The answer is to configure the ALB listener for HTTPS and the target group for HTTPS using a self-signed certificate on the EC2 instances. This works because the Application Load Balancer can terminate the client’s HTTPS connection at the listener, then re-encrypt traffic to the backend using the same protocol, ensuring end-to-end encryption in transit without requiring a public certificate for the instances. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of ALB target group encryption options and the distinction between terminating HTTPS at the load balancer versus preserving it to the backend. A common trap is assuming you need a managed CA like ACM Private CA for simplicity, but a self-signed certificate is sufficient for internal traffic between ALB and EC2 instances. Remember the mnemonic: “ALB to backend, self-signed is your friend.”
DOP-C02 Security and Compliance Practice Question
This DOP-C02 practice question tests your understanding of security and compliance. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A DevOps engineer needs to encrypt data in transit between an Application Load Balancer (ALB) and backend EC2 instances. The application uses HTTPS. What is the simplest way to achieve this encryption?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the ALB listener to use HTTPS, and configure the target group to use HTTPS with a self-signed certificate on the instances.
An ALB can terminate HTTPS at the listener and then communicate with backend instances using HTTP if desired. However, to encrypt in transit, you can use HTTPS between ALB and instances as well. The simplest way is to install the same certificate on both ALB and instances, but ALB can use a self-signed certificate. Using an internal CA or ACM Private CA is more complex. Using a TCP listener does not provide encryption.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use an AWS Private Certificate Authority to issue certificates for the instances.
Why it's wrong here
This is more complex than needed.
✗
Use a Network Load Balancer instead with TLS listeners.
Why it's wrong here
NLB is not simpler; ALB can do this.
✗
Place both ALB and instances in a VPC with default security groups.
Why it's wrong here
Default security groups do not encrypt traffic.
✓
Configure the ALB listener to use HTTPS, and configure the target group to use HTTPS with a self-signed certificate on the instances.
Why this is correct
This encrypts traffic between ALB and instances.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
Security and Compliance — This question tests Security and Compliance — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Configure the ALB listener to use HTTPS, and configure the target group to use HTTPS with a self-signed certificate on the instances. — An ALB can terminate HTTPS at the listener and then communicate with backend instances using HTTP if desired. However, to encrypt in transit, you can use HTTPS between ALB and instances as well. The simplest way is to install the same certificate on both ALB and instances, but ALB can use a self-signed certificate. Using an internal CA or ACM Private CA is more complex. Using a TCP listener does not provide encryption.
What should I do if I get this DOP-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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