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Question 484 of 1,705

Network Management and Operations →mediumMultiple SelectObjective-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 VPC with public and private subnets. The private subnets have a route to a NAT gateway. The network team wants to monitor DNS queries from EC2 instances in private subnets to a custom DNS resolver on-premises over a VPN. Which TWO services can capture this traffic?

A
Amazon Route 53 Resolver query logs
Why wrong: Resolver query logs capture queries to Route 53, not custom on-premises resolvers.
B
Amazon CloudWatch
Why wrong: CloudWatch is for monitoring metrics and logs, not capturing traffic directly.
C
VPC Flow Logs
Flow logs capture all IP traffic, including DNS queries.
D
AWS Network Firewall
Network Firewall can log traffic including DNS based on stateful rules.
E
AWS CloudTrail
Why wrong: CloudTrail records API calls, not network traffic.

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

✓

VPC Flow Logs

VPC Flow Logs capture IP traffic at the network interface level, including DNS queries (port 53) to any destination, such as a custom on-premises resolver over VPN. AWS Network Firewall can inspect and log DNS traffic that passes through it, including queries to custom resolvers. Option A (Route 53 Resolver query logs) is incorrect because it only logs queries made to Amazon Route 53 Resolver, not to custom on-premises resolvers. Option B (CloudWatch) is incorrect because CloudWatch does not directly capture network traffic; it can aggregate logs but cannot capture raw DNS packets. Option E (CloudTrail) is incorrect because it logs API calls to AWS services, not network traffic.

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.

✗
Amazon Route 53 Resolver query logs
Why it's wrong here
Resolver query logs capture queries to Route 53, not custom on-premises resolvers.
✗
Amazon CloudWatch
Why it's wrong here
CloudWatch is for monitoring metrics and logs, not capturing traffic directly.
✓
VPC Flow Logs
Why this is correct
Flow logs capture all IP traffic, including DNS queries.
Related concept
CIDR notation defines the prefix length.
✓
AWS Network Firewall
Why this is correct
Network Firewall can log traffic including DNS based on stateful rules.
Related concept
CIDR notation defines the prefix length.
✗
AWS CloudTrail
Why it's wrong here
CloudTrail records API calls, not network traffic.

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 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.

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: VPC Flow Logs — VPC Flow Logs capture IP traffic at the network interface level, including DNS queries (port 53) to any destination, such as a custom on-premises resolver over VPN. AWS Network Firewall can inspect and log DNS traffic that passes through it, including queries to custom resolvers. Option A (Route 53 Resolver query logs) is incorrect because it only logs queries made to Amazon Route 53 Resolver, not to custom on-premises resolvers. Option B (CloudWatch) is incorrect because CloudWatch does not directly capture network traffic; it can aggregate logs but cannot capture raw DNS packets. Option E (CloudTrail) is incorrect because it logs API calls to AWS services, not network traffic.

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

What is the key concept behind this question?

CIDR notation defines the prefix length.

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