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Private IPv4 address spaces
A private network is a network that uses private IP address space, in the Internet addressing architecture, following the standards set by RFC 1918 and RFC 4193. These addresses are commonly used for home, office, and enterprise local area networks (LANs).

These addresses are characterized as private because they are not globally delegated, meaning they are not allocated to any specific organization, and IP packets addressed by them cannot be transmitted onto the public Internet. Anyone may use these addresses without approval from a regional Internet registry (RIR). If such a private network needs to connect to the Internet, it must use either a network address translator (NAT) gateway, or a proxy server.

These are non internet routable adresses :

IP address range number of addresses description CIDR block (subnet mask) host id size
10.0.0.0 - 10.255.255.255 16,777,216 single class A network 10.0.0.0/8 (255.0.0.0) 24 bits
172.16.0.0 - 172.31.255.255 1,048,576 16 contiguous class B network 172.16.0.0/12 (255.240.0.0) 20 bits
192.168.0.0 - 192.168.255.255 65,536 256 contiguous class C network 192.168.0.0/16 (255.255.0.0) 16 bits