A private network is a computer network that uses private IP addresses for communication within an organization, home, or business. These IP addresses are reserved for internal use only and cannot be accessed directly from the public Internet. In IPv4, around 18 million IP addresses are reserved specifically for private networks.
When data packets containing private IP addresses are sent to the Internet, public routers do not forward them because these addresses are not globally routable. Therefore, devices using private IP addresses cannot communicate directly with devices on the Internet. To access the Internet, a private network must use Network Address Translation (NAT), which is usually performed by a router or gateway. NAT converts private IP addresses into a public IP address before transmitting data over the Internet.
Reserved Private IPv4 Address Ranges
| Private Network | CIDR Block | Address Range | Number of IP Addresses | Classful Description |
|---|---|---|---|---|
| 24-bit Block | 10.0.0.0/8 | 10.0.0.0 – 10.255.255.255 | 16,777,216 | Single Class A Network |
| 20-bit Block | 172.16.0.0/12 | 172.16.0.0 – 172.31.255.255 | 1,048,576 | Range of 16 Class B Networks |
| 16-bit Block | 192.168.0.0/16 | 192.168.0.0 – 192.168.255.255 | 65,536 | Range of 256 Class C Networks |
Sometimes an organization has multiple private networks located at different places, such as branch offices in different cities. Since private IP addresses cannot be routed over the public Internet, these networks cannot communicate directly with each other.
To connect such private networks securely, organizations use a Virtual Private Network (VPN) or another type of IP tunnel. A VPN creates a secure connection over the Internet by encapsulating the original data packets, including their private IP addresses, inside new packets that can travel across the public network. In most cases, these packets are also encrypted, ensuring that the transmitted data remains secure and protected from unauthorized access.