The correct answer is three security group rules: an inbound HTTPS rule from 0.0.0.0/0 on the ALB security group, an inbound HTTP rule from 0.0.0.0/0 on the ALB security group, and an inbound HTTP rule on the EC2 security group that references the ALB security group as the source. This configuration ensures the Application Load Balancer terminates SSL/TLS, so only HTTP traffic flows between the ALB and EC2 instances, reducing the backend’s encryption overhead and keeping the instances isolated from direct internet access. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of least-privilege network segmentation and the ALB’s role as a reverse proxy—a common trap is adding an HTTPS rule on the EC2 side or allowing traffic from 0.0.0.0/0 directly to the instances, which bypasses the load balancer’s security controls. Remember the memory tip: “ALB handles the HTTPS handshake; EC2 only needs HTTP from the ALB.”
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 company runs a web application on EC2 instances behind an Application Load Balancer (ALB). The security team wants to allow only HTTP and HTTPS traffic from the internet to the ALB, and only HTTP traffic from the ALB to the EC2 instances. Which THREE security group configurations are required? (Choose three.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ALB security group: inbound rule allowing HTTP from 0.0.0.0/0.
Options A, C, and D are correct. Option A is correct for allowing HTTPS to ALB. Option C is correct for allowing HTTP to ALB. Option D is correct for allowing HTTP from ALB to EC2. Option B is wrong because HTTPS should not be terminated on EC2 if ALB handles SSL. Option E is wrong because it restricts from internet directly to EC2, bypassing ALB.
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.
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ALB security group: inbound rule allowing HTTP from 0.0.0.0/0.
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 SCS-C02 NAT questions on configuration and troubleshooting.
Infrastructure Security — This question tests Infrastructure Security — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: ALB security group: inbound rule allowing HTTP from 0.0.0.0/0. — Options A, C, and D are correct. Option A is correct for allowing HTTPS to ALB. Option C is correct for allowing HTTP to ALB. Option D is correct for allowing HTTP from ALB to EC2. Option B is wrong because HTTPS should not be terminated on EC2 if ALB handles SSL. Option E is wrong because it restricts from internet directly to EC2, bypassing ALB.
What should I do if I get this SCS-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 SCS-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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