1The Importance of CIDR Planning
One of the most common and painful mistakes in cloud architecture is choosing overlapping CIDR blocks (e.g., using 10.0.0.0/16 for every VPC). If your company acquires another business or needs to establish VPC Peering with another internal department, overlapping CIDR blocks make direct peering impossible. Network architects must establish an IPAM (IP Address Manager) strategy from day one to ensure unique, non-overlapping IP ranges across the entire organization.
2Default vs Custom VPC Architecture
While the Default VPC is convenient for quick experimentation, it is highly discouraged for production workloads. The Default VPC places all resources into public subnets with automatic public IP assignment. Enterprise security best practices mandate creating custom VPCs where the vast majority of workloads (databases, application servers) reside in isolated private subnets, with only load balancers or bastion hosts exposed to the public internet.
