The answer is the missing roles/iap.tunnelResourceAccessor role. When you use Cloud Console SSH to connect to a Compute Engine instance, Google Cloud now routes that connection through Identity-Aware Proxy (IAP) TCP forwarding by default, which acts as a gatekeeper at the network edge. Even with the Compute Admin role, which grants broad compute permissions, the IAP layer enforces its own access control; without the iap.tunnelResourceAccessor role, the IAP proxy denies the connection with a 403 Forbidden error before it ever reaches the instance. On the Google Professional Cloud Security Engineer exam, this question tests your understanding that IAP TCP forwarding is a separate authorization boundary from compute-level roles—a common trap is assuming Compute Admin covers all SSH access. Remember: IAP is the bouncer at the door, and Compute Admin is just a VIP pass inside the club; you need the IAP key to get past the door. Memory tip: “IAP Accessor or 403 Forbidden.”
PCSE Practice Question: Configuring access within a cloud solution environment
This PCSE practice question tests your understanding of configuring access within a cloud solution environment. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 user receives a "403 Forbidden" error when trying to access a Compute Engine instance via SSH from the Cloud Console. The user has the Compute Admin role on the project. 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 user does not have the roles/iap.tunnelResourceAccessor role.
The 403 Forbidden error when using Cloud Console SSH indicates that Identity-Aware Proxy (IAP) TCP forwarding is being used, which requires the roles/iap.tunnelResourceAccessor role. Even with Compute Admin, the user lacks this IAP-specific role, so the request is denied at the IAP layer before reaching the instance.
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.
✗
The user does not have the compute.instances.setMetadata permission.
Why it's wrong here
Compute Admin includes this permission.
✗
The firewall rules do not allow SSH from the user's IP.
Why it's wrong here
Cloud Console SSH goes through IAP, not direct IP.
✗
OS Login is enabled on the instance and the user lacks the osLogin role.
Why it's wrong here
This could be a cause but IAP access is more common.
✓
The user does not have the roles/iap.tunnelResourceAccessor role.
Why this is correct
Cloud Console SSH uses IAP TCP forwarding, which requires this role.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that Compute Admin or firewall rules are sufficient for Cloud Console SSH, when in reality IAP requires a distinct role (roles/iap.tunnelResourceAccessor) that is not included in Compute Admin.
Detailed technical explanation
How to think about this question
IAP TCP forwarding works by creating a secure tunnel from the user's browser through Google's infrastructure to the Compute Engine instance, using the gcloud compute start-iap-tunnel command under the hood. The roles/iap.tunnelResourceAccessor role grants the iam.serviceAccounts.actAs permission on the instance's service account, which is required to initiate the tunnel. Without this role, the IAP proxy returns a 403 error even if the user has Compute Admin, because IAP authorization is separate from compute permissions.
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.
Configuring access within a cloud solution environment — This question tests Configuring access within a cloud solution environment — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The user does not have the roles/iap.tunnelResourceAccessor role. — The 403 Forbidden error when using Cloud Console SSH indicates that Identity-Aware Proxy (IAP) TCP forwarding is being used, which requires the roles/iap.tunnelResourceAccessor role. Even with Compute Admin, the user lacks this IAP-specific role, so the request is denied at the IAP layer before reaching the instance.
What should I do if I get this PCSE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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Question Discussion
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