Note that 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.

In Internet networking, a private network is a computer network that uses a private address space of IP addresses. Both the IPv4 and the IPv6 specifications define private IP address ranges. Private network addresses are not allocated to any specific organization.

Summarizing the differences between private and public IP addresses

Technical explanation. IPv6 addresses are each 128 bits long. Because each digit in an IPv6 address can have 16 different values (from 0 to 15), each digit represents the overall value of 4 bits (one nibble), with 32 digits total. As with IPv4, CIDR notation describes ranges in terms of a common prefix of bits.

Private Address Ranges

• Class A: 10.0. 0.0 to 10.255. 255.255.
• Class B: 172.16. 0.0 to 172.31. 255.255.
• Class C: 192.168. 0.0 to 192.168. 255.255.

The prefix 2001:db8::/32 is a special IPv6 prefix that is used specifically for documentation examples. You can also specify a subnet prefix, which defines the internal topology of the network to a router. The example IPv6 address has the following subnet prefix. The subnet prefix always contains 64 bits.

Automatic Private IP Addressing (APIPA) is a feature of Windows-based operating systems (included in Windows 98, ME, 2000, and XP) that enables a computer to automatically assign itself an IP address when there is no Dynamic Host Configuration Protocol (DHCP) server available to perform that function.

An IPv6 address is represented as eight groups of four hexadecimal digits, each group representing 16 bits The groups are separated by colons (:). An example of an IPv6 address is: 2001:0db8:85a3:0000:0000:8a2e:0370:7334. The standards provide flexibility in the representation of IPv6 addresses.

65,536
IPv6 Relative Network Sizes

The class A network number 127 is assigned the “loopback” function, that is, a datagram sent by a higher level protocol to a network 127 address should loop back inside the host. No datagram “sent” to a network 127 address should ever appear on any network anywhere.

Address Allocation for Private Internets
Request for Comment 1918 (RFC 1918), “Address Allocation for Private Internets,” is the Internet Engineering Task Force (IETF) memorandum on methods of assigning of private IP addresses on TCP/IP networks. A private network can use a single public IP address.

Description. This standard (RFC) defines the addressing architecture of the IP Version 6 (IPv6) protocol. It includes the IPv6 addressing model, text representations of IPv6 addresses, definition of IPv6 unicast addresses, anycast addresses, and multicast addresses, and an IPv6 node’s required addresses.

Class A Private Range: 10.0.0.0 to 10.255.255.255

A public IP address is assigned to every computer that connects to the Internet, while private addresses are used to distinguish between computers on the same local area network (LAN).

Public IP addresses will be issued by an Internet Service Provider and will have number ranges from 1 to 191 in the first octet, with the exception of the private address ranges that start at 10.0.0 for Class A private networks and 172.16.0 for the Class B private addresses.

With IPv6, private addresses are called ULA (Unique Local Address), and they are defined by RFC 4193, Unique Local IPv6 Unicast Addresses. The range for IPv6 ULA is fc00::/7, but the lower half of the addresses (fc00::/8) are reserved for a future global authority to assign.