You`ve recently migrated an application from a customer`s on-premise data center to the AWS cloud. Currently, you`re using the ELB to serve traffic to the legacy application. The ELB is also using HTTP port 80 as the health check ping port. The application is currently responding by returning a text file on port 80 when you test the IP address directly. However, the instance is not registering as healthy even though the appropriate amount of time has passed for the health check to register as healthy. How might the issue be resolved? Choose the correct answer from the options below

Answer options:

A.Change the ELB listener port from ping port 80 to HTTPS port 80 for the instance to register as healthy
B.Change the ELB listener port from HTTP port 80 to TCP port 80 for the instance to register as healthy
C.Change the ELB listener port from HTTP port 80 to HTTPS port 80 for the instance to register as healthy
D.Change the ELB listener port from HTTP port 80 to TCP port 443 for the instance to register as healthy

Answer – B
Since the application is a custom application and not a standard HTTP application, hence you need to have the TCP ports open.
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