This article aims to provide information about IP addresses, subnets, and CIDR notation.
In TCP/IP networking, an IP address is a value assigned to a device on a network for purposes of communication. There are currently two types of addresses, IPv4 (for example, 220.127.116.11) and IPv6 (for example, 2001:0db8:85a3:0000:0000:8a2e:0370:7334).
- IPv4 addresses are 32-bit integers represented in groups of four (4), separated by periods (.). Integers within each group range from 0 to 255. The IPv4 addressing scheme allows for a total of 232 (approximately 4 billion) addresses.
- IPv6 addresses are 128-bit integers represented in hexadecimal, separated by colons (:).
For the purposes of this particular article, we will focus primarily on IPv4
The following is reference table shows all valid CIDR lengths, their associated subnets, class, and supported capacity.
|/23||255.255.254.0 ||2 C||508|
The following is a table showing addresses that are officially reserved.
a single Class A network number
16 contiguous Class B network numbers
256 contiguous Class C network numbers
Special thanks to Ray Smith's website from 1996, located at www.rjsmith.com/CIDR-Table.html for the Reference Table and the majority of the information regarding CIDR that is found on this page.