AWS uses both IPv4 and IPv6 addressing schemes. These addresses determine whether your resources are reachable from the internet or stay private within your VPC.
1️⃣ IPv4 in AWS
| Type | Description | Behavior | Example | Cost |
|---|
| Public IPv4 | Used to connect to the internet. | Assigned automatically to EC2 instances. Released on stop, new one on restart. | 3.120.45.22 | Free |
| Private IPv4 | Used within a private VPC network. | Persistent for the lifetime of the instance. Not reachable from the internet. | 192.168.1.1 | Free |
📝 Note:
If you stop and start your EC2 instance, the public IPv4 changes, but the private IPv4 remains the same.
2️⃣ Elastic IP (EIP)
| Feature | Description |
|---|
| Purpose | Provides a fixed public IPv4 address. |
| Persistence | Remains the same even if the instance is stopped and started. |
| Use Case | Needed when a static IP is required (e.g., DNS mapping, firewall rules). |
| Pricing | Charged if not actively associated with a running instance. |
3️⃣ IPv6 in AWS
| Property | Details |
|---|
| Protocol | IPv6 (Internet Protocol version 6) |
| Address Space | 3.4 × 10³⁸ addresses (virtually unlimited) |
| Format Example | 2600:1f18:abcd:1234::1 |
| Accessibility | All IPv6 addresses are public (no private ranges) |
| Cost | Free in AWS |
💡 Tip:
Use IPv6 to expose your applications publicly without incurring IPv4 costs.
🧩 Summary
| Concept | IPv4 | IPv6 |
|---|
| Address Type | Public & Private | Public only |
| Cost | $0.005/hour(Elastic) | Free |
| Persistence | Public IP changes on restart | Permanent |
| Use Case | Legacy & compatibility | Modern, scalable networking |