The answer is that internet-bound traffic from the subnet will be routed through the NAT Gateway nat-67890. This is correct because when a subnet is created without an explicit route table association, it automatically inherits the VPC’s main route table, which in this case is rtb-12345. That main route table contains a default route (0.0.0.0/0) pointing to the NAT Gateway, so all outbound internet traffic from that subnet follows that path. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of implicit subnet routing and the critical distinction between main and custom route tables. A common trap is assuming a subnet without an explicit association has no internet path, or confusing the local route with a default route. Remember: no explicit association means the subnet defaults to the main table, and the main table’s 0.0.0.0/0 target dictates the default route. A quick memory tip: “No explicit tie? Main table’s your guide—check its default for where traffic will ride.”
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. 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.
Refer to the exhibit. A subnet is created in VPC vpc-abcde but no explicit route table association is set. What is the default route for internet-bound traffic from this subnet?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Traffic goes through the NAT Gateway nat-67890.
Option C is correct because the subnet inherits the main route table (rtb-12345) which has a route to a NATGateway for 0.0.0.0/0. Option A is wrong because the local route is for VPC internal traffic. Option B is wrong because an Internet Gateway is not present. Option D is wrong because no explicit association exists.
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.
✗
Traffic is dropped because no explicit association is set.
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 Implementation — This question tests Network Implementation — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Traffic goes through the NAT Gateway nat-67890. — Option C is correct because the subnet inherits the main route table (rtb-12345) which has a route to a NAT Gateway for 0.0.0.0/0. Option A is wrong because the local route is for VPC internal traffic. Option B is wrong because an Internet Gateway is not present. Option D is wrong because no explicit association exists.
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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Question Discussion
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