ANS-C01 Network Implementation Practice Question
A company is setting up a Site-to-Site VPN connection between an on-premises network and AWS. The VPN tunnel is established, but traffic is not flowing. Which THREE configuration items should be checked?
⚠ Common exam trap
Many candidates assume a 'UP' tunnel status guarantees traffic flow, but AWS explicitly tests that routing, security groups, and network ACLs are separate layers that must all be correctly configured for end-to-end connectivity.
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
✓
Route tables in the VPC and on-premises router.
Route tables in both the VPC and the on-premises router must have entries directing traffic for the remote network (e.g., the on-premises CIDR in the VPC route table, and the VPC CIDR in the on-premises route table) toward the VPN gateway or the VPN tunnel interface. Without these routes, packets have no path to reach the other side, even if the tunnel itself is up. This is a fundamental requirement for any Site-to-Site VPN to forward traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Route tables in the VPC and on-premises router.
Why this is correct
Routes are required for traffic forwarding.
- ✓
Security group rules for the EC2 instances.
Why this is correct
Security groups control inbound/outbound traffic.
- ✗
NAT gateway configuration in the VPC.
Why it's wrong here
NAT gateway is for internet access, not VPN.
- ✓
Network ACL rules for the subnets.
Why this is correct
NACLs are stateless and must allow traffic.
- ✗
Internet gateway attachment to the VPC.
Why it's wrong here
IGW is for internet access, not VPN.
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Same concept, more angles
1 more way this is tested on ANS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. 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?
hard- A.Verify that the virtual private gateway is attached to the VPC.
- B.Ensure that the on-premises firewall is configured to allow IPSec traffic.
- ✓ C.Check the security group rules for the EC2 instances in the VPC.
- D.Verify that the VPN tunnel is using the correct encryption algorithm.
- ✓ E.Check the network ACLs for the subnets.
Why C: 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.
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.