- A
The BU account's route table does not have a route to the NAT gateway's private IP. Add a route via the VPC peering connection.
Why wrong: The route is likely correct as mentioned in the stem.
- B
The security group attached to the NAT gateway's ENI does not allow incoming traffic from the BU private subnet. Update the security group to allow inbound traffic from the BU subnet CIDR.
NAT gateway's security group must allow inbound traffic from private subnets.
- C
The VPC peering connection is not in the 'active' state. Recreate the VPC peering connection.
Why wrong: The stem says route tables are correctly configured, implying the peering is active.
- D
The NAT gateway's Elastic IP is not attached. Attach an Elastic IP to the NAT gateway.
Why wrong: NAT gateway requires an EIP, but the issue is likely security group.
Quick Answer
The answer is to update the security group attached to the NAT gateway’s elastic network interface to allow inbound traffic from the BU private subnet CIDR. This is correct because VPC peering does not support transitive routing, meaning traffic from a BU’s private subnet must be explicitly permitted by the security group on the NAT gateway’s ENI in the shared services account; route tables alone cannot override security group rules. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of how security groups interact with VPC peering and NAT gateways—a common trap is assuming that correctly configured routes guarantee traffic flow, but security groups are stateful and must explicitly allow inbound traffic from the peered VPC CIDR. Remember the mnemonic: “Peering is not transitive, and security groups are not transitive either—inspect the ENI’s inbound rules first.”
SAP-C02 Practice Question: Design Solutions for Organizational Complexity
This SAP-C02 practice question tests your understanding of design solutions for organizational complexity. 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 large enterprise with multiple business units (BUs) uses AWS Organizations with a shared services account and BU-specific accounts. Each BU account has a VPC with multiple subnets. The shared services account hosts a central NAT gateway that provides outbound internet access to all BU private subnets via VPC peering. Recently, the network team noticed that traffic from one BU's private subnet is being blocked by the security group in the shared services account. They verified that the route tables are correctly configured. What is the most likely cause and solution?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The security group attached to the NAT gateway's ENI does not allow incoming traffic from the BU private subnet. Update the security group to allow inbound traffic from the BU subnet CIDR.
VPC peering does not support transitive routing. In this setup, traffic from BU private subnets goes to the NAT gateway in the shared services account via VPC peering. However, the NAT gateway's security group must allow inbound traffic from the BU private subnet CIDR. If it does not, traffic will be blocked. The solution is to update the NAT gateway's security group. Option D is correct.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The BU account's route table does not have a route to the NAT gateway's private IP. Add a route via the VPC peering connection.
Why it's wrong here
The route is likely correct as mentioned in the stem.
- ✓
The security group attached to the NAT gateway's ENI does not allow incoming traffic from the BU private subnet. Update the security group to allow inbound traffic from the BU subnet CIDR.
- ✗
The VPC peering connection is not in the 'active' state. Recreate the VPC peering connection.
Why it's wrong here
The stem says route tables are correctly configured, implying the peering is active.
- ✗
The NAT gateway's Elastic IP is not attached. Attach an Elastic IP to the NAT gateway.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SAP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
- →
Design Solutions for Organizational Complexity — study guide chapter
Learn the concepts, then practise the questions
- →
Design Solutions for Organizational Complexity practice questions
Targeted practice on this topic area only
- →
All SAP-C02 questions
1,746 questions across all exam domains
- →
AWS Certified Solutions Architect Professional SAP-C02 study guide
Full concept coverage aligned to exam objectives
- →
SAP-C02 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related SAP-C02 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Design Solutions for Organizational Complexity practice questions
Practise SAP-C02 questions linked to Design Solutions for Organizational Complexity.
Design for New Solutions practice questions
Practise SAP-C02 questions linked to Design for New Solutions.
Continuous Improvement for Existing Solutions practice questions
Practise SAP-C02 questions linked to Continuous Improvement for Existing Solutions.
Accelerate Workload Migration and Modernization practice questions
Practise SAP-C02 questions linked to Accelerate Workload Migration and Modernization.
SAA-C03 VPC practice questions
Practise SAP-C02 questions linked to SAA-C03 VPC.
SAA-C03 S3 lifecycle policy questions
Practise SAP-C02 questions linked to SAA-C03 S3 lifecycle policy questions.
SAA-C03 RDS Multi-AZ questions
Practise SAP-C02 questions linked to SAA-C03 RDS Multi-AZ questions.
SAA-C03 IAM policy practice questions
Practise SAP-C02 questions linked to SAA-C03 IAM policy.
SAA-C03 Route 53 failover questions
Practise SAP-C02 questions linked to SAA-C03 Route 53 failover questions.
SAA-C03 CloudFront practice questions
Practise SAP-C02 questions linked to SAA-C03 CloudFront.
SAA-C03 NAT gateway questions
Practise SAP-C02 questions linked to SAA-C03 NAT gateway questions.
SAA-C03 VPC endpoint questions
Practise SAP-C02 questions linked to SAA-C03 VPC endpoint questions.
Practice this exam
Start a free SAP-C02 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this SAP-C02 question test?
Design Solutions for Organizational Complexity — This question tests Design Solutions for Organizational Complexity — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The security group attached to the NAT gateway's ENI does not allow incoming traffic from the BU private subnet. Update the security group to allow inbound traffic from the BU subnet CIDR. — VPC peering does not support transitive routing. In this setup, traffic from BU private subnets goes to the NAT gateway in the shared services account via VPC peering. However, the NAT gateway's security group must allow inbound traffic from the BU private subnet CIDR. If it does not, traffic will be blocked. The solution is to update the NAT gateway's security group. Option D is correct.
What should I do if I get this SAP-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SAP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 20, 2026
This SAP-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAP-C02 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.