IPv4 Private Address Space

Nonroutable / Non-Routable / non-routable otherwise known as Private Network Address Space.

Non-routable address space allows for nodes to communicate with each other on same network and will not conflict to other network addressing on the Internet. IP packets originating from or addressed to a private IP address cannot be routed through the public Internet.

Both the IPv4 and the IPv6 specifications define private IP address ranges. These addresses are commonly used for local area networks (LANs) in residential, office, and enterprise environments. Private network addresses are not allocated to any specific organization. Private IP address spaces were originally defined to assist in delaying IPv4 address exhaustion.

According to standards set forth in Internet Engineering Task Force (IETF) document RFC-1918, the following IPv4 address ranges are reserved by the IANA for private internets, and are not publicly routable on the global internet:

• 10.0.0.0/8 IP addresses: 10.0.0.0 – 10.255.255.255
• 172.16.0.0/12 IP addresses: 172.16.0.0 – 172.31.255.255
• 192.168.0.0/16 IP addresses: 192.168.0.0 – 192.168.255.255

Only a portion of the “172” and the “192” address ranges are designated for private use. The remaining addresses are considered “public,” and thus are routable on the global Internet.