What Is a Private IP Address?
A private IP address is an IP address from a range reserved for use within private networks - Your home, office, or data center LAN. These addresses are defined by RFC 1918 and are not routable on the public internet. Devices with private IPs communicate with the internet through Network Address Translation (NAT) performed by your router.
RFC 1918 Private IP Ranges
| Range | CIDR Notation | Total Addresses | Common Use |
|---|---|---|---|
| 10.0.0.0 – 10.255.255.255 | 10.0.0.0/8 | 16,777,216 | Large enterprise networks, VPNs |
| 172.16.0.0 – 172.31.255.255 | 172.16.0.0/12 | 1,048,576 | Medium-sized corporate networks |
| 192.168.0.0 – 192.168.255.255 | 192.168.0.0/16 | 65,536 | Home routers (192.168.0.x / 192.168.1.x) |
| 169.254.0.0 – 169.254.255.255 | 169.254.0.0/16 | 65,536 | APIPA - Assigned when DHCP fails (not RFC 1918) |
| 127.0.0.0 – 127.255.255.255 | 127.0.0.0/8 | 16,777,216 | Loopback - Local device only (not RFC 1918) |
How NAT Bridges Private and Public Addresses
Your router holds one public IP address (assigned by your ISP) and assigns private IPs to every device on your network. When a device sends traffic to the internet, the router replaces the private source IP with its public IP, keeps a translation table of the mapping, and reverses the substitution when the response arrives. This is why multiple devices can share a single public IP.
Finding Your Private IP Address
- Windows: open Command Prompt and run
ipconfig- Look for "IPv4 Address" under your active adapter. - macOS / Linux: open Terminal and run
ip addrorifconfig- Look for "inet" entries excluding 127.0.0.1. - Android: Settings → Wi-Fi → tap your network → Advanced - Look for IP address.
- iPhone / iPad: Settings → Wi-Fi → tap the (i) next to your network - Look for IP Address.
- Your router's admin panel (usually at 192.168.1.1 or 192.168.0.1) lists all connected devices and their private IPs.