- A
Use AWS Transit Gateway instead and attach both VPCs.
Why wrong: Transit Gateway also does not support overlapping CIDRs for direct routing; you would need additional configurations.
- B
Verify that the CIDR blocks do not overlap. If they do, you must re-IP one VPC or use other solutions like Transit Gateway with network address translation.
Without overlap, peering works. Overlap requires re-IP or alternative solutions.
- C
Use a NAT gateway in one VPC to translate addresses.
Why wrong: NAT is for outbound traffic, not for solving overlapping CIDRs in peering.
- D
Create the peering connection and add routes for the full CIDR ranges in both route tables.
Why wrong: Overlapping CIDRs cause routing conflicts; peering may not work.
Question 53 of 1,705
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 VPC with CIDR 10.0.0.0/16 and needs to connect to another VPC (192.168.0.0/16) using VPC peering. Both VPCs have overlapping CIDRs with some on-premises networks. What must be done to ensure proper routing?
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
✓
Verify that the CIDR blocks do not overlap. If they do, you must re-IP one VPC or use other solutions like Transit Gateway with network address translation.
VPC peering requires non-overlapping CIDR blocks because AWS uses the destination CIDR to route traffic; if the CIDRs overlap, the route tables cannot distinguish between the two VPCs, causing asymmetric routing or dropped traffic. Option B correctly identifies that overlapping CIDRs must be resolved, either by re-IPing one VPC or using Transit Gateway with NAT capabilities to translate addresses and avoid conflicts.
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.
- ✗
Use AWS Transit Gateway instead and attach both VPCs.
Why it's wrong here
Transit Gateway also does not support overlapping CIDRs for direct routing; you would need additional configurations.
- ✓
Verify that the CIDR blocks do not overlap. If they do, you must re-IP one VPC or use other solutions like Transit Gateway with network address translation.
Why this is correct
Without overlap, peering works. Overlap requires re-IP or alternative solutions.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use a NAT gateway in one VPC to translate addresses.
Why it's wrong here
NAT is for outbound traffic, not for solving overlapping CIDRs in peering.
- ✗
Create the peering connection and add routes for the full CIDR ranges in both route tables.
Why it's wrong here
Overlapping CIDRs cause routing conflicts; peering may not work.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The ANS-C01 exam often tests the misconception that VPC peering can handle overlapping CIDRs by simply adding routes, but the trap is that AWS route tables require unique destination CIDRs for each next-hop, and overlapping ranges cause routing conflicts that break connectivity.
Detailed technical explanation
How to think about this question
Under the hood, VPC peering relies on the VPC route table's destination CIDR to make forwarding decisions; if two VPCs have overlapping CIDRs, the route table cannot uniquely map a destination IP to a single peering attachment, causing packets to be dropped or misrouted. In real-world scenarios, overlapping CIDRs often occur during mergers or acquisitions, where re-IPing is costly; Transit Gateway with a middlebox (e.g., a firewall or NAT appliance) can perform destination NAT (DNAT) to translate overlapping addresses, but this adds complexity and latency. AWS does not support transitive routing through a VPC peering connection, so overlapping CIDRs cannot be resolved by simply adding more specific routes.
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.
Visual reference
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
What to study next
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Verify that the CIDR blocks do not overlap. If they do, you must re-IP one VPC or use other solutions like Transit Gateway with network address translation. — VPC peering requires non-overlapping CIDR blocks because AWS uses the destination CIDR to route traffic; if the CIDRs overlap, the route tables cannot distinguish between the two VPCs, causing asymmetric routing or dropped traffic. Option B correctly identifies that overlapping CIDRs must be resolved, either by re-IPing one VPC or using Transit Gateway with NAT capabilities to translate addresses and avoid conflicts.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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