Load Balancer Listeners

5 minutes 5 Questions

Listeners are components of Elastic Load Balancers that take incoming requests and distribute them to one or more registered backend instances. They are configured with a protocol and port number for incoming connections, along with a default rule defining how to route requests to target instances. Listeners support various protocols such as HTTP, HTTPS, TCP, and TLS. They process incoming connections and establish sessions or connections to the appropriate target instance based on the configured routing rules.

Guide to Load Balancer Listeners

What it is: A Listener in Load Balancing is a process that checks for connection requests. It is configured with a protocol and a port for front-end (client to load balancer) and backend (load balancer to back-end instances) connections. The common protocols include HTTP, HTTPS, TCP, and SSL.

Why it is Important: Load Balancer Listeners allow the Load Balancer to distribute the incoming traffic evenly across multiple target instances, which enhances the performance and fault tolerance of your applications.

How it Works: When a client sends a request, the listener checks the load balancer for connection requests from clients using the specified protocol and port. Once a request is received, it decides where to route the request based on the configured load balancing algorithm.

Exam Tips: Understanding how Load Balancer Listeners work is fundamental in Exam. You should be aware of the different types of listeners, their protocols, and how they operate. Note that you may encounter questions about the routing algorithm, ensuring that the listener is configured correctly for the type of connection and traffic you expect to manage, and the implications of these configurations on the performance and reliability of your applications.

Answering Questions on Load Balancer Listeners: 1. Understand the different types of Load Balancers and their corresponding listeners 2. Familiarize yourself with the effects of different configurations on application performance and reliability 3. Be able to explain how a listener routes traffic to target instances 4. Understand the function of health checks in conjunction with Load Balancer listeners.

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Question 1

Your company has a critical application using an Application Load Balancer to handle the traffic. Security recently detected potential attack incidents, which may cause the Load Balancer to start misbehaving. Which security feature should you enable to reduce the likelihood of such incidents?

Disable the existing Listener, and create a new Listener. Enable AWS WAF on the Application Load Balancer. Enable Amazon GuardDuty on the Application Load Balancer. Configure Direct Connect for the Application Load Balancer.

Correct Answer: Enable AWS WAF on the Application Load Balancer.

AWS WAF (Web Application Firewall) is designed to protect applications from common web exploits such as XSS or SQLi attacks. Enabling WAF on an Application Load Balancer allows you to add a security layer that monitors and mitigates potential attacks, which helps to reduce the likelihood of Load Balancer misbehaving.

Question 2

You have a Classic Load Balancer with two listener configurations; one is TCP port 80 and the other is HTTPS port 443. How can you achieve SSL offloading in this case?

Create the listener with HTTPS as the protocol for the frontend and HTTPS for the backend on port 443. Create the listener with HTTPS as the protocol for the frontend and HTTP for the backend on port 443. Create the listener with HTTP as the protocol for the frontend and HTTP for the backend on port 80. Create the listener with TCP as the protocol for the frontend and HTTP for the backend on port 443.

Correct Answer: Create the listener with HTTPS as the protocol for the frontend and HTTP for the backend on port 443.

To achieve SSL offloading, you need to configure the listener with HTTPS as the protocol for the frontend and HTTP for the backend on port 443. This offloads the SSL decryption tasks from the instances to the Load Balancer, which reduces the workload on instances and helps improve performance.

Question 3

You have recently migrated your application to AWS, and it's now using an Application Load Balancer for distributing incoming client requests. Your application has dynamic content and requires a sticky session. What action should you take?

Add a sticky session to your instances. Enable the stickiness on your ALB target group. Add a latency metric to your ALB Listener. Enable cross-zone load balancing.

Correct Answer: Enable the stickiness on your ALB target group.

To have a sticky session using an Application Load Balancer, enabling stickiness on target groups is necessary. ALB supports sticky sessions by attaching a cookie to each request directed towards target group, ensuring that a specific target instance handles future requests initiated by the user.

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