IP Address Tutorial

Page 4: Classification of IP Address

Up to now, you may begin to wonder. Why the IP Address consists of 4 sets of number? And the IP Address is formed by Network Address (Net) and Computer (Host)?

Actually the reason is quite obvious. It allows to classify the IP Address according to the size of corporation – organization, companies, etc…

In the Format of IP Address, we learned that IP Address consists of four set of binary number with the length of 8 bits. According to the theory of mathematics, the total number of permutation of each set of number is 256 (8th root of 2, i.e. 2x2x2x2x2x2x2x2=256). Therefore each set of number can consist of number in the range of 0 – 255.

As we knew that the total length of IP Address is 32 Bits. Therefore the total number of permutation of IP Address is 32th root of 2, i.e. 4,294,967,296 (2x2x….. total 32 times …..x2x2 = 4,294,967,296). Or 42 billion 94 million IP Addresses! Unless the total number of computers connected with the Internet exceed 42 billion, the structure of IP Address never need to change. By the time of writing this tutorial in year 2002, it seems that there is no need to change this structure of IP Address in the near future.

In order to allocate the resources effectively, the IP ddress is divided into 5 categories (Class) and some designated special address. We will discuss the most common three classes – Class A, Class B and Class C.

Class of IP	Explain
0.0.0.0.0	This is not a class of IP Address. Therefore this address do not represent a computer on the Internet. It only represents the network itself.
Class A	Class A IP Address is mainly for the use of huge network, for example, Government organization and big corporation. The following are some corporation and organization using Class A IP Address: IBM Corporation Hewlett-Packard Company Digital Equipment Corporation Apple Computer Inc. Ford Motor Company Standford University U.S. Postal Service etc… The first set of address represent the network. It ranges from 1 to 127. The other three sets of address represent each host in this network. Example: 1.0.0.0 1.0.0.1 1.0.0.2 ————— ————— 1.255.255.255 2.0.0.0 2.0.0.1 2.0.0.2 ————— ————— ————— 125.255.255.255 126.0.0.0 126.0.0.1 —————- —————- 126.255.255.254 126.255.255.255 127.0.0.1 127.0.0.2 127.0.0.3 —————- —————- 127.255.255.254 127.255.255.255 With this combination, we can calculate the following: A total 127 Class A networks are allowed on the Internet. And 16,777,214 hosts are allowed in each Class A network. With 127 Class A network on the Internet, it provides a total of 2,147,483,648 IP Addresses. Class A network occupy half of the IP Address on the Internet.
127.0.0.0	This is not a class of IP Address. Therefore this address do not represent a computer on the Internet. This address also called Loop-back address, usually used to test the host. When using this Loop-back address to send data, the Network Card will not send the data out the network. In stead, the data will be sent back to the host. Therefore it can be used to test if the host has been installed or configured properly.
Class B	The Class B IP Address is mainly for medium sized network. The 1st set of address ranges from 128 to 191 The 1st set and 2nd set of addresses of Class B represent the Network. The other two set of addresses represent each host in this network. Examples: 128.0.0.0 128.0.0.1 128.0.0.2 ————— ————— 128.255.255.255 129.0.0.0 129.0.0.1 129.0.0.2 ————— ————— ————— 190.255.255.255 191.0.0.0 191.0.0.1 —————– —————– 191.255.255.255 With this combination, we can calculate the following: A total 16,384 Class B networks are allowed on the Internet. And 65,534 hosts are allowed in each Class B network. With 16,384 Class B network on the Internet, it provides a total of 1,073,741,824 IP Addresses. Class B network occupy a quarter of the IP Address on the Internet.
Class C	Class C IP Address is the most common IP Adress that we always meet. Class C IP Address is mainly for medium to small sized network. The 1st set address range from 192 to 223. The 1st set, 2nd set and 3rd set of addresses of Class C represent the Network. The 4th set of address represent each host in this network. Example: 192.0.0.0 192.0.0.1 192.0.0.2 ————— ————— 192.255.255.255 193.0.0.0 193.0.0.1 193.0.0.2 —————- —————- —————- 222.255.255.255 223.0.0.0 223.0.0.1 —————— —————— 223.255.255.255 With this combination, we can calculate the following: A total 2,097,152 Class C networks are allowed on the Internet. And 256 hosts are allowed in each ClassC network. With 2,097,152 Class C network on the Internet, it provides a total of 536,870,912 IP Addresses. Class B network occupy 1/8 of the IP Address on the Internet.
Class D and E	The IP Addresses range from 224.0.0.0.0 to 225.225.255.254 usually classified as Class D and Class E. We rarely meet Class D and Class E IP Address, mainly used for Mulicasts and Laboratories. Class D and Class E IP Address will not discuss in this tutorial.
255.255.255.255	IP Address 255.255.255.255 is the Broadcasting Address of a Local Area Network, and will not discuss in this tutorial.

This is the end of IP Address classification tutorial.