- A
Delete the VPC peering connection and use a VPN instead.
Why wrong: This would not resolve the routing conflict and would break connectivity between VPCs.
- B
Update the on-premises router to advertise a more specific prefix for the new VPC over Direct Connect, such as 10.0.1.0/24, and ensure the new VPC's route table has a route to the on-premises network.
A more specific BGP advertisement will take precedence, directing traffic to the correct VPC.
- C
Configure the VPC peering connection to propagate routes to the Direct Connect virtual interface.
Why wrong: VPC peering does not support route propagation across Direct Connect.
- D
Disable route propagation on the VPC route tables and add static routes.
Why wrong: Disabling propagation would remove all propagated routes, which may break connectivity.
Quick Answer
The correct answer is to update the on-premises router to advertise a more specific prefix for the new VPC over Direct Connect, such as 10.0.1.0/24, and ensure the new VPC’s route table has a route to the on-premises network. This resolves the overlapping CIDR issue because BGP routes learned over Direct Connect are more specific than VPC peering routes, and AWS always prefers the most specific matching route in the route table. When both VPCs share the same 10.0.0.0/16 block, the on-premises advertisement of the full /16 directs traffic to the old VPC, but a more specific prefix like /24 overrides that and steers traffic to the new VPC. On the ANS-C01 exam, this scenario tests your understanding of route priority between Direct Connect and VPC peering, a common trap where candidates forget that VPC peering does not support transitive routing or that disabling route propagation would break all on-premises connectivity. Memory tip: “Specific beats general—advertise a narrower prefix to fix overlapping CIDR.”
ANS-C01 Network Implementation Practice Question
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.
A company has a Direct Connect connection with a private VIF to a VPC. The on-premises network uses BGP to advertise a specific prefix (10.0.0.0/16) to the VPC. Recently, the company deployed a new VPC with CIDR 10.0.0.0/16 in a different region and established a VPC peering connection between the two VPCs. Now, traffic from on-premises to the new VPC is being routed to the old VPC instead. How should the company resolve this issue?
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
Update the on-premises router to advertise a more specific prefix for the new VPC over Direct Connect, such as 10.0.1.0/24, and ensure the new VPC's route table has a route to the on-premises network.
Option B is correct because the BGP advertisement of 10.0.0.0/16 over Direct Connect is more specific and takes precedence over the VPC peering route. By advertising a more specific prefix (e.g., 10.0.1.0/24) for the new VPC over Direct Connect or adjusting the route propagation, traffic can be directed correctly. Option A is wrong because deleting the peering connection would break connectivity between VPCs. Option C is wrong because VPC peering does not support transitive routing. Option D is wrong because disabling route propagation would remove all propagated routes, including the correct ones.
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.
- ✗
Delete the VPC peering connection and use a VPN instead.
Why it's wrong here
This would not resolve the routing conflict and would break connectivity between VPCs.
- ✓
Update the on-premises router to advertise a more specific prefix for the new VPC over Direct Connect, such as 10.0.1.0/24, and ensure the new VPC's route table has a route to the on-premises network.
- ✗
Configure the VPC peering connection to propagate routes to the Direct Connect virtual interface.
Why it's wrong here
VPC peering does not support route propagation across Direct Connect.
- ✗
Disable route propagation on the VPC route tables and add static routes.
Why it's wrong here
Disabling propagation would remove all propagated routes, which may break connectivity.
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 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 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.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
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: Update the on-premises router to advertise a more specific prefix for the new VPC over Direct Connect, such as 10.0.1.0/24, and ensure the new VPC's route table has a route to the on-premises network. — Option B is correct because the BGP advertisement of 10.0.0.0/16 over Direct Connect is more specific and takes precedence over the VPC peering route. By advertising a more specific prefix (e.g., 10.0.1.0/24) for the new VPC over Direct Connect or adjusting the route propagation, traffic can be directed correctly. Option A is wrong because deleting the peering connection would break connectivity between VPCs. Option C is wrong because VPC peering does not support transitive routing. Option D is wrong because disabling route propagation would remove all propagated routes, including the correct ones.
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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Last reviewed: Jun 20, 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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