Of all the billions of computers connected to the Internet, each one has a unique, identifying number assigned to it called an IP address. These numbers are based on combinations of binary numbers (0 and 1) grouped into “octets.” While the binary IP address form contains four groups of eight digits with only 0s and 1s (such as 01010101. 01010101. 01010101. 01010101), the IP address that you actually see is expressed in a dotted decimal format (such as 255.255.255.255).
The dotted decimal format makes it easier for humans to work with these long binary numbers.
When you think about all those 0s and 1s, it becomes almost mindboggling. Over 4.3 billion combinations are available using the four octets.
But these numbers aren’t just random, IP address octets are broken down into “Net” and “Host” (also called “node) octets. This is known and subnetting. For example, the first set of numbers belongs to the Net section which is used to identify which network the computer belongs to. The Host section identifies the computer itself with the last octet always being included in this section.
Some IP addresses are reserved for special purposes based on an organization’s size and need. These include the following classes and addresses:
- 0.0.0.0 - The Default Network
- 1 - 126 (first octet represents the Net identifier) - Class A IP addresses are used for large organizations and account for half of all total available IP addresses.
- 127.0.0.1 - The Loopback Address (often used in troubleshooting. This address is used by host computers to send messages back to itself
- 128 - 191 (first and second octet included in the Net identifier) - Class B IP addresses are typically used for medium-sized networks such as college campuses. These IP addresses account for about one quarter of all available IP addresses.
- 192-223 (first, second and third octet included in the Net identifier) - Class C IP addresses are used for smaller networks
- 224 (first octet represents the Net identifier) - Class D IP addresses are used for multicasts
- 255.255.255.255 - Broadcast IP addresses are used for sending messages to all computers on a network
- Experimental IP addresses are Class E addresses
Think that 4.3 billion IP addresses aren’t enough? As the Internet continues to grow, there’s a good chance that 4.3 billion IP addresses won’t be enough. That’s why a new IP version 6 protocol has been designed to accommodate 128 bits (instead of 8) grouping.
Depending on your network (home, corporate, or Internet), you may run into several instances where you must deal with IP addresses. For example, on a home network, your router and each computer on your system as well as connected devices such as network printers will each have an IP address such as 0.0.0.1, 0.0.0.2, and so on. Each device on your own network will have a unique IP address in relation to your individual network. Your neighbor’s home network may use similar, if not identical IP addresses.
