application performance and resiliency in the cloud. It provides a rich set of features and benefits, including high availability, scalability, customization, and security. With its extensive configuration options and deployment models, Azure Load Balancer can be tailored to meet the unique load balancing requirements of your application.