SAA-C03 Question 49
Single answerYour company is hosting a web application on an Amazon EC2 instance in a public subnet. Users report they cannot access the application. Upon investigation, you discover the EC2 instance is running correctly, and the application is listening on port 80. Which configuration change is most likely needed to resolve the issue?
- A
Add an inbound rule to the instance's Security Group to allow traffic on port 80 from 0.0.0.0/0.
- B
Add an outbound rule to the instance's Security Group to allow traffic on port 80 to 0.0.0.0/0.
- C
Create a Network ACL rule to explicitly allow inbound traffic on port 80 from 0.0.0.0/0.
- D
Enable port forwarding in the EC2 instance's operating system to redirect traffic to port 80.
Show answer and explanation
Correct answer: A
Explanation
The issue lies in controlling network traffic to the EC2 instance. Security Groups are stateful, and to allow inbound traffic to the application, an inbound rule for port 80 must be added. This ensures external traffic can reach the web application.
- A. Correct.
This is the correct answer. Security Groups act as virtual firewalls for EC2 instances. To allow external users to access the application on port 80, an inbound rule allowing traffic from 0.0.0.0/0 must be added.
- B. Incorrect.
Outbound rules control traffic leaving the instance. Since the issue involves users accessing the application, outbound rules are not relevant here.
- C. Incorrect.
While Network ACLs can control traffic at the subnet level, they are stateless and not required to resolve this issue as Security Groups are sufficient.
- D. Incorrect.
Port forwarding is unnecessary in this case because the application is already listening on port 80, and the issue is with network access control.