The answer is to enable VPC Flow Logs on the subnets of the VPCs, because this is the only option that provides packet-level metadata needed to diagnose intermittent drops. VPC Flow Logs capture information about accepted and rejected traffic, including source and destination IPs, ports, protocols, and the action taken by the security group or network ACL, allowing you to pinpoint exactly where packets are being dropped. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your ability to select the correct diagnostic tool for inter-VPC connectivity issues through a Transit Gateway, often as a distractor against CloudWatch metrics (which lack packet-level detail) or Transit Gateway Network Manager (which shows topology, not drops). A common trap is assuming CloudWatch metrics or Network Manager can reveal dropped packets, but they cannot. Remember the mnemonic: “Flow for Flaws” – when traffic fails, enable Flow Logs first.
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 deployed a multi-VPC architecture with AWS Transit Gateway. The network team notices that traffic between two VPCs is intermittently dropped. Both VPCs are attached to the same transit gateway. Which action should the network engineer take to troubleshoot the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable VPC Flow Logs on the subnets of the VPCs.
Option B is correct because enabling VPC Flow Logs captures IP traffic information, which helps identify dropped packets. Option A is wrong because CloudWatch metrics do not provide packet-level details. Option C is wrong because Transit Gateway Network Manager provides topology visualization, not packet drops. Option D is wrong because Direct Connect is unrelated to inter-VPC 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.
✗
Configure AWS Direct Connect to route traffic between the VPCs.
Why it's wrong here
Direct Connect is for on-premises connectivity, not inter-VPC traffic.
✗
Use Transit Gateway Network Manager to view the network topology.
Why it's wrong here
Network Manager shows topology, not packet drops.
✗
Enable CloudWatch metrics for the transit gateway attachments.
Why it's wrong here
CloudWatch metrics provide aggregated statistics, not packet-level drops.
✓
Enable VPC Flow Logs on the subnets of the VPCs.
Why this is correct
VPC Flow Logs capture detailed traffic data, including dropped packets.
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.
Trap categories for this question
Command / output trap
Network Manager shows topology, not packet drops.
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.
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.
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: Enable VPC Flow Logs on the subnets of the VPCs. — Option B is correct because enabling VPC Flow Logs captures IP traffic information, which helps identify dropped packets. Option A is wrong because CloudWatch metrics do not provide packet-level details. Option C is wrong because Transit Gateway Network Manager provides topology visualization, not packet drops. Option D is wrong because Direct Connect is unrelated to inter-VPC traffic.
What should I do if I get this ANS-C01 question wrong?
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.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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