You`re consulting for a company that is migrating its legacy application ( built on TCP ) to the AWS cloud. In order to apply high availability, you`ve decided to implement Elastic Load Balancer and Auto Scaling services to serve traffic to this legacy application.

Answer options:

A.Configure the load balancer with the following ports: TCP:80 and TCP:8080 and the instance protocol to TCP:80 and TCP:8080
B.Configure the load balancer with the following ports: HTTP:80 and HTTP:8080 and the instance protocol to HTTPs:80 and HTTPs:8080
C.Configure the load balancer with the following ports: HTTP:80 and HTTP:8080 and the instance protocol to TCP:80 and TCP:8080
D.Configure the load balancer with the following ports: HTTP:80 and HTTP:8080 and the instance protocol to HTTP:80 and HTTP:8080

Answer – A
The application in this scenario is a legacy-based application built on TCP and works on ports 80 and 8080. It requires that the traffic should be routed correctly.
Option A is CORRECT because for the ELB to route the traffic correctly, it should be configured with ports TCP:80 and TCP 8080. For the backends as well, the ports that should be configured must be TCP:80 and TCP:8080.
Options B, C, and D are all incorrect as both the ELB and instance protocol must be configured for ports TCP:80 and TCP:8080.
More information on ELB
Since the application is a custom application and not a standard HTTP application. Hence you need to have the TCP ports open. Hence option A is the right option.
Before you start using Elastic Load Balancing, you must configure one or more listeners for your Classic Load Balancer. A listener is a process that checks for connection requests. It is configured with a protocol and a port for front-end (client to load balancer) connections and a protocol and a port for back-end (load balancer to back-end instance) connections.
Elastic Load Balancing supports the following protocols.
HTTP
HTTPS (secure HTTP)
TCP
SSL (secure TCP)
For more information on listener configuration for ELB, please see the below link.
http://docs.aws.amazon.com/elasticloadbalancing/latest/classic/elb-listener-config.html