Google ACE Planning and Configuring a Cloud Solution Practice Question
An engineer is tasked with creating a new VPC network for a production environment. The company requires the VPC to support multiple regions and allow custom IP address ranges for each subnet. Which VPC network mode should the engineer use?
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
✓
Custom mode VPC
Custom mode VPC allows full control over subnets, including custom IP ranges per region. Auto mode creates subnets in each region with predefined IP ranges, which may not meet production requirements. Shared VPC is for sharing across projects, not for a single project's network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Shared VPC
Why it's wrong here
Shared VPC is a cross-project networking model where a host project owns the subnets and service projects consume them; it is not a VPC network 'mode' that selects IP addressing. Even in Shared VPC, each subnet's CIDR must be chosen within the host project using either custom or auto mode, so it does not itself define or enable custom IP ranges. For an engineer creating a new VPC, Shared VPC is irrelevant because the question is about subnet IP range control, not resource sharing.
- ✓
Custom mode VPC
Why this is correct
Custom mode VPC is the correct choice because it begins with no subnets and lets the engineer explicitly define each subnet's IP CIDR range and region. This provides full control over the address space, including private or publicly routable blocks, to avoid conflicts and meet design requirements. For a task that requires setting custom subnet IP ranges per region, this mode is the only way to do so natively.
- ✗
Auto mode VPC
Why it's wrong here
Auto mode VPC automatically creates one /20 subnet in every Google Cloud region from a fixed 10.128.0.0/9 block, and those automatically generated subnets cannot have their IP ranges changed. While you can add additional subnets in an auto mode network, the key requirement of fully customizing per-region CIDRs is defeated because the pre-created subnets are fixed. This mode is primarily for quick experimentation, not for controlled IP design.
- ✗
Legacy mode VPC
Why it's wrong here
Legacy mode VPC is an obsolete network type from GCP's early days that uses a single flat IP range with no regional subnets at all. It does not support the subnet-based architecture needed to assign different CIDR ranges per region, and Google has deprecated it, so it cannot be used for new VPC designs. Therefore it fails both on functionality and on cloud best practices.
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GCP Projects, Folders, and Organizations
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
Key term
IP address
An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ACE 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 ACE exam.