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Difficulty: HardPlanning Virtual Private Cloud (VPC) Networks and Subnets

A network engineering lead at a financial institution is designing a multi-tier enterprise architecture in Google Cloud. The infrastructure requires dedicated Virtual Private Cloud (VPC) subnets across multiple regions for database clusters, web microservices, and internal administrative services. To enforce strict administrative segregation and prevent cross-team network provisioning errors, the security governance team dictates that IP address allocations must be explicitly controlled per subnet without automatic default subnet creation across all GCP regions. Furthermore, the architecture must support future IP space expansion without downtime, while maintaining isolation from legacy on-premises RFC 1918 addresses. Which VPC network design approach best satisfies these requirements?

  1. Create a custom-mode VPC network, explicitly defining subnets with tailored primary CIDR blocks in required regions, and leave auto-create subnets disabled.Answer
  2. B
    Create an auto-mode VPC network, then convert it to custom mode immediately after creation to clean up unwanted regional subnets.
  3. C
    Create an auto-mode VPC network and modify the firewall rules to block traffic to unapproved regional default subnets.
  4. D
    Create a legacy VPC network with a single global IP address space shared across all regions without using individual subnets.

Answer

Create a custom-mode VPC network with explicitly defined regional subnets and customized primary CIDR ranges.
Custom-mode VPC networks give full control over subnet creation. No subnets are created automatically, preventing unexpected IP range collisions with existing on-premises networks and enabling strict regional governance and precise IP planning.

Step-by-Step Solution

1
Analyze enterprise requirements
Identified requirements for explicit IP address management, regional subnet control, prevention of automatic region-wide subnet creation, and non-overlapping IP space with on-premises networks.
Enterprise hybrid environments require custom CIDR range selection to avoid overlapping with existing corporate IP space.
2
Evaluate GCP VPC network creation modes
Auto-mode automatically populates a predefined /20 subnet in every GCP region, whereas custom-mode creates zero subnets initially, giving complete control over subnet creation, regional placement, and CIDR sizing.
Custom-mode VPCs ensure compliance with strict organizational IP governance and facilitate seamless subnet expansion.
3
Select optimal architecture
Provisioning a custom-mode VPC network fulfills all administrative isolation, zero default subnet, and IP planning constraints.
Custom mode is the recommended best practice for enterprise production workloads.

Key Concept

VPC Network Modes and Subnet IP Planning
Estimated Time:2m 0s
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Topics

Planning Virtual Private Cloud (VPC) Networks and Subnets

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