You need to create a custom VPC with a single subnet. The subnet’s range must be as large as possible. Which range should you use?

In Google Cloud, a Virtual Private Cloud (VPC) subnet is defined by a primary IPv4 range in CIDR notation. The size of the range is determined by the prefix length (the number after the /). A smaller prefix number indicates a larger IP address range. The largest permissible subnet range in Google Cloud VPC is one with a /8 prefix. The range 10.0.0.0/8 provides 2^(32-8) = 16,777,216 addresses, which is the maximum possible for a single subnet, making it the correct choice for the largest possible range.

A. 0.0.0.0/0 is not a valid range for a subnet. This CIDR block represents all IP addresses and is used in routing tables to define a default route, typically to the internet.

C. 172.16.0.0/12 is a valid subnet range, but it is smaller than a /8 range, providing only 2^(32-12) = 1,048,576 addresses.

D. 192.168.0.0/16 is also a valid subnet range, but it is significantly smaller than a /8 range, providing only 2^(32-16) = 65,536 addresses.

1. Google Cloud Documentation - VPC network overview: "Each subnet is associated with a single region and must have at least one primary IPv4 address range." This document establishes the fundamental relationship between VPCs and subnets.

Source: Google Cloud Documentation

"VPC network overview"

Section: "Networks and subnets".

2. Google Cloud Documentation - Subnets: "The prefix length for a primary IPv4 subnet range cannot be smaller than /8." A smaller prefix length number corresponds to a larger IP address block

confirming that /8 is the largest size allowed.

Source: Google Cloud Documentation

"Subnets"

Section: "Subnet ranges"

Subsection: "Valid ranges".

3. Google Cloud SDK Documentation - gcloud compute networks subnets create: The command-line interface documentation explicitly states the constraints on subnet creation: "The prefix length must be between 8 and 29

inclusive." This confirms that /8 is the minimum valid prefix length

which corresponds to the maximum range size.

Source: Google Cloud SDK Documentation

gcloud compute networks subnets create

Argument: --range.

4. IETF RFC 1918 - Address Allocation for Private Internets: This document defines the private IPv4 address spaces

which include 10.0.0.0/8

172.16.0.0/12

and 192.168.0.0/16. While all are valid private ranges

Google Cloud's implementation limits the maximum subnet size to /8.

Source: IETF RFC 1918

Section 3: "Private Address Space".