🏢 What Is a Subnet in AWS?
A subnet in AWS is like a physical building within a specific location (called a region).
For example, take the Ireland region (eu-west-1). In Dublin, AWS may have 3 separate buildings — each one is a subnet, located in a different Availability Zone (AZ).
📌 Why Subnets Exist
This setup is all about High Availability (HA). If one building (subnet) has an issue (like power loss), the others can still operate. This helps keep your applications running smoothly.
🖥️ Hosting a Server in a Subnet
When you launch an EC2 instance (a virtual server), you choose which Availability Zone (and thus which subnet) it will run in.
Example:
- If you launch it in
eu-west-1a, your server runs in Subnet A — a specific physical data center building in the Ireland region.
🔁 Summary
- Subnet = A part of a VPC in one Availability Zone (a physical data center).
- Availability Zones = Separate buildings or locations in the same region.
- Subnets help with fault tolerance and redundancy.