SOA-C02 Question #493: Real Exam Question with Answer & Explanation

Question

A company has migrated its legacy on-premises web application to an Amazon EC2 instance. The web application requires a single static public IP address to accept traffic and process requests. End users must be able to reach the web application through the example.com domain. A SysOps administrator must implement a solution that maintains the web application with the least amount of effort. Which combination of actions will meet these requirements? (Choose two.)

Options

• AConfigure an Application Load Balancer (ALB). Add the EC2 instance to a target group that is
• BCreate an Amazon Route 53 A record for the associated EC2 IP address.
• CCreate an Amazon Route 53 CNAME record for the associated EC2 IP address.
• DCreate an Elastic IP address, and associate it with the EC2 instance.
• ECreate an Auto Scaling group with a minimum capacity of 1 and a maximum capacity of 2.

Explanation

D solves the core requirement: by default, EC2 public IPs are dynamic and change on every stop/start cycle. An Elastic IP (EIP) is a static IPv4 address that stays associated with your account and instance, satisfying the "single static public IP" requirement. B then wires up DNS - a Route 53 A record maps the domain name example.com directly to that static IPv4 address, so end users can reach the app by name.

Why the others are wrong:

• A (ALB): Load balancers don't have a single static IP by nature (they use dynamic IPs behind a DNS hostname). Adding an ALB for a single EC2 instance also violates the "least effort" constraint.
• C (CNAME): A CNAME maps a hostname to another hostname, not to an IP address - you can't point a CNAME at an IP. Also, CNAMEs cannot be used at the zone apex (example.com itself).
• E (Auto Scaling group): Scaling out can spin up additional instances with different IPs, which breaks the single static IP requirement and adds unnecessary complexity.

Memory tip: Think of it as two layers - "lock the IP, then label it." EIP locks a static IP to your instance (D), and an A record ("A for Address") labels that IP with your domain name (B). If you see a question requiring a static IP on EC2 + DNS, reach for EIP + A record first.

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