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Classful addressing is obsolete and has not been used in the Internet since the implementation of Classless Inter-Domain Routing (CIDR) starting in 1993.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:
“When I think of the gold-diggers and the Mormons, the slaves and the slave-holders and the flibustiers, I naturally dream of a glorious private life. No, I am not patriotic.”
—Henry David Thoreau (1817–1862)
“Surely the writer is to address a world of laborers, and such therefore must be his own discipline.”
—Henry David Thoreau (1817–1862)
“When I consider the short duration of my life, swallowed up in the eternity before and after, the little space which I fill and even can see, engulfed in the infinite immensity of spaces of which I am ignorant and which know me not, I am frightened and am astonished at being here rather than there. For there is no reason why here rather than there, why now rather than then.”
—Blaise Pascal (1623–1662)