The answer is to associate the private hosted zone with the authorized VPCs. This configuration works because Route 53 private hosted zones are inherently scoped to the VPCs with which they are associated; only those VPCs receive DNS responses for the zone’s records, effectively restricting access at the DNS query level. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this concept tests your understanding of how Route 53 authorization differs from network-layer controls—a common trap is confusing IAM policies (which govern API calls to modify the zone) with DNS query access, or applying security groups or NACLs that operate at the instance or subnet level and cannot filter DNS resolution. Remember the key distinction: VPC association controls who can *resolve*, while IAM controls who can *manage*. A useful memory tip is “Associate to authorize”—the association itself is the access control mechanism for DNS queries.
ANS-C01 Network Security, Compliance and Governance Practice Question
This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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 is using Amazon Route 53 for DNS resolution. They want to restrict access to a private hosted zone so that only authorized VPCs can query it. Which configuration should they use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Associate the private hosted zone with the authorized VPCs
Option A is correct because associating a private hosted zone with VPCs allows only those VPCs to resolve records. Option B (IAM policy) affects API calls, not DNS queries. Option C (security group) is for network interfaces. Option D (NACL) is subnet-level.
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.
✗
Configure a network ACL to block UDP port 53 from other VPCs
Why it's wrong here
NACLs are subnet-level, but DNS queries are resolved by Route 53, not by instances.
✗
Create an IAM policy to deny DNS queries from other VPCs
Why it's wrong here
IAM policies do not apply to DNS queries; they apply to API calls.
✗
Configure a security group to block DNS traffic from other VPCs
Why it's wrong here
Security groups apply to EC2 instances, not Route 53.
✓
Associate the private hosted zone with the authorized VPCs
Why this is correct
Private hosted zones are accessible only to associated VPCs.
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 ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Associate the private hosted zone with the authorized VPCs — Option A is correct because associating a private hosted zone with VPCs allows only those VPCs to resolve records. Option B (IAM policy) affects API calls, not DNS queries. Option C (security group) is for network interfaces. Option D (NACL) is subnet-level.
What should I do if I get this ANS-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 ANS-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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