- A
Use NAT to map multiple private IPs to one public IP.
Why wrong: NAT is for address translation, not for creating redundant VPN endpoints.
- B
Use Classic VPN with a single tunnel.
Why wrong: Classic VPN is not highly available and does not support dynamic routing.
- C
Use HA VPN with two on-premises public IPs and two tunnels.
HA VPN provides redundancy by supporting active-active or active-passive with separate endpoints.
- D
Use HA VPN with the same public IP for both tunnels.
Why wrong: Using the same IP defeats the purpose of redundancy; a single point of failure remains.
Question 584 of 1,000
hardMultiple ChoiceObjective-mapped
HA VPN with Limited On-Premises Public IPs — Two Tunnels Required | Google Professional Cloud Network Engineer Explained
This PCNE practice question tests your understanding of pcne exam topics. 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 with limited public IP addresses on-premises needs to connect to Google Cloud using Cloud VPN. They require high availability. Which solution should they implement?
Quick Answer
The correct answer is to deploy HA VPN using two on-premises public IPs and two tunnels. This configuration ensures high availability by establishing two separate IPSec tunnels, each terminating on a distinct on-premises VPN gateway with its own unique public IP address. If one on-premises public IP or tunnel fails, traffic automatically fails over to the other tunnel, eliminating any single point of failure at the on-premises edge. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding that HA VPN requires two unique public IPs on-premises to achieve active-active failover, a common trap where candidates mistakenly reuse the same public IP for both tunnels, which creates a single point of failure and violates the high-availability requirement. Classic VPN is also a distractor because it only supports active-passive failover. Memory tip: think "two tunnels, two IPs, two gateways" — if any one of those is missing, you lose high availability.
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
✓
Use HA VPN with two on-premises public IPs and two tunnels.
HA VPN provides high availability by using two tunnels, each terminating on a separate on-premises VPN gateway with a unique public IP address. This ensures that if one on-premises public IP or tunnel fails, traffic can still flow through the other tunnel, meeting the high-availability requirement. Classic VPN (option B) does not support active-active failover, and using the same public IP for both tunnels (option D) creates a single point of failure at the on-premises side.
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.
- ✗
Use NAT to map multiple private IPs to one public IP.
- ✗
Use Classic VPN with a single tunnel.
Why it's wrong here
Classic VPN is not highly available and does not support dynamic routing.
- ✓
Use HA VPN with two on-premises public IPs and two tunnels.
Why this is correct
HA VPN provides redundancy by supporting active-active or active-passive with separate endpoints.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use HA VPN with the same public IP for both tunnels.
Why it's wrong here
Using the same IP defeats the purpose of redundancy; a single point of failure remains.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that HA VPN can use the same on-premises public IP for both tunnels, but in reality, each tunnel must terminate on a separate on-premises device or interface with a unique public IP to achieve true high availability.
Detailed technical explanation
How to think about this question
HA VPN uses two IPsec tunnels (each with its own BGP session) to provide active-active or active-passive failover. Under the hood, each tunnel is associated with a separate Cloud VPN gateway interface and a separate on-premises VPN device, requiring two unique public IPs on-premises. In a real-world scenario, if the on-premises ISP link for one public IP goes down, BGP withdraws the routes for that tunnel, and traffic automatically shifts to the remaining tunnel, ensuring continuous connectivity.
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.
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
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.
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FAQ
Questions learners often ask
What does this PCNE question test?
Read the scenario before looking for a memorised answer.
What is the correct answer to this question?
The correct answer is: Use HA VPN with two on-premises public IPs and two tunnels. — HA VPN provides high availability by using two tunnels, each terminating on a separate on-premises VPN gateway with a unique public IP address. This ensures that if one on-premises public IP or tunnel fails, traffic can still flow through the other tunnel, meeting the high-availability requirement. Classic VPN (option B) does not support active-active failover, and using the same public IP for both tunnels (option D) creates a single point of failure at the on-premises side.
What should I do if I get this PCNE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 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.
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