Private IP Address Ranges Explained: 10.x, 172.16.x and 192.168.x
Private IP addresses are ranges reserved for internal networks that are not routable on the public internet. This guide covers RFC 1918, why these ranges exist, and how NAT works with them.
ProfitTool Team
Security & Dev
The Three Private Ranges (RFC 1918)
IANA has reserved three IPv4 address ranges for private network use. These addresses are not routable on the public internet — routers at the edge of networks drop packets destined for these addresses.
| Range | CIDR | Available addresses | Typical use |
|---|---|---|---|
| 10.0.0.0 – 10.255.255.255 | 10.0.0.0/8 | 16,777,216 | Large enterprises, cloud VPCs |
| 172.16.0.0 – 172.31.255.255 | 172.16.0.0/12 | 1,048,576 | Medium networks |
| 192.168.0.0 – 192.168.255.255 | 192.168.0.0/16 | 65,536 | Home networks, small offices |
Why Private Ranges Exist
IPv4 has roughly 4.3 billion addresses. In the early 1990s it became clear this would not be enough for every device. RFC 1918 (1996) defined private address space so that organisations could use any of the three ranges internally without registering globally unique addresses. Network Address Translation (NAT) then allows many devices with private IPs to share a single public IP.
How NAT Works
Your home router has one public IP assigned by your ISP. Every device on your home network has a private IP (typically 192.168.x.x). When a device makes an outbound request, the router:
- Replaces the source IP with its public IP
- Records the mapping in a NAT table (private IP + port → public port)
- When the response arrives, reverses the mapping and forwards to the correct device
Special Ranges
| Range | Purpose |
|---|---|
| 127.0.0.0/8 | Loopback (127.0.0.1 = localhost) |
| 169.254.0.0/16 | Link-local / APIPA (no DHCP available) |
| 100.64.0.0/10 | Shared address space for ISP CGN (RFC 6598) |
| 0.0.0.0/8 | "This" network |
Cloud Metadata Endpoint
169.254.169.254 is particularly important in cloud environments — AWS, Azure and GCP expose instance metadata (including credentials) at this address from inside VMs. SSRF vulnerabilities that can reach this IP are critical security issues.
Calculate network ranges with our CIDR / Subnet Calculator.
ProfitTool Team
Security & DevWritten and maintained by the ProfitTool team. Where an article references a ProfitTool utility, the behaviour described is the behaviour of the tool on this site — you can open it and check the output yourself.
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