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CV0-004 Practice Question: A cloud administrator manages a hybrid cloud…
A cloud administrator manages a hybrid cloud environment where on-premises servers connect to a VPC in AWS via a VPN connection. The on-premises network uses IP range 10.0.0.0/16. The VPC uses 172.16.0.0/16. The VPN is established and the tunnel status is UP. However, on-premises hosts cannot ping EC2 instances in the VPC. The administrator logs into an EC2 instance and can ping the on-premises VPN gateway IP. The security groups and network ACLs are configured to allow all traffic. The route tables in the VPC have a route to the on-premises network via the virtual private gateway. The on-premises firewall logs show that packets from the VPC are being dropped. What is the most likely cause?
⚠ Common exam trap
A common mix-up: candidates assume a UP VPN tunnel guarantees end-to-end connectivity, ignoring that on-premises firewalls often require explicit allow rules for the VPC CIDR, even when the tunnel is established.
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
✓
The on-premises firewall is blocking traffic from the VPC CIDR range.
The on-premises firewall logs explicitly show that packets from the VPC are being dropped, indicating the firewall is filtering traffic from the VPC CIDR range (172.16.0.0/16). Since the VPN tunnel is UP, the EC2 instance can ping the on-premises VPN gateway IP, and security groups/network ACLs allow all traffic, the only remaining point of failure is the on-premises firewall blocking the return 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.
- ✗
The VPN tunnel is misconfigured and not passing traffic.
Why it's wrong here
The tunnel is demonstrably passing traffic, since the EC2 instance successfully pings the on-premises VPN gateway IP, so misconfiguration is contradicted by the evidence. It tempts because a down tunnel is the usual cause of silent hybrid connectivity, but here the drop occurs at the on-premises firewall.
- ✓
The on-premises firewall is blocking traffic from the VPC CIDR range.
Why this is correct
The EC2 instance can reach the on-premises VPN gateway, proving the tunnel and VPC routing work. Since on-premises firewall logs show dropped packets from the VPC CIDR, the firewall is filtering that range, blocking return traffic to EC2 instances.
- ✗
The security group attached to the EC2 instance is blocking inbound ICMP.
Why it's wrong here
Security groups are stated to allow all traffic, and the on-premises firewall logs show packets arriving from the VPC before being dropped, so the block is not at the instance. It tempts because security groups commonly block ICMP, but the evidence places the failure on-premises.
- ✗
The VPC route table does not have a route to the on-premises network.
Why it's wrong here
The VPC route table already contains a route to the on-premises network via the virtual private gateway, and the EC2 instance reaches the on-premises gateway, proving return routing works. It tempts because missing routes are a frequent hybrid fault, but the drop is logged on-premises.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CV0-004 practice question is part of Courseiva's free CompTIA 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 CV0-004 exam.