Question on ELBs

[varun-mathur]

Hi Jon,

The answer for an ELB to listen on ports 80 and 8080 is indicated to be a Classic Load Balancer. Unless the customer is constrained to an EC2 classic stack, there should be really no case to use the classic LB. Please advise, the question is:

You are migrating a legacy Java-based web application, which is hosted on the on-premises network, to the AWS cloud. The application is still using TCP which uses both port 80 and 8080. Your manager advised you that these 2 ports are required to be open in order for the legacy application to work properly in your VPC.

Which of the following ELB configuration would you implement to meet the above requirements?

[Jon-Bonso]

Hi Varun,

Thank you for posting your question. I understand that a Classic Load Balancer is, well, “classic” in the sense that it supports the legacy applications for EC2-Classic. It is also important to note that Classic Load Balancers are also suitable if your application is using custom security policies or protocols that are not supported by an Application Load Balancer (such as TCP). I actually still saw a bunch of Classic Load Balancer questions in the official SA Pro exam, which is why we still have this in our practice tests.

In this scenario, the legacy application requires a TCP connection. This can be fulfilled by using a Network Load Balancer (NLB) or a Classic Load Balancer. Again, the Application Load Balancer (ALB) doesn’t support TCP. The option that uses NLB has an incorrect port/protocol configuration, which only leaves us with CLB:

https://aws.amazon.com/elasticloadbalancing/

Let us know if you need further assistance. The Tutorials Dojo team is dedicated to help you pass your AWS exam on your first try!

Regards,

Jon Bonso @ Tutorials Dojo