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 has a VPC network named 'production' with subnets in us-central1 and europe-west1. They have on-premises data centers in New York and London connected via two HA VPN gateways to the respective regions. The on-premises networks use BGP with Cloud Routers in each region. The company also has a Shared VPC with service projects. Recently, they migrated a critical application to Google Cloud, which runs on Compute Engine instances in the europe-west1 subnet. The application needs to communicate with an on-premises database in London reachable via the London VPN. After the migration, the application fails to connect to the database. The Cloud Router in europe-west1 shows that it is receiving the on-premises routes. The instance has a default route to the internet via Cloud NAT. The firewall rules allow all traffic from the instance to the on-premises IP range. What is the most likely cause of the connectivity issue?
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 Cloud Router in europe-west1 has dynamic route import from BGP disabled.
The Cloud Router in europe-west1 is receiving the on-premises routes via BGP, but if dynamic route import from BGP is disabled, those routes are not installed into the VPC route table. Without the specific route for the London on-premises database subnet, traffic from the Compute Engine instance will not be forwarded to the VPN tunnel, causing the connection failure. The default route via Cloud NAT only handles internet-bound traffic, not traffic destined for on-premises IP ranges.
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 on-premises firewall is blocking traffic from the Google Cloud IP ranges.
Why it's wrong here
Incorrect: the question states it's a route propagation issue, not firewall.
✗
The Cloud NAT is incorrectly configured and blocking traffic to on-premises IP ranges.
Why it's wrong here
Incorrect: Cloud NAT only applies to traffic with destination outside VPC, but on-premises ranges are not internet.
✗
The Shared VPC configuration prevents service project instances from using VPC routes.
Why it's wrong here
Incorrect: Shared VPC allows service project instances to use host project routes.
✓
The Cloud Router in europe-west1 has dynamic route import from BGP disabled.
Why this is correct
Correct: without dynamic route import, learned BGP routes are not added to the VPC route table.
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 distinction between BGP session establishment (routes received) and route installation (routes imported into the VPC route table), leading candidates to assume that receiving BGP routes automatically means they are usable for forwarding.
Detailed technical explanation
How to think about this question
Cloud Routers use BGP to exchange routes with on-premises routers, but the routes must be imported into the VPC route table via the 'import custom routes' or 'import dynamic routes' setting. If this setting is disabled, BGP-learned routes are not added to the VPC, and the VPN tunnel will not have a corresponding route for the on-premises subnet. This is a common misconfiguration when setting up HA VPN, as the Cloud Router's dynamic route import is enabled by default but can be inadvertently disabled during advanced configuration or when using custom route advertisements.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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 Cloud Router in europe-west1 has dynamic route import from BGP disabled. — The Cloud Router in europe-west1 is receiving the on-premises routes via BGP, but if dynamic route import from BGP is disabled, those routes are not installed into the VPC route table. Without the specific route for the London on-premises database subnet, traffic from the Compute Engine instance will not be forwarded to the VPN tunnel, causing the connection failure. The default route via Cloud NAT only handles internet-bound traffic, not traffic destined for on-premises IP ranges.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This PCSE practice question is part of Courseiva's free Google Cloud 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 PCSE exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.