ANS-C01 Network Implementation Practice Question
A network engineer is troubleshooting connectivity between an EC2 instance in a VPC and an on-premises server connected via AWS Site-to-Site VPN. The ping from the EC2 instance to the on-premises server fails. The VPN tunnel status shows 'UP'. Which configuration should the engineer check first?
⚠ Common exam trap
The ANS-C01 exam often tests the misconception that a UP VPN tunnel guarantees end-to-end connectivity, but the trap here is that routing within the VPC is a separate concern that must be explicitly configured.
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 route table associated with the EC2 instance's subnet for a route to the on-premises network
Even when the VPN tunnel is UP, traffic from the EC2 instance to the on-premises server will be dropped if the VPC route table associated with the instance's subnet does not contain a route pointing to the on-premises network via the virtual private gateway (VGW). The ping failure in this scenario is most likely due to missing routing, not tunnel misconfiguration, since the tunnel status is UP.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Ensure the customer gateway device is configured with the correct public IP address
Why it's wrong here
The customer gateway is on-premises; the tunnel being up indicates the public IP is correct.
- ✗
Check that the pre-shared key matches on both sides
Why it's wrong here
If the pre-shared key didn't match, the tunnel would not be up.
- ✓
Check the route table associated with the EC2 instance's subnet for a route to the on-premises network
Why this is correct
Without a route pointing traffic to the virtual private gateway, the VPN cannot forward packets.
- ✗
Verify that the VPN tunnel is using the correct encryption algorithms
Why it's wrong here
The tunnel is up, so encryption settings are correct.
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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.