The correct answer is that the subnet has a VPN connection to a network with CIDR 172.31.0.0/16. This is determined by analyzing the VPC route table for VPN connectivity, which reveals a specific route pointing to a virtual private gateway (vgw) for the destination 172.31.0.0/16, alongside a local VPC route and a default route to an Internet Gateway. The presence of this targeted VPN gateway route directly indicates an established VPN connection to a remote network with that CIDR block. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your ability to interpret route tables and distinguish between VPN, Direct Connect, and Transit Gateway attachments—a common trap is confusing a VPN gateway route with a Transit Gateway route or assuming a default route to an IGW makes a subnet private. Remember the memory tip: “A route to a vgw means a VPN is in play; a route to a tgw means a Transit Gateway is the way.”
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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. The following is an excerpt from a VPC route table:
Destination | Target
10.0.0.0/16 | local
0.0.0.0/0 | igw-1234567890abcdef0
172.31.0.0/16 | vgw-1234567890abcdef0
Based on the route table, which of the following is true?
Refer to the exhibit. The following is an excerpt from a VPC route table:
Destination | Target
10.0.0.0/16 | local
0.0.0.0/0 | igw-1234567890abcdef0
172.31.0.0/16 | vgw-1234567890abcdef0
A
The route table is the main route table for the VPC
Why wrong: There is no indication that it is the main route table; it could be a custom route table.
B
The subnet is connected to a Transit Gateway
Why wrong: The target is vgw-..., which is a Virtual Private Gateway, not Transit Gateway.
C
The subnet has a VPN connection to a network with CIDR 172.31.0.0/16
The route to vgw for 172.31.0.0/16 indicates a VPN connection.
D
The subnet is a private subnet with no internet access
Why wrong: There is a default route to an Internet Gateway, so the subnet has internet access.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The subnet has a VPN connection to a network with CIDR 172.31.0.0/16
Option C is correct because the route table has a local route for the VPC CIDR, a default route to an Internet Gateway, and a route to a VPN Gateway (vgw) for a different CIDR (172.31.0.0/16). This indicates a VPN connection to a network with that CIDR. Option A is wrong because there is no route to a Transit Gateway. Option B is wrong because there is a route to an Internet Gateway, so it is not a private subnet. Option D is wrong because the route table is associated with a subnet, not a VPC.
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 route table is the main route table for the VPC
Why it's wrong here
There is no indication that it is the main route table; it could be a custom route table.
✗
The subnet is connected to a Transit Gateway
Why it's wrong here
The target is vgw-..., which is a Virtual Private Gateway, not Transit Gateway.
✓
The subnet has a VPN connection to a network with CIDR 172.31.0.0/16
Why this is correct
The route to vgw for 172.31.0.0/16 indicates a VPN connection.
The subnet is a private subnet with no internet access
Why it's wrong here
There is a default route to an Internet Gateway, so the subnet has internet access.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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 ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Network Design — This question tests Network Design — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The subnet has a VPN connection to a network with CIDR 172.31.0.0/16 — Option C is correct because the route table has a local route for the VPC CIDR, a default route to an Internet Gateway, and a route to a VPN Gateway (vgw) for a different CIDR (172.31.0.0/16). This indicates a VPN connection to a network with that CIDR. Option A is wrong because there is no route to a Transit Gateway. Option B is wrong because there is a route to an Internet Gateway, so it is not a private subnet. Option D is wrong because the route table is associated with a subnet, not a VPC.
What should I do if I get this ANS-C01 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 ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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