This ANS-C01 practice question tests your understanding of network implementation. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Network Topology
Refer to the exhibit. A VPN connection is established between an on-premises network (10.0.0.0/16) and an AWS VPC (172.16.0.0/16). The on-premises network can ping the VPC's private IP addresses, but the VPC cannot ping the on-premises network's IP addresses. The VPC route table has a route to 10.0.0.0/16 pointing to the VGW. What is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Network Topology
A
The VPN tunnels are not both in UP state
Why wrong: The exhibit shows state 'available'.
B
The VPN acceleration is disabled, causing high latency
Why wrong: Latency would not prevent pings.
C
The VPN connection is configured with static routes only and BGP is not used
Why wrong: Static routes are fine for this scenario.
D
The on-premises network does not have a route to the VPC CIDR (172.16.0.0/16) pointing to the customer gateway
Without a return route, traffic from VPC reaches on-premises but replies are dropped.
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 network does not have a route to the VPC CIDR (172.16.0.0/16) pointing to the customer gateway
The on-premises network can ping the VPC because the VPC route table has a route to 10.0.0.0/16 pointing to the virtual private gateway (VGW), so return traffic from the VPC is correctly forwarded. However, the VPC cannot ping the on-premises network because the on-premises router lacks a route back to the VPC CIDR (172.16.0.0/16) pointing to the customer gateway (CGW). Without this return route, traffic from the VPC reaches the on-premises network, but the on-premises router drops the response packets as it does not know how to reach 172.16.0.0/16.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 tunnels are not both in UP state
Why it's wrong here
The exhibit shows state 'available'.
✗
The VPN acceleration is disabled, causing high latency
Why it's wrong here
Latency would not prevent pings.
✗
The VPN connection is configured with static routes only and BGP is not used
Why it's wrong here
Static routes are fine for this scenario.
✓
The on-premises network does not have a route to the VPC CIDR (172.16.0.0/16) pointing to the customer gateway
Why this is correct
Without a return route, traffic from VPC reaches on-premises but replies are dropped.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The ANS-C01 exam often tests the concept that a VPN tunnel being 'UP' does not guarantee bidirectional traffic; candidates mistakenly assume tunnel status implies full connectivity, but the real issue is often a missing return route on the on-premises side.
Trap categories for this question
Command / output trap
The exhibit shows state 'available'.
Scenario analysis trap
Static routes are fine for this scenario.
Detailed technical explanation
How to think about this question
For a Site-to-Site VPN to support bidirectional communication, both the VPC route table and the on-premises routing table must have routes pointing to the respective next hops (VGW and CGW). The VPC route table automatically propagates routes from the VGW, but the on-premises router must be manually configured with a static route or BGP-learned route for the VPC CIDR. Even if the VPN tunnels are healthy, traffic will be dropped at the on-premises router if it has no route back to the VPC, causing asymmetric routing and silent packet loss.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The on-premises network does not have a route to the VPC CIDR (172.16.0.0/16) pointing to the customer gateway — The on-premises network can ping the VPC because the VPC route table has a route to 10.0.0.0/16 pointing to the virtual private gateway (VGW), so return traffic from the VPC is correctly forwarded. However, the VPC cannot ping the on-premises network because the on-premises router lacks a route back to the VPC CIDR (172.16.0.0/16) pointing to the customer gateway (CGW). Without this return route, traffic from the VPC reaches the on-premises network, but the on-premises router drops the response packets as it does not know how to reach 172.16.0.0/16.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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