- A
The route tables are not propagated
Why wrong: Route tables not propagated is incorrect because the route tables are stated to be correct, so propagation is not the issue.
- B
VPC peering does not support ICMP
Why wrong: VPC peering does support ICMP. This statement is false and is a common misconception.
- C
The VPCs are in different regions
Why wrong: The VPCs being in different regions is not a problem because inter-region VPC peering supports ICMP and is a standard feature.
- D
The security groups are blocking ICMP
Security groups are blocking ICMP is the most likely cause. Even if security groups allow other traffic, ICMP requires a specific rule for inbound ICMP (type 8, code 0 for echo request). Without that rule, ping fails.
Question 1,387 of 1,705
VPC Peering Protocol Support — ICMP Not Allowed | AWS Advanced Networking Specialty Explained
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. A key principle to apply: vPC Peering. 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 network engineer is troubleshooting connectivity between two VPCs that are peered. The route tables are correct, and security groups allow traffic. However, ICMP ping fails. 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.
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 security groups are blocking ICMP
VPC peering does support ICMP traffic. The most common reason for ICMP ping failure despite correct route tables and security groups that allow traffic is that the security groups are not explicitly allowing ICMP. Security groups default to deny all inbound traffic, and a rule allowing all TCP traffic does not include ICMP. Therefore, the security groups must have an inbound ICMP rule for the ping to succeed.
Key principle: VPC Peering
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 route tables are not propagated
Why it's wrong here
Route tables not propagated is incorrect because the route tables are stated to be correct, so propagation is not the issue.
- ✗
VPC peering does not support ICMP
Why it's wrong here
VPC peering does support ICMP. This statement is false and is a common misconception.
- ✗
The VPCs are in different regions
Why it's wrong here
The VPCs being in different regions is not a problem because inter-region VPC peering supports ICMP and is a standard feature.
- ✓
The security groups are blocking ICMP
Why this is correct
Security groups are blocking ICMP is the most likely cause. Even if security groups allow other traffic, ICMP requires a specific rule for inbound ICMP (type 8, code 0 for echo request). Without that rule, ping fails.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
VPC Peering
Common exam traps
Common exam trap: answer the scenario, not the keyword
The ANS-C01 exam often tests the misconception that VPC peering does not support ICMP. In reality, VPC peering supports ICMP; the issue is typically with security group or network ACL configuration not permitting ICMP.
Detailed technical explanation
How to think about this question
VPC peering operates at the layer 3/4 level, forwarding traffic based on the destination IP and protocol; it does not inspect or forward ICMP packets unless explicitly allowed via a network ACL or security group, but the peering itself does not support ICMP echo requests. In practice, ICMP is often blocked by default in VPC peering due to the lack of a specific allow rule in the peering connection's route table or the underlying hypervisor's filtering, though AWS documentation confirms that ICMP is not supported over VPC peering connections.
KKey Concepts to Remember
- VPC Peering
- ICMP
- Security Group
- Explicit Allow Rule
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
VPC Peering
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 vPC Peering, then practise related ANS-C01 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — VPC Peering.
What is the correct answer to this question?
The correct answer is: The security groups are blocking ICMP — VPC peering does support ICMP traffic. The most common reason for ICMP ping failure despite correct route tables and security groups that allow traffic is that the security groups are not explicitly allowing ICMP. Security groups default to deny all inbound traffic, and a rule allowing all TCP traffic does not include ICMP. Therefore, the security groups must have an inbound ICMP rule for the ping to succeed.
What should I do if I get this ANS-C01 question wrong?
Review vPC Peering, then practise related ANS-C01 questions on the same topic to reinforce the concept.
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?
VPC Peering
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Last reviewed: Jul 4, 2026
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.
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