Defining a range of IP addresses is a critical initial step in creating a custom Virtual Private Cloud (VPC) because the range of IP addresses determines the available address space that your VPC will use. This range is crucial for network segmentation, allowing you to assign addresses to resources like virtual machines, load balancers, and other network components. When you define the IP range correctly, you ensure that there are enough addresses for your expected infrastructure needs while avoiding overlaps with other networks.
Additionally, choosing a private IP address range that aligns with the requirements of your applications and avoids conflicts in wider network configurations is essential. This step sets the foundation for routing, firewall configurations, and general network management within your VPC.
The other options may be pertinent to the overall project management framework or the broader context of using Google Cloud, but they do not directly pertain to the technical process of designing and launching a custom VPC.