- A
Change the static route priority to 1000 to match dynamic routes.
Why wrong: Dynamic routes have priority 1000, so changing static to 1000 would not help; the static route would still have same priority but less specific dynamic route would win for more specific subnets? Actually, dynamic routes have a lower priority (higher number) than static, so dynamic routes are preferred. The issue is not priority but propagation.
- B
Verify that the Cloud Router is advertising the 10.1.0.0/24 subnet to on-premises.
The Cloud Router may not automatically advertise new subnets unless configured to do so via custom advertisements.
- C
Verify that the new subnet's range is allowed in the on-premises firewall and route tables.
The on-premises network may have routing or firewall rules preventing traffic to the new subnet.
- D
Delete the static route for 10.0.0.0/8 and rely solely on dynamic routing.
Why wrong: While possible, it may break connectivity for other subnets in the range that are not advertised dynamically.
- E
Check the BGP session status between the Cloud Router and the on-premises router.
The BGP session may be down, so no routes are exchanged.
Quick Answer
The correct answer involves checking the BGP session status, verifying Cloud Router advertisements, and inspecting on-premises route tables. This is because the static route priority overriding dynamic routes creates a subtle issue: while the static route for 10.0.0.0/8 with priority 100 is more preferred than the default dynamic route priority of 1000, the new subnet 10.1.0.0/24 is a more specific prefix, so longest-prefix-match routing should still direct traffic correctly. However, if the Cloud Router fails to advertise the new subnet via BGP, or if the on-premises router does not accept the update, the on-premises network will lack a route for 10.1.0.0/24, causing traffic failure. This scenario tests your understanding of BGP route propagation, route priority, and prefix specificity in Google Cloud—a common trap where candidates mistakenly focus on static route priority instead of verifying BGP advertisement. On the Google Professional Cloud Network Engineer exam, remember: static routes with lower priority win over dynamic routes for the same prefix, but more specific prefixes always override less specific ones. Memory tip: “Specificity beats priority—always check BGP is actually talking.”
PCNE Implementing a Virtual Private Cloud Practice Question
This PCNE practice question tests your understanding of implementing a virtual private cloud. 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 that is connected to an on-premises network via a Cloud VPN tunnel using dynamic routing (BGP). They have set up a Cloud Router with an advertised IP range of 10.0.0.0/8. The on-premises network advertises 172.16.0.0/12. They also have a custom static route in the VPC for 10.0.0.0/8 that points to a next-hop VPN tunnel (the same tunnel) with priority 100. Recently, they added a new subnet 10.1.0.0/24 in the VPC. Traffic from on-premises to 10.1.0.0/24 is not working. Which THREE steps should they take to troubleshoot and resolve the issue? (Choose 3.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Verify that the Cloud Router is advertising the 10.1.0.0/24 subnet to on-premises.
The issue is that the static route for 10.0.0.0/8 with priority 100 may be overwriting the dynamically learned routes for the new subnet. Dynamic routes from Cloud Router have a higher priority (1000) by default, but the static route with lower priority (100) will take precedence. However, since the static route points to the same VPN tunnel, it should still work, but if the static route is for the entire range, it may not be specific enough for the new subnet? Actually, the most specific route wins. The subnet 10.1.0.0/24 is more specific than 10.0.0.0/8, so a dynamic route for 10.1.0.0/24 should be propagated. But since the static route covers 10.0.0.0/8, it does not prevent more specific routes. The problem might be that the Cloud Router is not advertising the new subnet to on-premises, or the on-premises router is not accepting the update, or the BGP session is down. Option A is correct: check if the Cloud Router is advertising the subnet. Option B is correct: check the BGP session status. Option E is correct: check on-premises route tables. Option C is incorrect because changing priority might not help, and Option D is incorrect because you can keep the static route for other subnets.
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.
- ✗
Change the static route priority to 1000 to match dynamic routes.
Why it's wrong here
Dynamic routes have priority 1000, so changing static to 1000 would not help; the static route would still have same priority but less specific dynamic route would win for more specific subnets? Actually, dynamic routes have a lower priority (higher number) than static, so dynamic routes are preferred. The issue is not priority but propagation.
- ✓
Verify that the Cloud Router is advertising the 10.1.0.0/24 subnet to on-premises.
Why this is correct
The Cloud Router may not automatically advertise new subnets unless configured to do so via custom advertisements.
Related concept
CIDR notation defines the prefix length.
- ✓
Verify that the new subnet's range is allowed in the on-premises firewall and route tables.
- ✗
Delete the static route for 10.0.0.0/8 and rely solely on dynamic routing.
Why it's wrong here
While possible, it may break connectivity for other subnets in the range that are not advertised dynamically.
- ✓
Check the BGP session status between the Cloud Router and the on-premises router.
Common exam traps
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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 PCNE subnetting questions on CIDR, address ranges, and subnet selection.
- →
Implementing a Virtual Private Cloud — study guide chapter
Learn the concepts, then practise the questions
- →
Implementing a Virtual Private Cloud practice questions
Targeted practice on this topic area only
- →
All PCNE questions
497 questions across all exam domains
- →
Google Professional Cloud Network Engineer study guide
Full concept coverage aligned to exam objectives
- →
PCNE practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related PCNE practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Designing, planning, and prototyping a GCP network practice questions
Practise PCNE questions linked to Designing, planning, and prototyping a GCP network.
Implementing hybrid interconnectivity practice questions
Practise PCNE questions linked to Implementing hybrid interconnectivity.
Configuring network services practice questions
Practise PCNE questions linked to Configuring network services.
Implementing network security practice questions
Practise PCNE questions linked to Implementing network security.
Implementing a Virtual Private Cloud practice questions
Practise PCNE questions linked to Implementing a Virtual Private Cloud.
PCNE fundamentals practice questions
Practise PCNE questions linked to PCNE fundamentals.
PCNE scenario practice questions
Practise PCNE questions linked to PCNE scenario.
PCNE troubleshooting practice questions
Practise PCNE questions linked to PCNE troubleshooting.
Practice this exam
Start a free PCNE practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this PCNE question test?
Implementing a Virtual Private Cloud — This question tests Implementing a Virtual Private Cloud — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Verify that the Cloud Router is advertising the 10.1.0.0/24 subnet to on-premises. — The issue is that the static route for 10.0.0.0/8 with priority 100 may be overwriting the dynamically learned routes for the new subnet. Dynamic routes from Cloud Router have a higher priority (1000) by default, but the static route with lower priority (100) will take precedence. However, since the static route points to the same VPN tunnel, it should still work, but if the static route is for the entire range, it may not be specific enough for the new subnet? Actually, the most specific route wins. The subnet 10.1.0.0/24 is more specific than 10.0.0.0/8, so a dynamic route for 10.1.0.0/24 should be propagated. But since the static route covers 10.0.0.0/8, it does not prevent more specific routes. The problem might be that the Cloud Router is not advertising the new subnet to on-premises, or the on-premises router is not accepting the update, or the BGP session is down. Option A is correct: check if the Cloud Router is advertising the subnet. Option B is correct: check the BGP session status. Option E is correct: check on-premises route tables. Option C is incorrect because changing priority might not help, and Option D is incorrect because you can keep the static route for other subnets.
What should I do if I get this PCNE 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 PCNE subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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 →
Last reviewed: Jun 24, 2026
This PCNE 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 PCNE 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.