The answer is the route tables in the VPC must have routes pointing to the virtual private gateway for the on-premises CIDR. Even when a VPN tunnel shows UP, traffic cannot flow if the VPC route table lacks a destination route for the on-premises network pointing to the virtual private gateway (VGW); without this route, the VPC simply does not know where to send return traffic. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding that a tunnel UP confirms IPSec Phase 1 and Phase 2 are healthy, but routing is a separate control plane issue—a common trap is assuming the tunnel status guarantees end-to-end connectivity. Remember, the VPN tunnel is the highway, but the route table is the exit sign; if the sign is missing, traffic never leaves the VPC. Memory tip: “Tunnel UP, route missing? Check the VPC route table for the VGW target.”
SOA-C02 Networking and Content Delivery Practice Question
This SOA-C02 practice question tests your understanding of networking and content delivery. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company has a VPN connection between its on-premises network and AWS VPC. The VPN tunnel shows status as UP, but traffic is not flowing from on-premises to the VPC. Which configuration should be checked?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The route tables in the VPC have routes pointing to the virtual private gateway for the on-premises CIDR.
Option B is correct because the route tables in the VPC must have routes pointing to the virtual private gateway for the on-premises network. Without them, traffic from the VPC to on-premises will not be routed. Option A is wrong because the tunnel state is UP, indicating Phase 1 and Phase 2 are fine. Option C is wrong because the customer gateway device must have correct routing, but the question is about VPC side. Option D is wrong because security groups control traffic to/from instances, but if routing is missing, traffic won't reach the VPN.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 IKE versions on the customer gateway and virtual private gateway match.
Why it's wrong here
If they didn't match, the tunnel would not be UP.
✓
The route tables in the VPC have routes pointing to the virtual private gateway for the on-premises CIDR.
Why this is correct
Without proper routes, the VPC does not know to send traffic for on-premises through the VPN.
The customer gateway device is configured to forward traffic to the VPC.
Why it's wrong here
This is important but the question is about VPC side; the tunnel is UP, so on-premises is likely configured correctly.
✗
The security groups allow inbound traffic from the on-premises network.
Why it's wrong here
Security groups are instance-level; traffic must first be routed to the instance, which requires proper routing.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Networking and Content Delivery — This question tests Networking and Content Delivery — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The route tables in the VPC have routes pointing to the virtual private gateway for the on-premises CIDR. — Option B is correct because the route tables in the VPC must have routes pointing to the virtual private gateway for the on-premises network. Without them, traffic from the VPC to on-premises will not be routed. Option A is wrong because the tunnel state is UP, indicating Phase 1 and Phase 2 are fine. Option C is wrong because the customer gateway device must have correct routing, but the question is about VPC side. Option D is wrong because security groups control traffic to/from instances, but if routing is missing, traffic won't reach the VPN.
What should I do if I get this SOA-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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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 has a VPC with an IPv4 CIDR block of 10.0.0.0/16. The company wants to connect two subnets: one in the VPC (10.0.1.0/24) and one in an on-premises network (192.168.1.0/24) via a Site-to-Site VPN. The VPN connection is established. However, instances in the VPC subnet cannot ping the on-premises server at 192.168.1.10. What is a possible cause?
medium
A.The VPN tunnel is not in the UP state
✓ B.The route table for the VPC subnet does not have a route to the on-premises network via the VPN gateway
C.The security group for the VPC instances does not allow ICMP traffic
D.The VPC does not have a VPC endpoint for the VPN service
Why B: Option B is correct because the VPC subnet's route table must have a route for the on-premises CIDR pointing to the VPN gateway. Option A is wrong because the VPN connection uses the internet, not a VPC endpoint. Option C is wrong because security groups control traffic to/from instances, but the route is missing. Option D is wrong because the VPN is established, so tunnel is up.
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This SOA-C02 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 SOA-C02 exam.
Question Discussion
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