Oracle Cloud Infrastructure 2019 Developer Associate — Question 80

You are in the process of setting up a highly available student registration website on Oracle Cloud Infrastructure (OCI). You use a load balancer and a database service on OCI. You launch two compute instances each in a different subnet and add them to the back end set of a public load balancer. The load balancer is configured correctly and working. You then deploy the student registration application on these two compute instances. The application can communicate with the database service. However, when you type the URL of this student registration application in your browser, no web page appears.
What could be the cause?

Answer options

• A. The security lists of the subnets on which the two instances are located do not have "allow" rules for port 80 and 443.
• B. The load balancer performed a health check on the application and found that compute instances were not in a healthy state and terminated the instances.
• C. The client requested https access to the application and the load balancer service does not support end-to-end SSL from the client to the listener to the back- end set.
• D. The Dynamic Routing Gateway is preventing the client traffic from your data center network from reaching the public IP of the load balancer.

Correct answer: A

Explanation

The correct answer is A because if the security lists do not permit traffic on ports 80 and 443, the application will not be accessible via HTTP or HTTPS. Option B is incorrect as the issue is not related to instance health, and option C is not valid because the load balancer can support SSL. Option D is also incorrect since the Dynamic Routing Gateway is not relevant in this context.