The answer is that no additional networking configuration is required because the shared subnet remains part of the owner’s VPC. When you use AWS Resource Access Manager to share a subnet, you are not creating a separate network; you are simply granting other accounts the ability to launch resources into a logical subdivision of the same VPC’s CIDR block. Since all instances—whether launched by the owner or by a participant account—reside within the same VPC, the VPC’s internal router already enables private IP communication between them by default. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this concept tests your understanding that subnet sharing via RAM does not introduce any new routing, peering, or VPN requirements; a common trap is assuming that cross-account access necessitates a VPC peering or transit gateway. Remember the key insight: sharing a subnet is like lending a room in your house—the room is still part of your house, so no new doors or hallways are needed.
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 is designing a network for a multi-account architecture using AWS Resource Access Manager (RAM) to share VPC subnets across accounts. They want to ensure that instances in shared subnets can communicate with instances in the owner's VPC using private IP addresses. What is required?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
No additional networking configuration is required; the shared subnet is part of the same VPC.
When you share a subnet using AWS Resource Access Manager (RAM), the shared subnet is part of the owner's VPC. Instances launched into that shared subnet reside in the same VPC as the owner's instances, so they can communicate using private IP addresses by default, with no additional networking configuration required. This is because VPC subnets are a logical subdivision of the VPC's CIDR block, and all instances within the same VPC can route to each other via the VPC's internal router.
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.
✗
Establish a VPC peering connection between the owner and participant accounts.
Why it's wrong here
Not needed; they are in the same VPC.
✗
Configure a VPC endpoint for Amazon EC2 to allow cross-account private communication.
Why it's wrong here
Not needed for same VPC communication.
✓
No additional networking configuration is required; the shared subnet is part of the same VPC.
Why this is correct
Shared subnets are within the same VPC, so routing is inherent.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a transit gateway and attach both VPCs to it.
Why it's wrong here
They are in the same VPC, no transit gateway needed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates mistakenly think cross-account subnet sharing requires additional connectivity like VPC peering or a transit gateway, when in fact the shared subnet is logically part of the same VPC, so no extra networking is needed for private IP communication.
Detailed technical explanation
How to think about this question
Under the hood, AWS RAM shares the subnet as a resource, but the subnet remains part of the owner's VPC and uses the same VPC router and route tables. Participant accounts can launch resources into the shared subnet, and those resources receive IP addresses from the VPC's CIDR, allowing direct Layer 3 communication with owner instances without any gateway or peering. A subtle behavior is that participant accounts cannot view or modify the VPC's route tables or security group rules owned by the owner, but they can reference security groups from the owner account if the owner shares them via RAM.
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 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: No additional networking configuration is required; the shared subnet is part of the same VPC. — When you share a subnet using AWS Resource Access Manager (RAM), the shared subnet is part of the owner's VPC. Instances launched into that shared subnet reside in the same VPC as the owner's instances, so they can communicate using private IP addresses by default, with no additional networking configuration required. This is because VPC subnets are a logical subdivision of the VPC's CIDR block, and all instances within the same VPC can route to each other via the VPC's internal router.
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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Question Discussion
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