The Difference Between Private and Public IP Addressesby Skip Shelton
Internet Protocol addresses, or IP addresses, route Internet traffic between devices. IP address designation identifies specific computers or devices actively connecting to the Internet or network. Addresses range from 0 to 255 in four groupings with each group separated by a period, such as 192.168.100.100. Specific IP address ranges designate private networks.
Advantages of Private Address Reservation
Private networks prevent depletion of publicly-available IP addresses. Private address ranges enable reuse of IP address ranges of network devices not directly connecting to the Internet.
Private Network Uses
Private networks connect devices to a local network without being directly visible to the Internet. Public IP address-equipped routers provide Internet connectivity for most private networks. Private networks limit intrusion by Internet connections. Internet connectivity is not required on private networks. While private networks have Internet visibility and can access the Internet -- public networks cannot access the private network.
Private IP Address Ranges
Three ranges of IP addresses are designated for private use: 10.0.0.1 to 10.255.255.254, the range 172.16.0.1 to 172.31.255.254 and the range 192.168.0.1 to 192.168.255.254.
Public IP Addresses
All public IP addresses must be reserved before use. If devices connect to the Internet using a public IP address not reserved, the address is considered "illegal" and will not function.
Domain Name Registry
Domain Name Registry services further expand the available addressable space on the World Wide Web by registering a qualified domain name or website, such as the one found for the Internal Revenue Service to specific IP addresses. A single registered IP address references a single computer hosting one or more domain names or websites. This method expands the possible connected websites and simplifies browsing on the Internet.
According to Microsoft, the addresses on the Internet designated for public use are guaranteed to be unique to the Internet and globally available to any Internet-connected devices. Publicly available IP addresses are filterable through the use of IP address filters. Many countries, businesses and educational institutions around the globe use IP filters to prevent unauthorized access to certain portions of the Internet. Many Internet content filters available to home users utilize this method.