ℹ️ What are Subnets?
Subnets are segments of a VPC’s IP address range where you can place groups of isolated resources. They allow you to organize your network architecture into public subnets (internet-accessible) and private subnets (internal only) across multiple Availability Zones for high availability.
Public Subnet 1
10.10.1.0/24
(providing 256 IP addresses)10.10.2.0/24
10.10.3.0/24
10.10.4.0/24
💡 Pro Tip
AWS displays both Availability Zone names and Availability Zone IDs in the console. AWS randomly maps AZ names (like ap-southeast-1a) to physical AZ IDs (like apse1-az2) across different AWS accounts to distribute workloads evenly. When designing multi-AZ architectures across accounts, always reference AZ IDs rather than AZ names for consistency.
ℹ️ What Makes a Subnet “Public”?
A subnet becomes “public” when it has a route to an Internet Gateway and instances within it can receive public IP addresses. By default, newly created subnets do not automatically assign public IP addresses to instances launched within them.
💡 Pro Tip
The distinction between public and private subnets is determined by routing configuration and IP address assignment, not by any inherent subnet property. Both use the same subnet resource type in AWS.
⚠️ Important Consideration
While we’ve enabled auto-assign public IP addresses for our public subnets, instances in these subnets will not have internet connectivity until we create and attach an Internet Gateway and configure the appropriate route tables in subsequent steps.