- A
The requester must accept the peering connection with the 'Enable DNS Resolution' option checked.
The requester can enable DNS resolution when creating the peering connection.
- B
Both VPCs must have the 'Enable DNS Resolution' attribute set to true in their VPC settings.
Each VPC must have DNS resolution enabled for instances to use DNS.
- C
Ensure both VPCs are in the same AWS region.
Why wrong: DNS resolution across peering works for both intra-region and cross-region peering.
- D
The accepter must modify the peering connection to enable DNS resolution from their side.
Why wrong: Only the requester can enable DNS resolution; the accepter cannot modify that setting.
- E
The route tables must include a route for the peered VPC's CIDR.
Why wrong: Route tables are needed for connectivity but not specifically for DNS resolution.
Quick Answer
The answer is that both VPCs must have the 'Enable DNS Resolution' attribute set to true in their VPC settings, and the requester must accept the peering connection with DNS resolution enabled. This works because DNS resolution across a VPC peering connection relies on the Amazon-provided DNS server in each VPC being able to resolve private hostnames from the peered VPC’s CIDR, which requires the DNS resolution attribute to be enabled on both sides and the peering connection itself to be configured to support it. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this concept tests your understanding of how VPC peering handles DNS, often appearing as a trap where candidates mistakenly think DNS settings are configured at the VPC level rather than the peering connection level. A common memory tip is to remember that DNS resolution is a peering-level toggle, not a VPC-level toggle—think of it as a two-way handshake where both sides must opt in.
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.
A company has a VPC with a CIDR of 10.0.0.0/16. They have created a VPC peering connection with another VPC (CIDR 10.1.0.0/16). They want to enable DNS resolution between the VPCs. Which TWO actions must be taken?
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
The requester must accept the peering connection with the 'Enable DNS Resolution' option checked.
Options B and D are correct. To enable DNS resolution across a VPC peering connection, the requester must accept the peering connection with DNS resolution enabled, and the accepter must update the route tables. Option A is wrong because the VPCs must be in the same region? Actually, cross-region peering is allowed. Option C is wrong because the accepter does not need to modify the peering connection. Option E is wrong because DNS resolution settings are at the peering connection level, not the VPC level.
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 requester must accept the peering connection with the 'Enable DNS Resolution' option checked.
- ✓
Both VPCs must have the 'Enable DNS Resolution' attribute set to true in their VPC settings.
- ✗
Ensure both VPCs are in the same AWS region.
Why it's wrong here
DNS resolution across peering works for both intra-region and cross-region peering.
- ✗
The accepter must modify the peering connection to enable DNS resolution from their side.
Why it's wrong here
Only the requester can enable DNS resolution; the accepter cannot modify that setting.
- ✗
The route tables must include a route for the peered VPC's CIDR.
Why it's wrong here
Route tables are needed for connectivity but not specifically for DNS resolution.
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 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 requester must accept the peering connection with the 'Enable DNS Resolution' option checked. — Options B and D are correct. To enable DNS resolution across a VPC peering connection, the requester must accept the peering connection with DNS resolution enabled, and the accepter must update the route tables. Option A is wrong because the VPCs must be in the same region? Actually, cross-region peering is allowed. Option C is wrong because the accepter does not need to modify the peering connection. Option E is wrong because DNS resolution settings are at the peering connection level, not the VPC level.
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.
About these practice questions
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Same concept, more angles
1 more ways this is tested on ANS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company has a VPC with a CIDR of 10.0.0.0/16. They have set up a VPC peering connection with another VPC (CIDR 172.16.0.0/16). The route tables are configured correctly. However, instances in the first VPC cannot communicate with instances in the peered VPC. The security groups and network ACLs are configured to allow all traffic. What is the most likely cause?
hard- ✓ A.The DNS resolution settings for the VPC peering connection are not enabled.
- B.The route tables in the VPCs are not propagated to the subnets.
- C.The instances do not have ICMP traffic allowed.
- D.The VPC CIDR ranges overlap.
Why A: Option B is correct because DNS resolution settings for VPC peering must be enabled for instances to resolve DNS hostnames across the peering connection. Option A is wrong because route tables are already configured correctly. Option C is wrong because the CIDRs are different and non-overlapping. Option D is wrong because ICMP is not required for basic connectivity.
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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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