- A
The private hosted zone is not associated with the VPC.
Correct. If the private hosted zone is not associated with the VPC, the VPC's DNS resolver will not have the zone's records, causing resolution failure even when queries are forwarded from on-premises.
- B
The VPC's DHCP option set is not configured to use the Route 53 Resolver.
Why wrong: Incorrect. The VPC's DHCP option set configures DNS servers for instances within the VPC, but it does not affect the VPC DNS resolver's ability to resolve private hosted zones. The resolver is always the same (the Route 53 Resolver) regardless of DHCP options.
- C
The security group for the VPC DNS resolver is blocking inbound UDP port 53 from the on-premises network.
Why wrong: Incorrect. The VPC DNS resolver (Route 53 Resolver) is a managed service and does not have a security group. Network ACLs could potentially block traffic, but they are not mentioned in the scenario, and this is not the most likely cause.
- D
A Route 53 Resolver outbound endpoint is not configured to forward queries from on-premises to the VPC.
Why wrong: Incorrect. An outbound endpoint forwards queries from the VPC to on-premises DNS servers, not the reverse. To accept inbound queries from on-premises, an inbound endpoint is required. However, even with an inbound endpoint, the private hosted zone must still be associated with the VPC.
Configuring Route 53 Resolver Inbound Endpoint for On-Premises DNS Resolution
This ANS-C01 practice question tests your understanding of network implementation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: private Hosted Zone Association. 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 uses AWS Direct Connect with a private VIF to connect to a VPC. They have an on-premises application that needs to resolve private hosted zone names in Amazon Route 53. The on-premises DNS server forwards queries for the private domain to the VPC's DNS resolver. However, resolution fails. What is the most likely cause?
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 private hosted zone is not associated with the VPC.
The most likely cause is that the private hosted zone is not associated with the VPC. For Route 53 private hosted zones, the zone must be explicitly associated with the VPC in which the DNS resolver operates. If the zone is not associated, the VPC's DNS resolver (Route 53 Resolver) will not respond to queries for that domain, even if queries are forwarded from on-premises. The on-premises DNS server forwards queries to the VPC's DNS resolver, but without zone association, the resolver has no knowledge of the private hosted zone. Options B and C are incorrect because DHCP option sets and security groups do not directly affect the VPC DNS resolver's ability to resolve private hosted zones. Option D is incorrect because an outbound endpoint is used to forward queries from the VPC to on-premises, not to accept inbound queries; the correct component would be an inbound endpoint, but the primary issue here is zone association.
Key principle: Private Hosted Zone Association
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 private hosted zone is not associated with the VPC.
Why this is correct
Correct. If the private hosted zone is not associated with the VPC, the VPC's DNS resolver will not have the zone's records, causing resolution failure even when queries are forwarded from on-premises.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Private Hosted Zone Association
- ✗
The VPC's DHCP option set is not configured to use the Route 53 Resolver.
- ✗
The security group for the VPC DNS resolver is blocking inbound UDP port 53 from the on-premises network.
Why it's wrong here
Incorrect. The VPC DNS resolver (Route 53 Resolver) is a managed service and does not have a security group. Network ACLs could potentially block traffic, but they are not mentioned in the scenario, and this is not the most likely cause.
- ✗
A Route 53 Resolver outbound endpoint is not configured to forward queries from on-premises to the VPC.
Why it's wrong here
Incorrect. An outbound endpoint forwards queries from the VPC to on-premises DNS servers, not the reverse. To accept inbound queries from on-premises, an inbound endpoint is required. However, even with an inbound endpoint, the private hosted zone must still be associated with the VPC.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap is that candidates often overlook the necessity of associating a private hosted zone with the VPC, and instead focus on DNS forwarding configurations like inbound/outbound endpoints. While an inbound endpoint is needed for on-premises resolution, the fundamental requirement is that the zone is associated with the VPC.
Trap categories for this question
Scenario analysis trap
Incorrect. The VPC DNS resolver (Route 53 Resolver) is a managed service and does not have a security group. Network ACLs could potentially block traffic, but they are not mentioned in the scenario, and this is not the most likely cause.
Detailed technical explanation
How to think about this question
Route 53 Resolver inbound endpoints are used to allow DNS queries from on-premises networks to be forwarded to the VPC's DNS resolver, while outbound endpoints forward queries from the VPC to on-premises DNS servers. In this scenario, the on-premises DNS server is forwarding queries to the VPC, so you need an inbound endpoint (often mislabeled as an outbound endpoint in the question) to receive those queries; the endpoint uses Elastic Network Interfaces (ENIs) in the VPC with specific IP addresses that the on-premises DNS server must target. Without this endpoint, the VPC's Route 53 Resolver will not listen for DNS queries from outside the VPC, even if the private hosted zone is associated.
KKey Concepts to Remember
- Private Hosted Zone Association
- Route 53 Resolver
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Private Hosted Zone Association
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.
Visual reference
Quick reference
Common DNS Record Types
| Record | Purpose | Example |
|---|---|---|
| A | IPv4 address mapping | example.com → 93.184.216.34 |
| AAAA | IPv6 address mapping | example.com → 2606:2800::1 |
| CNAME | Alias to another hostname | www → example.com |
| MX | Mail server for domain | example.com → mail.example.com (priority 10) |
| TXT | Text data (SPF, DKIM, verification) | v=spf1 include:_spf.example.com ~all |
| NS | Authoritative name servers | example.com NS ns1.example.com |
| PTR | Reverse DNS (IP → hostname) | 34.216.184.93.in-addr.arpa → example.com |
| SOA | Zone authority record | Primary NS, admin email, serial, TTL defaults |
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — Private Hosted Zone Association.
What is the correct answer to this question?
The correct answer is: The private hosted zone is not associated with the VPC. — The most likely cause is that the private hosted zone is not associated with the VPC. For Route 53 private hosted zones, the zone must be explicitly associated with the VPC in which the DNS resolver operates. If the zone is not associated, the VPC's DNS resolver (Route 53 Resolver) will not respond to queries for that domain, even if queries are forwarded from on-premises. The on-premises DNS server forwards queries to the VPC's DNS resolver, but without zone association, the resolver has no knowledge of the private hosted zone. Options B and C are incorrect because DHCP option sets and security groups do not directly affect the VPC DNS resolver's ability to resolve private hosted zones. Option D is incorrect because an outbound endpoint is used to forward queries from the VPC to on-premises, not to accept inbound queries; the correct component would be an inbound endpoint, but the primary issue here is zone association.
What should I do if I get this ANS-C01 question wrong?
Review private Hosted Zone Association, then practise related ANS-C01 questions on the same topic to reinforce the concept.
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?
Private Hosted Zone Association
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Last reviewed: Jul 4, 2026
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