The answer is that the Transit Gateway owner must accept the shared attachment. When a Transit Gateway is shared via AWS Resource Access Manager, the owner account must explicitly accept the VPC attachment request from the spoke account; until that acceptance occurs, the attachment remains in an 'available' state but is not associated with a Transit Gateway route table in the owner’s account, so traffic cannot be routed through it. This scenario tests your understanding of the cross-account Transit Gateway attachment workflow, a common trap on the AWS Certified Advanced Networking Specialty ANS-C01 exam where candidates mistake 'available' for fully functional. Remember that 'available' means the attachment is provisioned but not yet accepted and associated—think of it as "available for acceptance," not "available for traffic." A useful memory tip: "Accept before you associate, associate before you route."
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 large enterprise uses AWS Organizations with multiple accounts. The central networking account hosts a Transit Gateway with attachments from VPCs in various accounts. The enterprise uses AWS Resource Access Manager (RAM) to share the Transit Gateway with other accounts. A network engineer in a spoke account creates a VPC and attaches it to the shared Transit Gateway. The attachment shows 'available' state. However, traffic from the spoke VPC to other attached VPCs fails. The spoke VPC route table has a route to the Transit Gateway for 0.0.0.0/0. The Transit Gateway route table has routes for the spoke VPC CIDR and other VPC CIDRs. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Transit Gateway owner has not accepted the VPC attachment
When a Transit Gateway is shared via RAM, the owner account must accept the attachment request. The attachment shows 'available' but not 'associated'? Actually, for shared TGW, the owner account needs to accept the attachment. The attachment state 'available' means it's ready but not yet associated with a TGW route table in the owner's account. The owner must associate it. Option B is wrong because the TGW route table has routes. Option C is wrong because the spoke route table has a route. Option D is wrong because no cross-account roles are needed for attachment.
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 spoke account does not have an IAM role to access the Transit Gateway
Why it's wrong here
No IAM role needed; RAM sharing handles permissions.
✗
The spoke VPC route table does not have routes to the other VPC CIDRs
Why it's wrong here
The question states route to TGW for 0.0.0.0/0, which should cover all destinations.
✗
The Transit Gateway route table does not propagate routes from the spoke VPC attachment
Why it's wrong here
Propagation is not required for static routes; but the attachment must be associated.
✓
The Transit Gateway owner has not accepted the VPC attachment
Why this is correct
Shared TGW attachments must be accepted by owner.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
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: The Transit Gateway owner has not accepted the VPC attachment — When a Transit Gateway is shared via RAM, the owner account must accept the attachment request. The attachment shows 'available' but not 'associated'? Actually, for shared TGW, the owner account needs to accept the attachment. The attachment state 'available' means it's ready but not yet associated with a TGW route table in the owner's account. The owner must associate it. Option B is wrong because the TGW route table has routes. Option C is wrong because the spoke route table has a route. Option D is wrong because no cross-account roles are needed for attachment.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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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 deployed a multi-account AWS environment using AWS Organizations. Each account has one or more VPCs that need to communicate with each other and with an on-premises data center via a central transit VPC. The company uses AWS Transit Gateway with a centralized network account that hosts the Transit Gateway. VPCs from other accounts are attached to the Transit Gateway via Resource Access Manager (RAM) shares. The network team notices that after attaching a new VPC from a member account, resources in that VPC cannot communicate with resources in other attached VPCs. The Transit Gateway route tables have appropriate routes, and the VPC route tables point to the Transit Gateway. What is the MOST likely cause of the issue?
hard
✓ A.The Transit Gateway attachment in the member account is in the 'pending acceptance' state and not yet accepted by the Transit Gateway owner.
B.The Transit Gateway route table does not have the routes from the new VPC propagated.
C.The new VPC's CIDR overlaps with an existing attachment's CIDR.
D.The member account's VPC does not have a route to the Transit Gateway in its route tables.
Why A: Option D is correct because when sharing a Transit Gateway attachment via RAM, the owner of the Transit Gateway must accept the attachment. Option A is incorrect because the Transit Gateway is not in the member account. Option B is incorrect because route propagation is not required. Option C is incorrect because VPC CIDR is not the issue.
Last reviewed: Jun 20, 2026
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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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