How to set Network Load Balancer as a target of Application Load Balancer ?
Tags: aws, learning, cloudskills
Published: 2023-06-26 11:26:29

Load balancers are essential in the realm of cloud architecture and networking because they effectively distribute traffic and guarantee high availability. The Application Load Balancer (ALB) and Network Load Balancer (NLB) stand out among the well-liked load balancing choices offered by Amazon Web Services (AWS) for their distinctive features. Though occasionally we require the finest of both worlds? We will go into the complexities of linking an ALB to an NLB as well as the interesting world of load balancing in this blog post.

**What is ALB and NLB?**

The term "ALB" refers to the load-balancing service offered by Amazon Web Services (AWS), also known as ALB. It runs at Layer 7 of the OSI model, the application layer, and is made to distribute incoming traffic to a variety of targets, including EC2 instances, containers, and Lambda functions, using sophisticated routing and load balancing algorithms. ALBs are a good choice for applications requiring sophisticated routing and traffic management capabilities because they offer cutting-edge features like content-based routing, path-based routing, SSL termination, and cookie-based session affinity.

Network Load Balancer, or NLB, is another load balancing service provided by AWS. The main duty of NLBs, which function at Layer 4's transport layer, is to split up incoming TCP and UDP traffic among many targets. They are the best choice for applications that need extremely high performance and low latency because they are highly scalable and able to handle millions of requests per second. NLBs are a good choice for high-volume, stateless applications that need effective traffic distribution because they provide capabilities including TCP and UDP load balancing, cross-zone load balancing, and support for static IP addresses.

Both ALBs and NLBs are part of the Elastic Load Balancing (ELB) service in AWS and serve as key components in building resilient, scalable, and highly available architectures in the cloud.


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There are numerous entities in the load balancing landscape that can act as target groups for load balancers. IP addresses, instances, Application Load Balancers (ALBs), and Lambda functions are examples of these entities. Network load balancers (NLBs), however, cannot be directly joined as target groups of any load balancer. This is a notable exception. While NLBs are made to handle TCP and UDP traffic at the transport layer, IP addresses, instances, ALBs, and Lambda functions may all be smoothly integrated into load balancing configurations. So they operate at a lower level and are mostly in charge of forwarding traffic to destinations like EC2 instances, containers, and IP addresses. NLBs are a special part of load balancing designs because of this differentiation, although they cannot act as direct target groups for other load balancers.

Setting up the NLB with numerous instances is the first step in using it as a target group for the application load balancer (ALB). NLBs are well known for their capacity to manage heavy transport layer traffic, which makes them the best option for distributing TCP and UDP traffic across numerous targets. Our applications' scalability and availability can be ensured by establishing the NLB with numerous instances. This stage establishes the groundwork for creating a secure link between the NLB and ALB, allowing the NLB to benefit from the ALB's strong traffic management features while the ALB offers cutting-edge application-layer features to improve the delivery of our applications.

	The Application Load Balancer (ALB) will be hosted in a particular subnet in the second stage, creating a regulated network environment for its operation. We will choose the utilize IP addresses option while setting up the target group for the ALB. The Network Load Balancer (NLB) is utilized in this situation. We may extract the private IP address of the NLB from the elastic interface connected to the NLB as the NLB is already configured with its target instances. The ALB can send traffic to the NLB by using this private IP address as its target audience. The NLB then distributes the traffic to the appropriate instances with which it is linked.  We provide efficient load balancing by coupling the ALB and NLB in this way, utilizing the special properties of both types of load balancers.
	
In conclusion, a Network Load Balancer (NLB) and an Application Load Balancer (ALB) connection offers the chance to maximize the combined power of both load balancing technologies. We may use NLBs' high-performance transport layer capabilities in conjunction with ALBs' cutting-edge application-layer characteristics, despite the fact that they cannot directly be used as target groups for other load balancers. We create a seamless connection that improves scalability, availability, and traffic management by setting up the NLB with many instances and configuring the ALB to use the private IP address of the NLB as the target group. With the help of this integration, experts in cloud infrastructure may create reliable and effective load balancing designs that meet the needs of various applications and deliver top performance.  We discover the possibility for seamless scalability and efficient application delivery in the always changing world of cloud networking by delving into the complexities of linking ALB to NLB.