The correct choice is to place both instances in the same VPC using internal IP addresses, as this configuration achieves sub-millisecond latency between instances in different zones within the same region. This works because traffic between internal IPs stays entirely on Google’s private backbone, bypassing external gateways and internet hops; the packets are forwarded at the hypervisor level with no encapsulation, ensuring the lowest possible latency. On the Google Professional Cloud Network Engineer exam, this scenario tests your understanding of VPC routing fundamentals versus external IP or multi-VPC peering options—a common trap is assuming that using external IPs or VPC peering across different VPCs is faster, but those introduce additional network hops or gateway processing. Remember the memory tip: “Same VPC, internal IPs—no hops, no stops.”
PCNE Implementing a Virtual Private Cloud Practice Question
This PCNE practice question tests your understanding of implementing a virtual private cloud. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 a network for a critical application that requires sub-millisecond latency between two Compute Engine instances. The instances are located in different zones within the same region. Which VPC configuration will provide the lowest latency?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Place both instances in the same VPC, using internal IP addresses.
Option C is correct because placing both Compute Engine instances in the same VPC and using internal IP addresses ensures traffic stays within Google's private network backbone, bypassing any external gateways or internet hops. This configuration leverages Google's internal routing with sub-millisecond latency between zones in the same region, as traffic is forwarded at the hypervisor level without encapsulation or additional network hops.
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 VPC Network Peering between two different VPCs.
Why it's wrong here
Peering adds a slight overhead; same VPC is better.
✗
Place instances in different VPCs and use a VPN between them.
Place both instances in the same VPC, using internal IP addresses.
Why this is correct
Internal IPs stay within Google's network, providing lowest latency.
Related concept
Read the scenario before looking for a memorised answer.
✗
Assign external IP addresses to both instances and communicate over the internet.
Why it's wrong here
External IPs traverse the internet gateway, increasing latency.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that VPC Network Peering provides equivalent latency to a single VPC, but the trap here is that peering adds a logical routing boundary and potential latency overhead, making a single VPC with internal IPs the only option for guaranteed sub-millisecond performance.
Detailed technical explanation
How to think about this question
Within a single VPC, Google Cloud uses Andromeda, its software-defined networking stack, to forward traffic between instances in different zones using internal IP addresses. This traffic stays on Google's Jupiter data center fabric, which provides consistent sub-millisecond latency (typically 0.5–1 ms) across zones in the same region. In contrast, VPC Network Peering relies on separate VPC routing tables and may introduce additional latency due to the peering link, especially under high throughput.
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.
Implementing a Virtual Private Cloud — This question tests Implementing a Virtual Private Cloud — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Place both instances in the same VPC, using internal IP addresses. — Option C is correct because placing both Compute Engine instances in the same VPC and using internal IP addresses ensures traffic stays within Google's private network backbone, bypassing any external gateways or internet hops. This configuration leverages Google's internal routing with sub-millisecond latency between zones in the same region, as traffic is forwarded at the hypervisor level without encapsulation or additional network hops.
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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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
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