- A
Two tunnels: both tunnels from the same on-premises interface to two different Cloud Router instances
Why wrong: Sharing the same interface creates a single point of failure.
- B
Two tunnels: each tunnel from a separate on-premises interface to the same Cloud Router instance
Why wrong: All tunnels terminate on one Cloud Router, single point of failure.
- C
Four tunnels: two tunnels from each on-premises interface to the same Cloud Router instance
Why wrong: Two tunnels to the same Cloud Router instance still has a single point of failure at the Cloud Router level.
- D
Four tunnels: one tunnel from each on-premises interface to each Cloud Router instance, totaling four BGP sessions
This provides full device and path redundancy suitable for 99.99% availability.
Quick Answer
The correct configuration is four tunnels: one tunnel from each on-premises interface to each Cloud Router instance, totaling four BGP sessions. This meets the 99.99% availability goal because HA VPN design for high availability requires full mesh redundancy between the two on-premises interfaces and the two Cloud Router instances, ensuring that any single failure—whether an on-premises interface, a Cloud Router, or a tunnel—still leaves at least one active path for traffic. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding that HA VPN’s SLA is achieved only when both Cloud Routers and both on-premises interfaces are fully utilized with distinct BGP sessions; a common trap is assuming two tunnels (one per Cloud Router) are sufficient, but that leaves a single point of failure on the on-premises side. Remember the memory tip: “two times two equals four tunnels” — each on-premises interface must talk to each Cloud Router to eliminate all single points of failure.
PCNE Implementing hybrid interconnectivity Practice Question
This PCNE practice question tests your understanding of implementing hybrid interconnectivity. 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 is designing an HA VPN to connect their on-premises data center to Google Cloud VPC. The on-premises router supports two independent interfaces with public IPs. They want to achieve 99.99% availability for the VPN connection, understanding that HA VPN uses two tunnels and two Cloud Router instances. Which configuration meets this goal?
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
Four tunnels: one tunnel from each on-premises interface to each Cloud Router instance, totaling four BGP sessions
Option D is correct because HA VPN requires at least two Cloud Router instances and two tunnels from each on-premises interface to each Cloud Router instance to achieve 99.99% availability. This configuration creates four BGP sessions, ensuring that if one on-premises interface, one Cloud Router, or one tunnel fails, traffic can still flow through the remaining paths. The design leverages both redundancy of interfaces and redundancy of Cloud Routers to meet the high availability SLA.
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.
- ✗
Two tunnels: both tunnels from the same on-premises interface to two different Cloud Router instances
Why it's wrong here
Sharing the same interface creates a single point of failure.
- ✗
Two tunnels: each tunnel from a separate on-premises interface to the same Cloud Router instance
Why it's wrong here
All tunnels terminate on one Cloud Router, single point of failure.
- ✗
Four tunnels: two tunnels from each on-premises interface to the same Cloud Router instance
Why it's wrong here
Two tunnels to the same Cloud Router instance still has a single point of failure at the Cloud Router level.
- ✓
Four tunnels: one tunnel from each on-premises interface to each Cloud Router instance, totaling four BGP sessions
Why this is correct
This provides full device and path redundancy suitable for 99.99% availability.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think two tunnels (one per interface) to the same Cloud Router is sufficient, but they overlook that the Cloud Router itself is a single point of failure, and HA VPN requires redundancy at both the on-premises and Cloud Router layers to achieve 99.99% availability.
Detailed technical explanation
How to think about this question
HA VPN in Google Cloud uses two Cloud Router instances in different zones for regional redundancy, and each tunnel is a separate IPsec tunnel with its own BGP session. The four-tunnel design (two tunnels per on-premises interface, each to a different Cloud Router) ensures that any single failure—whether on-premises interface, Cloud Router, or tunnel—still leaves at least one active BGP session. This design aligns with Google's recommended HA VPN topology for 99.99% availability, which requires at least two Cloud Routers and two tunnels per interface.
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.
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FAQ
Questions learners often ask
What does this PCNE question test?
Implementing hybrid interconnectivity — This question tests Implementing hybrid interconnectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Four tunnels: one tunnel from each on-premises interface to each Cloud Router instance, totaling four BGP sessions — Option D is correct because HA VPN requires at least two Cloud Router instances and two tunnels from each on-premises interface to each Cloud Router instance to achieve 99.99% availability. This configuration creates four BGP sessions, ensuring that if one on-premises interface, one Cloud Router, or one tunnel fails, traffic can still flow through the remaining paths. The design leverages both redundancy of interfaces and redundancy of Cloud Routers to meet the high availability SLA.
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.
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 →
Same concept, more angles
1 more ways this is tested on PCNE
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company wants to connect its on-premises data center to Google Cloud. They have a single VPN appliance on-premises and need high availability for the connection. Which architecture provides the most cost-effective high availability solution?
easy- ✓ A.Deploy Cloud HA VPN with two interfaces, each with its own external IP address, and configure two tunnels to the on-premises VPN appliance.
- B.Use a single Cloud Classic VPN tunnel with a static route.
- C.Deploy two Cloud Classic VPN gateways in the same region, each with one tunnel to the on-premises VPN appliance.
- D.Deploy Cloud HA VPN with one interface and one external IP address, and configure a single tunnel to the on-premises appliance.
Why A: Option D is correct because Cloud HA VPN uses two external IP addresses per tunnel and automatically provides high availability by using two VPN gateways in different regions. Option A is incorrect because using two Cloud VPN gateways in the same region does not protect against zonal failure. Option B is incorrect because a single Classic VPN tunnel is not highly available. Option C is incorrect because HA VPN with a single IP per tunnel is not supported; HA VPN requires at least two IPs.
Last reviewed: Jun 25, 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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