The answer is a private subnet with no route to an Internet Gateway, where the default route either points to a non-responsive NAT instance or is missing entirely. This conclusion is drawn from the traceroute output, which stops at the VPC router’s IP (10.0.0.1) after the first hop to the subnet’s default gateway (10.0.1.1). In a VPC, the VPC router performs routing between subnets but does not forward traffic to the internet unless a default route via an Internet Gateway or NAT device exists; the absence of a third hop to a public IP or a NAT device’s private IP confirms that no such route is active. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your ability to interpret traceroute behavior as a diagnostic tool for VPC routing configurations—a common trap is assuming a missing hop means a network failure, when it actually reveals the subnet’s lack of internet path. Memory tip: if the traceroute dies at the VPC router, the subnet is “router-locked”—no IGW or NAT in the route table.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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.
Exhibit
Refer to the exhibit.
CLI output from an EC2 instance:
[ec2-user@ip-10-0-1-5 ~]$ traceroute 8.8.8.8
traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets
1 10.0.1.1 (10.0.1.1) 1.123 ms 1.089 ms 1.045 ms
2 10.0.0.1 (10.0.0.1) 1.234 ms 1.198 ms 1.167 ms
3 * * *
4 * * *
...
The EC2 instance has a private IP 10.0.1.5. The first two hops are 10.0.1.1 (the subnet's default gateway) and 10.0.0.1. Based on the traceroute, what is the most likely configuration of the VPC?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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.
Refer to the exhibit.
CLI output from an EC2 instance:
[ec2-user@ip-10-0-1-5 ~]$ traceroute 8.8.8.8
traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets
1 10.0.1.1 (10.0.1.1) 1.123 ms 1.089 ms 1.045 ms
2 10.0.0.1 (10.0.0.1) 1.234 ms 1.198 ms 1.167 ms
3 * * *
4 * * *
...
A
The subnet is a public subnet with a route to an Internet Gateway
Why wrong: If public, traceroute would show the IGW.
B
The subnet is a private subnet with no route to an Internet Gateway, and the default route points to a NAT instance or is missing
Traffic stops at VPC router, indicating no internet path.
C
The subnet is a private subnet with a route to a NAT Gateway
Why wrong: NAT Gateway would likely appear as a hop.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The subnet is a private subnet with no route to an Internet Gateway, and the default route points to a NAT instance or is missing
The traceroute shows the first hop as 10.0.1.1 (the subnet's default gateway) and the second hop as 10.0.0.1 (the VPC router's IP for the main route table). The absence of a third hop to a public IP or NAT device indicates that the instance's traffic is not being forwarded beyond the VPC router. This is consistent with a private subnet that has no route to an Internet Gateway and either has no default route or a default route pointing to a NAT instance that is not responding or is missing, causing the traceroute to stop at the VPC router.
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 subnet is a public subnet with a route to an Internet Gateway
Why it's wrong here
If public, traceroute would show the IGW.
✓
The subnet is a private subnet with no route to an Internet Gateway, and the default route points to a NAT instance or is missing
Why this is correct
Traffic stops at VPC router, indicating no internet path.
Clue confirmation
The clue words "first", "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The subnet is a private subnet with a route to a NAT Gateway
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a private subnet must have a NAT Gateway or NAT instance for outbound traffic, but the traceroute's lack of a third hop indicates that either no NAT device exists or the default route is missing entirely, not that a NAT device is present but unresponsive.
Trap categories for this question
Command / output trap
If public, traceroute would show the IGW.
Detailed technical explanation
How to think about this question
In AWS, the VPC router (the .1 address of the VPC's CIDR block) is the implicit router that handles traffic between subnets and to gateways. When a subnet has no route to an Internet Gateway or NAT device, the VPC router drops traffic destined for the Internet, causing traceroute to time out after the second hop. This behavior is distinct from a NAT Gateway, which would respond with its own private IP as the next hop, and from an Internet Gateway, which would forward traffic to the public Internet.
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.
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 Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The subnet is a private subnet with no route to an Internet Gateway, and the default route points to a NAT instance or is missing — The traceroute shows the first hop as 10.0.1.1 (the subnet's default gateway) and the second hop as 10.0.0.1 (the VPC router's IP for the main route table). The absence of a third hop to a public IP or NAT device indicates that the instance's traffic is not being forwarded beyond the VPC router. This is consistent with a private subnet that has no route to an Internet Gateway and either has no default route or a default route pointing to a NAT instance that is not responding or is missing, causing the traceroute to stop at the VPC router.
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: "first", "most likely". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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