The answer is to check the network ACL (NACL) associated with the Redshift cluster's subnet. This is correct because Amazon Redshift operates within a VPC, and while security groups act as a stateful firewall at the instance level, network ACLs provide a stateless layer of traffic control at the subnet boundary. Even if the security group permits inbound traffic from a specific IP range, the NACL can independently deny that traffic if its inbound or outbound rules are misconfigured. On the AWS Certified Data Engineer Associate DEA-C01 exam, this question tests your understanding of the layered security model in a VPC, a common trap where candidates focus only on security groups and forget the subnet-level filter. Remember, security groups are stateful and allow return traffic automatically, but NACLs are stateless and require explicit rules for both inbound and outbound traffic. A helpful memory tip: "SGs guard the instance, NACLs guard the subnet."
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and governance. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 data engineer is troubleshooting an Amazon Redshift cluster that is not allowing connections from a specific IP range. The engineer verified that the cluster's security group allows inbound traffic from the IP range. What is the next step to resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check the network ACL (NACL) associated with the Redshift cluster's subnet.
Option C is correct because Redshift also uses a VPC network ACL (NACL) that can block traffic at the subnet level, independent of security groups. Option A is wrong because the security group already allows traffic. Option B is wrong because IAM roles do not control network-level access. Option D is wrong because the cluster parameter group does not control network access.
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.
✗
Modify the Redshift cluster parameter group to enable public accessibility.
Why it's wrong here
Public accessibility is a cluster setting, but parameter groups do not control network access.
✗
Verify that the cluster's security group is attached to the Redshift cluster.
Why it's wrong here
The security group is already verified to allow traffic.
✗
Check the IAM role associated with the Redshift cluster.
Why it's wrong here
IAM roles manage permissions, not network access.
✓
Check the network ACL (NACL) associated with the Redshift cluster's subnet.
Why this is correct
NACLs can block traffic at the subnet level even if security groups allow it.
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 DEA-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Data Security and Governance — This question tests Data Security and Governance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Check the network ACL (NACL) associated with the Redshift cluster's subnet. — Option C is correct because Redshift also uses a VPC network ACL (NACL) that can block traffic at the subnet level, independent of security groups. Option A is wrong because the security group already allows traffic. Option B is wrong because IAM roles do not control network-level access. Option D is wrong because the cluster parameter group does not control network access.
What should I do if I get this DEA-C01 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 DEA-C01 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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