PCSE Configuring network security Practice Question
This PCSE practice question tests your understanding of configuring network security. 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 uses a hub-and-spoke VPC topology with Network Connectivity Center. The spoke VPCs need to reach the internet. Cloud NAT is configured in the hub VPC. Spoke VPCs have routes to the hub via a VPN tunnel. However, instances in spoke VPCs cannot reach the internet. Which configuration is most likely missing?
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 spoke VPCs are not receiving a default route (0.0.0.0/0) from the hub via Cloud Router.
In a hub-and-spoke topology with Network Connectivity Center, spoke VPCs rely on the hub for internet access via Cloud NAT. For this to work, the spoke VPCs must have a default route (0.0.0.0/0) pointing to the hub, typically advertised by Cloud Router over the VPN tunnel. Without this route, traffic from spoke instances to the internet will not be forwarded to the hub, and thus will not reach Cloud NAT.
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 spoke VPCs are not receiving a default route (0.0.0.0/0) from the hub via Cloud Router.
Why this is correct
Correct: route advertisement needed for spoke to send internet traffic to hub.
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.
✗
A network virtual appliance (NVA) is required in the hub for spoke internet access.
Incorrect: Cloud NAT is in hub, spoke should use hub's NAT via routing.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that Cloud NAT must be deployed in each spoke VPC for internet access, but the trap here is that a centralized Cloud NAT in the hub can work for all spokes if the default route is properly advertised via BGP from the hub.
Detailed technical explanation
How to think about this question
Cloud Router uses BGP to advertise routes to the spoke VPCs over the VPN tunnel. For spoke internet access, the hub must advertise a default route (0.0.0.0/0) with the next hop pointing to the hub's internal IP or the VPN gateway. Without this BGP advertisement, the spoke VPCs will only have their local subnet routes and any custom static routes, so traffic destined for 0.0.0.0/0 will be dropped. In real-world scenarios, this is a common misconfiguration when setting up centralized NAT, as engineers often forget to enable 'Advertise default route' on the Cloud Router or to configure the spoke's route table to accept it.
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 network security — This question tests Configuring network security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The spoke VPCs are not receiving a default route (0.0.0.0/0) from the hub via Cloud Router. — In a hub-and-spoke topology with Network Connectivity Center, spoke VPCs rely on the hub for internet access via Cloud NAT. For this to work, the spoke VPCs must have a default route (0.0.0.0/0) pointing to the hub, typically advertised by Cloud Router over the VPN tunnel. Without this route, traffic from spoke instances to the internet will not be forwarded to the hub, and thus will not reach Cloud NAT.
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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