ANS-C01 Network Implementation Practice Question
A company is configuring a site-to-site VPN connection between its on-premises network and AWS. The VPN tunnel is up, but traffic is not passing. The company has verified that routes are correct on both sides. Which TWO actions should the company take to troubleshoot the issue?
⚠ Common exam trap
The ANS-C01 exam often tests the distinction between security groups (stateful, instance-level) and network ACLs (stateless, subnet-level), and candidates may overlook that both must be correctly configured for traffic to pass, especially when the VPN tunnel itself is operational.
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
✓
Check the security group rules for the EC2 instances in the VPC.
Security groups act as a virtual firewall for EC2 instances, controlling inbound and outbound traffic at the instance level. Even if the VPN tunnel is up and routes are correct, the security group rules must allow the desired traffic (e.g., from the on-premises network CIDR) to reach the EC2 instances. Without proper inbound rules, traffic will be dropped at the instance level, preventing communication.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Verify that the virtual private gateway is attached to the VPC.
Why it's wrong here
If tunnel is up, VPG is attached.
- ✗
Ensure that the on-premises firewall is configured to allow IPSec traffic.
Why it's wrong here
Tunnel is up, so firewall allows IPSec.
- ✓
Check the security group rules for the EC2 instances in the VPC.
Why this is correct
Security groups can block traffic.
- ✗
Verify that the VPN tunnel is using the correct encryption algorithm.
Why it's wrong here
Tunnel is up, so encryption is fine.
- ✓
Check the network ACLs for the subnets.
Why this is correct
NACLs can block traffic even if routes are correct.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ANS-C01 exam.