AWS VPC Networking Explained: CIDR, Subnets, Route Tables, and Gateways

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A technical guide published on DEV Community breaks down the core components of AWS Virtual Private Cloud (VPC) networking, explaining not just what each element is but why it is designed that way. The article covers CIDR block sizing, noting that AWS reserves five IP addresses per subnet and recommending a /16 block for the VPC itself to avoid costly renumbering later. It outlines a practical three-availability-zone production layout using 10.0.0.0/16, with distinct subnet tiers for public-facing resources, application workloads, and data services, emphasizing that larger /20 blocks are needed for app tiers due to EKS pod IP consumption. The guide clarifies that a subnet's public or private designation is determined entirely by its associated route table, not any inherent subnet property. It also details how Internet Gateways and NAT Gateways function, and stresses that route table associations must be explicitly configured in Terraform for routing to take effect.

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