Your company has a set of EC2 instances sitting behind an Elastic Load Balancer. There is a requirement to create an OpsWorks stack to host the newer version of this application. The OpsWorks stack has been created and the current ELB was selected to host the newer version of the application. Now the application is not responding to the requests. What could be the cause?

Answer options:

A.This is because the OpsWorks stack is utilizing the instances of the current application after the ELB was attached to it.
B.You have configured the OpsWorks stack to deploy the instances of the new version of the application in the same domain as that of the old instances.
C.After the ELB is attached to the OpsWorks stack, it would have de-registered the instances of the current application and therefore the current application is not responding to requests.
D.This is because the OpsWorks web layer is utilizing the instances of the current application after the ELB was attached to the OpsWorks layer.

Answer – C
The AWS Documentation mentions the following
If you choose to use an existing Elastic Load Balancing load balancer, you should first confirm that it is not being used for other purposes and has no attached instances. After the load balancer is attached to the layer, OpsWorks removes any existing instances and configures the load balancer to handle only the layer`s instances. Although it is technically possible to use the Elastic Load Balancing console or API to modify a load balancer`s configuration after attaching it to a layer, you should not do so; the changes will not be permanent.
For more information on OpsWorks ELB layers, please visit the below URL:
http://docs.aws.amazon.com/opsworks/latest/userguide/layers-elb.html