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Question 907 of 1,705

Network Management and Operations →hardMultiple ChoiceObjective-mapped

ANS-C01 Network Management and Operations Practice Question

This ANS-C01 practice question tests your understanding of network management and operations. 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 company has a hybrid network architecture with an AWS VPC (10.0.0.0/16) connected to an on-premises data center via AWS Direct Connect with a private VIF. The on-premises network uses 10.1.0.0/16. The VPC has subnets in two Availability Zones, each with a private subnet (10.0.1.0/24 and 10.0.2.0/24) and a public subnet. The company recently deployed a new application in the VPC that uses an Application Load Balancer (ALB) in the public subnets. The ALB targets EC2 instances in the private subnets. Users on-premises report that they cannot access the application using the ALB's DNS name. The on-premises network team confirms that they can ping the ALB's private IP address from on-premises. The VPC route tables have routes for the on-premises network pointing to the virtual private gateway (VGW). The security groups and network ACLs are configured to allow traffic from on-premises. What is the most likely cause of the issue?

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 VPC route tables do not have a route to the on-premises network for the ALB's subnet.
Why wrong: The route tables include routes for 10.1.0.0/16 via VGW.
B
The security group on the ALB blocks inbound traffic from the on-premises CIDR.
Why wrong: Security groups are configured to allow traffic from on-premises.
C
The ALB is deployed in private subnets instead of public subnets.
Why wrong: The stem says ALB is in public subnets.
D
The on-premises DNS resolver does not resolve the ALB's DNS name to a private IP address, causing traffic to go over the internet.
ALB DNS name resolves to public IPs; for private connectivity, private hosted zone or Route 53 Resolver must be used.

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 resolver does not resolve the ALB's DNS name to a private IP address, causing traffic to go over the internet.

Option D is correct because the ALB's DNS name resolves to public IP addresses by default. On-premises traffic destined for public IPs would go over the internet, not Direct Connect, unless the on-premises DNS resolver is configured to return the ALB's private IP address. Since on-premises users can ping the private IP, the issue is DNS resolution. Option A is incorrect because route tables already have routes to on-premises. Option B is incorrect because the security group on the ALB is configured to allow traffic from on-premises. Option C is incorrect because the ALB is deployed in public subnets, not private subnets.

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.

✗
The VPC route tables do not have a route to the on-premises network for the ALB's subnet.
Why it's wrong here
The route tables include routes for 10.1.0.0/16 via VGW.
✗
The security group on the ALB blocks inbound traffic from the on-premises CIDR.
Why it's wrong here
Security groups are configured to allow traffic from on-premises.
✗
The ALB is deployed in private subnets instead of public subnets.
Why it's wrong here
The stem says ALB is in public subnets.
✓
The on-premises DNS resolver does not resolve the ALB's DNS name to a private IP address, causing traffic to go over the internet.
Why this is correct
ALB DNS name resolves to public IPs; for private connectivity, private hosted zone or Route 53 Resolver must be used.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.

Common exam traps

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.

Visual reference

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.

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FAQ

Questions learners often ask

What does this ANS-C01 question test?

Network Management and Operations — This question tests Network Management and Operations — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: The on-premises DNS resolver does not resolve the ALB's DNS name to a private IP address, causing traffic to go over the internet. — Option D is correct because the ALB's DNS name resolves to public IP addresses by default. On-premises traffic destined for public IPs would go over the internet, not Direct Connect, unless the on-premises DNS resolver is configured to return the ALB's private IP address. Since on-premises users can ping the private IP, the issue is DNS resolution. Option A is incorrect because route tables already have routes to on-premises. Option B is incorrect because the security group on the ALB is configured to allow traffic from on-premises. Option C is incorrect because the ALB is deployed in public subnets, not private subnets.

What should I do if I get this ANS-C01 question wrong?

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?

CIDR notation defines the prefix length.

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