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Network Implementation →hardMultiple ChoiceObjective-mapped

ANS-C01 Network Implementation Practice Question

This ANS-C01 practice question tests your understanding of network implementation. 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 has a Direct Connect connection with a private VIF to a VPC. The on-premises network team notices that traffic to a particular EC2 instance is taking a suboptimal path that goes through the internet instead of Direct Connect. The EC2 instance has both a private IP and a public IP. The on-premises router is advertising the VPC's CIDR block over BGP. 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 private VIF is not configured to route the VPC CIDR.
Why wrong: The private VIF can route the VPC CIDR if advertised; the issue is that the on-premises device is using the public IP.
B
The security group on the EC2 instance is blocking traffic from the on-premises IP range.
Why wrong: Security groups control traffic at the instance level, but do not affect which path traffic takes.
C
The on-premises router is not advertising the VPC CIDR to the Direct Connect router.
Why wrong: The scenario states the on-premises router is advertising the VPC CIDR, so this is not the issue.
D
The on-premises DNS is resolving the EC2 instance's public IP address instead of its private IP address.
When using Direct Connect, you should use private IP addresses to ensure traffic stays on the private network.

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 on-premises DNS is resolving the EC2 instance's public IP address instead of its private IP address.

Option D is correct because the on-premises DNS is resolving the EC2 instance's public IP address instead of its private IP address. When the on-premises router advertises the VPC CIDR over BGP, traffic destined for the VPC should use Direct Connect. However, if DNS returns the public IP, the on-premises hosts will send traffic to the internet (via the public IP) rather than through the private VIF, causing a suboptimal path. This is a common misconfiguration where DNS resolution does not account for private connectivity.

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 private VIF is not configured to route the VPC CIDR.
Why it's wrong here
The private VIF can route the VPC CIDR if advertised; the issue is that the on-premises device is using the public IP.
✗
The security group on the EC2 instance is blocking traffic from the on-premises IP range.
Why it's wrong here
Security groups control traffic at the instance level, but do not affect which path traffic takes.
✗
The on-premises router is not advertising the VPC CIDR to the Direct Connect router.
Why it's wrong here
The scenario states the on-premises router is advertising the VPC CIDR, so this is not the issue.
✓
The on-premises DNS is resolving the EC2 instance's public IP address instead of its private IP address.
Why this is correct
When using Direct Connect, you should use private IP addresses to ensure traffic stays on the private network.
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.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often focus on BGP routing issues (like option C) or security group misconfigurations (option B), but the real cause is a DNS resolution problem that diverts traffic to the public IP, bypassing the Direct Connect path entirely.

Trap categories for this question

Scenario analysis trap
The scenario states the on-premises router is advertising the VPC CIDR, so this is not the issue.

Detailed technical explanation

How to think about this question

Under the hood, Direct Connect uses BGP to exchange routes between the on-premises router and the AWS side. When the on-premises router advertises the VPC CIDR, AWS installs a more specific route in the VPC route table for the Direct Connect virtual interface. However, DNS resolution is independent of routing; if the on-premises DNS server returns the public IP (e.g., via a public hosted zone or split-horizon DNS misconfiguration), the source host will use the public IP, which is routed over the internet. In real-world scenarios, this often occurs when using Route 53 private hosted zones incorrectly or when on-premises DNS is not configured to resolve private IPs for VPC resources.

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 ANS-C01 question test?

Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The on-premises DNS is resolving the EC2 instance's public IP address instead of its private IP address. — Option D is correct because the on-premises DNS is resolving the EC2 instance's public IP address instead of its private IP address. When the on-premises router advertises the VPC CIDR over BGP, traffic destined for the VPC should use Direct Connect. However, if DNS returns the public IP, the on-premises hosts will send traffic to the internet (via the public IP) rather than through the private VIF, causing a suboptimal path. This is a common misconfiguration where DNS resolution does not account for private connectivity.

What should I do if I get this ANS-C01 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 ANS-C01 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 ANS-C01 exam.