Private IPv4 Address Spaces
The Internet Engineering Task Force (IETF) has directed the Internet Assigned Numbers Authority (IANA) to reserve the following IPv4 address ranges for private networks, as published in RFC 1918:
| RFC1918 name | IP address range | number of addresses | classful description | largest CIDR block (subnet mask) | host id size | mask bits |
|---|---|---|---|---|---|---|
| 24-bit block | 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 | 8 bits |
| 20-bit block | 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 | 12 bits |
| 16-bit block | 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 | 16 bits |
Classful addressing is obsolete and has not been used in the Internet since the implementation of Classless Inter-Domain Routing (CIDR) starting in 1993. For example, while 10.0.0.0/8 was a single class A network, it is common for organizations to divide it into smaller /16 or /24 networks. Contrary to a common misconception, a /16 subnet of a class A network is not referred to as a class B network. Likewise, a /24 subnet of a class A or B network is not referred to as a class C network. The class is determined by the first three bits of the prefix.
Read more about this topic: Private Network
Famous quotes containing the words private, address and/or spaces:
“The decision to have a child is both a private and a public decision, for children are our collective future.”
—Sylvia Ann Hewitt (20th century)
“In the mythus a superhuman intelligence uses the unconscious thoughts and dreams of men as its hieroglyphics to address men unborn.”
—Henry David Thoreau (1817–1862)
“Though there were numerous vessels at this great distance in the horizon on every side, yet the vast spaces between them, like the spaces between the stars,—far as they were distant from us, so were they from one another,—nay, some were twice as far from each other as from us,—impressed us with a sense of the immensity of the ocean, the “unfruitful ocean,” as it has been called, and we could see what proportion man and his works bear to the globe.”
—Henry David Thoreau (1817–1862)