Understanding the difference between public and private IP addresses is fundamental to network design. Each type serves a specific purpose in internet connectivity.
Public IP Addresses
Public IP addresses are globally unique and directly routable on the internet. They are assigned by Regional Internet Registries (RIRs) and are required for any device that needs to be directly accessible from the internet.
Web servers, email servers, VPN endpoints, and API gateways all require public IP addresses to receive incoming connections.
Private IP Addresses
Private IP addresses are reserved for use within local networks and cannot be routed on the public internet. They can be reused in any private network.
10.0.0.0/8
16.7 million addresses
172.16.0.0/12
1 million addresses
192.168.0.0/16
65,536 addresses
Key Differences
Understanding when to use each type is essential for network architecture.
| Aspect | Public IP | Private IP |
|---|---|---|
| Scope | Global, internet-wide | Local network only |
| Uniqueness | Globally unique | Can be reused |
| Cost | Requires lease/purchase | Free to use |
| Internet Access | Direct | Via NAT |
When Do You Need Public IPs?
You need public IP addresses when hosting public-facing services.
- Web servers and websites
- Email servers (SMTP/IMAP)
- VPN gateways and endpoints
- Game servers and real-time applications
- API endpoints and SaaS applications