Jeff’s Note #
Unlike generic exam dumps, ADH analyzes this scenario through the lens of a Real-World Lead Developer.
For DVA-C02 candidates, the confusion often lies in distinguishing which AWS services provide real-time diagnostic network information versus policy auditing or security analysis. In production, this is about knowing exactly which AWS tool gives you visibility into packet-level traffic flow and connectivity paths between your application layers. Let’s drill down.
The Certification Drill (Simulated Question) #
Scenario #
Silverline Analytics has deployed a multi-tier financial analytics platform on Amazon EC2 instances. The architecture consists of web front-end servers, application servers, and a backend database. Recently, the engineering team observed intermittent failures in requests from the application servers to the database servers. There is suspicion of network connectivity issues, but the root cause is unknown.
The Requirement: #
Identify the AWS services or tools that will help the development team pinpoint the faulty component causing connectivity problems between the application layer and the database servers.
The Options #
- A) Use AWS CloudTrail to track API calls involved in network setup
- B) Use AWS Trusted Advisor to check for security or performance issues
- C) Enable Amazon VPC Flow Logs to capture IP traffic flow information
- D) Review and audit network access control lists (NACLs) configurations
- E) Use AWS Config rules to audit configuration compliance of networking components
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Correct Answer #
C and D.
Quick Insight: The Developer Imperative #
Real-time network troubleshooting requires visibility into IP traffic flows and packet acceptance/rejections at subnet boundary controls (NACLs). VPC Flow Logs give you granular, continuous data of traffic engaged in sending or dropping packets. NACLs audits help confirm if network boundary rules are blocking or allowing traffic. CloudTrail, Trusted Advisor, and AWS Config primarily help with auditing API calls, high-level checks, or compliance, but not direct connectivity diagnostics.
Content Locked: The Expert Analysis #
You’ve identified the answer. But do you know the implementation details that separate a Junior from a Senior?
The Expert’s Analysis #
Correct Answer #
Options C and D
The Winning Logic #
- Amazon VPC Flow Logs capture detailed information about the IP traffic going to and from network interfaces in your VPC, including allowed and denied traffic, which is instrumental for tracing connectivity between EC2 tiers and databases.
- Network Access Control Lists (NACLs) act as stateless firewalls at the subnet level. Reviewing NACL rules provides insight into whether traffic is permitted or denied at the subnet boundaries, helping isolate if network policy is blocking connectivity.
The Trap (Distractor Analysis): #
- Why not A (CloudTrail)? CloudTrail logs AWS API calls for auditing and compliance but does not provide packet-level network traffic data or connectivity status between components.
- Why not B (Trusted Advisor)? Trusted Advisor focuses on best practices, cost optimization, and security checks but does not deliver live network traffic diagnostics.
- Why not E (AWS Config rules)? Config captures resource configuration drift or compliance but lacks the granularity to show actual traffic flow or real-time connectivity problems.
The Technical Blueprint #
Relevant CLI commands to enable VPC Flow Logs and review NACLs: #
# Enable VPC Flow Logs on a subnet or network interface
aws ec2 create-flow-logs --resource-type Subnet --resource-ids subnet-12345678 \
--traffic-type ALL --log-group-name VPCFlowLogs --deliver-logs-permission-arn arn:aws:iam::123456789012:role/FlowLogsRole
# Describe network ACL entries attached to the subnet
aws ec2 describe-network-acls --filters Name=association.subnet-id,Values=subnet-12345678
The Comparative Analysis #
| Option | Operational Overhead | Automation Level | Impact on Troubleshooting |
|---|---|---|---|
| A) CloudTrail | Low | High | Low - No packet flow info |
| B) Trusted Advisor | None | None | Low - Advisory only |
| C) VPC Flow Logs | Medium (logging cost) | Easy | High - Packet traffic insights |
| D) Network ACLs | Low | Manual | Medium - Policy analysis |
| E) AWS Config Rules | Medium | Automated | Low - Config compliance checks |
Real-World Application (Practitioner Insight) #
Exam Rule #
For the exam, always pick VPC Flow Logs (C) when you need detailed network traffic data and NACL review (D) for firewall rule analysis.
Real World #
In production, you might combine VPC Flow Logs with tools like Amazon CloudWatch Logs Insights for real-time log querying, or third-party network monitoring solutions for enhanced visualization and alerting.
(CTA) Stop Guessing, Start Mastering #
Disclaimer
This is a study note based on simulated scenarios for the DVA-C02 exam.