The answer is to enable Transit Gateway Flow Logs and review CloudWatch metrics for VPN tunnels. These two actions directly address Transit Gateway high latency troubleshooting by providing the necessary data to isolate the problem: CloudWatch metrics reveal packet loss and latency on the Site-to-Site VPN component, while Transit Gateway Flow Logs capture IP traffic between attachments, allowing you to identify which VPC or VPN link is contributing to the delay. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of layered monitoring—you must know that VPN metrics expose the WAN link health, while flow logs reveal internal routing and drop patterns. A common trap is to jump straight to checking route tables or NAT gateways, but latency issues often stem from the VPN tunnel itself or asymmetric traffic flows between attachments. Memory tip: think “VPN for the pipe, Flow Logs for the packets” to remember which tool diagnoses the connection versus the conversation.
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 network engineer is troubleshooting high latency on an AWS Transit Gateway that connects multiple VPCs and an on-premises network via AWS Site-to-Site VPN. The engineer wants to identify potential causes. Which TWO actions should the engineer take? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Review the CloudWatch metrics for the VPN tunnels for packet loss and latency.
Option B is correct because CloudWatch metrics for VPN tunnels provide direct visibility into packet loss and latency, which are key indicators of performance issues on the AWS Site-to-Site VPN component of the Transit Gateway. Option C is correct because Transit Gateway Flow Logs capture IP traffic information between attachments, allowing the engineer to analyze traffic patterns, identify drops, and pinpoint which VPC or VPN attachment is contributing to the high latency.
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.
✗
Review the NACL rules for each subnet in the VPCs.
Why it's wrong here
NACLs affect allowed traffic but not latency.
✓
Review the CloudWatch metrics for the VPN tunnels for packet loss and latency.
Why this is correct
VPN tunnel metrics can indicate performance issues.
Related concept
Read the scenario before looking for a memorised answer.
✓
Enable Transit Gateway Flow Logs to capture traffic between attachments.
Why this is correct
Transit Gateway Flow Logs provide visibility into traffic flows.
Related concept
Read the scenario before looking for a memorised answer.
✗
Re-create the VPN connections to reset the tunnels.
Why it's wrong here
Re-creating is a disruptive action, not a diagnostic step.
✗
Enable VPC Flow Logs on the VPCs attached to the transit gateway.
Why it's wrong here
VPC Flow Logs do not capture transit gateway traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse VPC Flow Logs with Transit Gateway Flow Logs, assuming VPC Flow Logs can diagnose Transit Gateway latency, but VPC Flow Logs lack the attachment-level context and latency metrics needed for this specific troubleshooting scenario.
Detailed technical explanation
How to think about this question
Transit Gateway Flow Logs record packet-level information such as source/destination IP, ports, protocol, and timestamps, enabling engineers to compute round-trip time (RTT) between attachments by correlating request and response flows. CloudWatch metrics for VPN tunnels include `TunnelDataIn`, `TunnelDataOut`, and `TunnelState`, but for latency analysis, engineers should monitor `TunnelPacketLoss` and `TunnelLatency` (if enabled via custom metrics from the VPN appliance). In real-world scenarios, asymmetric routing or MTU mismatches across attachments can cause packet drops that manifest as high latency, and these logs/metrics help isolate the specific attachment or tunnel at fault.
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.
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.
Network Management and Operations — This question tests Network Management and Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Review the CloudWatch metrics for the VPN tunnels for packet loss and latency. — Option B is correct because CloudWatch metrics for VPN tunnels provide direct visibility into packet loss and latency, which are key indicators of performance issues on the AWS Site-to-Site VPN component of the Transit Gateway. Option C is correct because Transit Gateway Flow Logs capture IP traffic information between attachments, allowing the engineer to analyze traffic patterns, identify drops, and pinpoint which VPC or VPN attachment is contributing to the high latency.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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