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Networking and Content Delivery →mediumMultiple ChoiceObjective-mapped

SOA-C02 Networking and Content Delivery Practice Question

This SOA-C02 practice question tests your understanding of networking and content delivery. 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 SysOps administrator is troubleshooting connectivity issues between two VPCs that are peered using a VPC Peering connection. The instances in VPC A can ping the private IP of instances in VPC B, but not the DNS names. 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.

A
The route tables in VPC A do not have a route to VPC B's CIDR.
Why wrong: Ping works, so routing is correct.
B
The security groups in VPC B block DNS traffic (port 53).
Why wrong: DNS resolution is a VPC feature, not instance-level.
C
The VPC Peering connection does not have 'Enable DNS Resolution' enabled.
DNS resolution across VPC peering requires this option.
D
The VPCs have overlapping CIDR blocks.
Why wrong: Overlapping CIDR would prevent peering setup.

Full breakdown with real-world context →

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 VPC Peering connection does not have 'Enable DNS Resolution' enabled.

Option C is correct because the 'Enable DNS Resolution' setting on a VPC Peering connection allows instances in one VPC to resolve the private DNS hostnames of instances in the peered VPC. Without this setting enabled, the DNS resolver in the requester VPC will not return the private IP of the peered instance, causing DNS name resolution to fail even though direct ICMP (ping) to the private IP works. This setting must be enabled on both sides of the peering connection for cross-VPC DNS resolution to function.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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 route tables in VPC A do not have a route to VPC B's CIDR.
Why it's wrong here
Ping works, so routing is correct.
✗
The security groups in VPC B block DNS traffic (port 53).
Why it's wrong here
DNS resolution is a VPC feature, not instance-level.
✓
The VPC Peering connection does not have 'Enable DNS Resolution' enabled.
Why this is correct
DNS resolution across VPC peering requires this option.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The VPCs have overlapping CIDR blocks.
Why it's wrong here
Overlapping CIDR would prevent peering setup.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often confuse successful ICMP connectivity with full network functionality, overlooking that DNS resolution is a separate service that requires explicit configuration on the VPC peering connection.

Detailed technical explanation

How to think about this question

The 'Enable DNS Resolution' setting modifies the behavior of the Amazon Route 53 Resolver within the VPC. When enabled, the VPC's DNS server (at the .2 address) will return the private IP of an instance in the peered VPC when queried for its private DNS hostname. Without this setting, the DNS server only resolves hostnames within its own VPC. This is distinct from 'Enable DNS Hostnames', which controls whether instances receive a public DNS name, and both settings must be enabled for full cross-VPC DNS functionality.

KKey Concepts to Remember

Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.

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

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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.

Visual reference

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this SOA-C02 question test?

Networking and Content Delivery — This question tests Networking and Content Delivery — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The VPC Peering connection does not have 'Enable DNS Resolution' enabled. — Option C is correct because the 'Enable DNS Resolution' setting on a VPC Peering connection allows instances in one VPC to resolve the private DNS hostnames of instances in the peered VPC. Without this setting enabled, the DNS resolver in the requester VPC will not return the private IP of the peered instance, causing DNS name resolution to fail even though direct ICMP (ping) to the private IP works. This setting must be enabled on both sides of the peering connection for cross-VPC DNS resolution to function.

What should I do if I get this SOA-C02 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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?

Read the scenario before looking for a memorised answer.

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This SOA-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 SOA-C02 exam.