Internal IP address ranges, also known as private IP addresses, are blocks of IP addresses specifically reserved for use within private networks. These networks include home networks, small businesses, and large corporate environments. They are defined by RFC 1918 and are not routable on the public internet, meaning they cannot be directly accessed from outside your local network.
Using private IP addresses allows organizations to number their internal hosts without needing to obtain unique global IP addresses for every device. Instead, devices on the private network communicate with the internet using a mechanism like Network Address Translation (NAT), which maps multiple private IP addresses to one or a few public IP addresses.
According to RFC 1918, there are three primary blocks of IP addresses designated for private networks:
Reserved Private IPv4 Address Ranges
The following table outlines the standard private IPv4 address ranges:
| RFC 1918 Name | IP Address Range | Largest CIDR Block (Subnet Mask) |
|---|---|---|
| 24-bit block | 10.0.0.0 – 10.255.255.255 | 10.0.0.0/8 (255.0.0.0) |
| 20-bit block | 172.16.0.0 – 172.31.255.255 | 172.16.0.0/12 (255.240.0.0) |
| 16-bit block | 192.168.0.0 – 192.168.255.255 | 192.168.0.0/16 (255.255.0.0) |
These ranges are widely used in various network setups:
- 10.0.0.0/8: Often used in larger corporate networks due to the vast number of available addresses.
- 172.16.0.0/12: Provides a flexible range suitable for medium-sized networks.
- 192.168.0.0/16: Commonly used in home and small office networks (e.g., your router likely assigns addresses in the 192.168.1.x or 192.168.0.x range).
These ranges ensure that there is no conflict with publicly assigned IP addresses, providing a robust and scalable method for internal network addressing.
