- A
Cloud NAT must be configured for the backend subnet.
Why wrong: Cloud NAT is used for outbound internet access from private instances, but it is not required for a public load balancer to route traffic to backend instances. The load balancer uses internal routing.
- B
The backend subnet must have a default route to the internet.
Why wrong: A default route to the internet is not needed. The public load balancer can reach private instances through the VPC internal IP addresses without a default route.
- C
Private Google Access must be enabled on the backend subnet.
Why wrong: Private Google Access allows instances without external IPs to access Google APIs and services, but it is not required for load balancer traffic.
- D
No additional configuration is required beyond creating the subnet.
As long as the backend instances are in the same VPC as the load balancer, they can receive traffic from the load balancer without any additional configuration like NAT or Private Google Access.
Public Load Balancer to Private Backend
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 wants to deploy a web application with a public-facing load balancer and a private backend. The backend instances must not have external IPs. Which statement about the VPC configuration is correct?
Quick Answer
The correct answer is that no additional configuration is required beyond creating the subnet. This is because a public load balancer in Google Cloud uses internal VPC routing to forward traffic to backend instances, even when those instances lack external IPs. The load balancer’s envoy proxies reside within the VPC and communicate with backends over private IP addresses, so no NAT gateway, Private Google Access, or default route is needed. On the Google Professional Cloud Network Engineer exam, this concept tests your understanding of how load balancers decouple frontend and backend networking—a common trap is assuming private backends need outbound internet access or special routes. Remember: the load balancer is the endpoint; the backend only needs to be reachable within the VPC. A useful memory tip is “LB is the bridge, not the boat”—the load balancer handles public ingress, while backends stay private and require no extra configuration.
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
No additional configuration is required beyond creating the subnet.
Option D is correct because instances without external IPs can still receive traffic from a public load balancer. No additional configuration such as NAT or Private Google Access is needed. Option A is incorrect because Cloud NAT provides outbound internet access, not required for load balancer traffic. Option B is incorrect because the backend subnet does not need a default route to the internet; the load balancer uses internal routing. Option C is incorrect because Private Google Access is for accessing Google APIs, not for load balancer traffic.
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.
- ✗
Cloud NAT must be configured for the backend subnet.
Why it's wrong here
Cloud NAT is used for outbound internet access from private instances, but it is not required for a public load balancer to route traffic to backend instances. The load balancer uses internal routing.
- ✗
The backend subnet must have a default route to the internet.
Why it's wrong here
A default route to the internet is not needed. The public load balancer can reach private instances through the VPC internal IP addresses without a default route.
- ✗
Private Google Access must be enabled on the backend subnet.
Why it's wrong here
Private Google Access allows instances without external IPs to access Google APIs and services, but it is not required for load balancer traffic.
- ✓
No additional configuration is required beyond creating the subnet.
Why this is correct
As long as the backend instances are in the same VPC as the load balancer, they can receive traffic from the load balancer without any additional configuration like NAT or Private Google Access.
Related concept
CIDR notation defines the prefix length.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Visual reference
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
1,000 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.
Configuring Network Services practice questions
Practise PCNE questions linked to Configuring Network Services.
Implementing Hybrid Interconnectivity practice questions
Practise PCNE questions linked to Implementing Hybrid Interconnectivity.
Managing, Monitoring, and Optimising Network Operations practice questions
Practise PCNE questions linked to Managing, Monitoring, and Optimising Network Operations.
Designing, Planning, and Prototyping a GCP Network practice questions
Practise PCNE questions linked to Designing, Planning, and Prototyping a GCP Network.
Implementing VPC Instances practice questions
Practise PCNE questions linked to Implementing VPC Instances.
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: No additional configuration is required beyond creating the subnet. — Option D is correct because instances without external IPs can still receive traffic from a public load balancer. No additional configuration such as NAT or Private Google Access is needed. Option A is incorrect because Cloud NAT provides outbound internet access, not required for load balancer traffic. Option B is incorrect because the backend subnet does not need a default route to the internet; the load balancer uses internal routing. Option C is incorrect because Private Google Access is for accessing Google APIs, not for load balancer traffic.
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 →
Keep practising
More PCNE practice questions
- An organization is migrating to Google Cloud and requires connectivity between their on-premises network and VPC. They p…
- A company is migrating on-premises DNS to Google Cloud. They have a hybrid network using Cloud VPN and want to resolve o…
- A network engineer is configuring a Cloud Router for BGP peering with an on-premises router over a VPN tunnel. The on-pr…
- A company uses Cloud NAT to allow private instances to reach the internet. They notice that egress traffic from Compute…
- You are setting up Partner Interconnect with a service provider that offers both Layer 2 and Layer 3 options. Your on-pr…
- Match each VPC networking concept to its definition.
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.