ANS-C01 Network Management and Operations Practice Question
A network engineer is troubleshooting a VPN connection between an AWS Virtual Private Gateway and an on-premises Cisco ASA. The tunnel status shows 'UP' but no traffic passes. The engineer checks the route tables and finds the correct static routes on both sides. What should the engineer check next?
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
✓
Review the IPsec phase 2 settings, including the traffic selectors.
If the tunnel is up but no traffic passes, the issue is often phase 2 IPsec security associations (SAs) or mismatch in encryption domains. Unlike phase 1, phase 2 can fail silently.
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 IPsec phase 2 settings, including the traffic selectors.
Why this is correct
Phase 2 parameters or mismatched encryption domains could cause the tunnel to be UP but not pass traffic.
- ✗
Check the IKE phase 1 parameters (e.g., encryption, hash).
Why it's wrong here
Phase 1 mismatch would also prevent the tunnel from being UP.
- ✗
Verify that the pre-shared keys match.
Why it's wrong here
Mismatched PSK would prevent phase 1, so the tunnel would not be UP.
- ✗
Confirm that the VPC route table has a route to the on-premises subnet.
Why it's wrong here
The engineer already checked route tables and found static routes correct.
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
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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 network engineer is configuring a Site-to-Site VPN connection between an on-premises network and AWS. The VPN tunnel status shows 'UP' but traffic is not passing. The engineer checks the route tables and finds that the VPC route table has a route pointing to the virtual private gateway for the on-premises CIDR. What is the most likely missing configuration?
medium- A.The VPC route table does not have a route for the on-premises CIDR pointing to the virtual private gateway
- ✓ B.The security group of the EC2 instances does not allow inbound traffic from on-premises
- C.The VPN tunnel is using the wrong pre-shared key
- D.The on-premises router is not advertising the VPC CIDR over BGP
Why B: Since the VPN tunnel status is 'UP', the pre-shared key and Phase 2 parameters are correctly configured. With the VPC route table already pointing to the virtual private gateway for the on-premises CIDR, the most likely missing configuration is that the security group associated with the EC2 instances in the VPC does not allow inbound traffic from the on-premises network. Security groups act as a virtual firewall for instances, and inbound traffic from on-premises must be explicitly allowed. Option A is incorrect because the stem states the route exists. Option C is incorrect because a tunnel UP status confirms the pre-shared keys match. Option D is less likely because even if the on-premises router is not advertising the VPC CIDR, that would affect return traffic but not necessarily all traffic; also the question does not specify BGP usage.
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.