After reading this article you will learn about the format of IP addresses.
In the Internet, every host and every router has a unique address. In other words, no two hosts or routers have the same address. This address is known as the IP address.
This should not be confused with the Internet address. The Internet address is a text string such as “univall(dot)com“. The IP address, on the other hand, is expressed as a series of numbers. This address is expressed by a series of four numbers each separated by a “.” symbol.
The range of Internet addresses at present is from 1.0.0.0 to 239.255.255.255. All IP addresses are 32 bits long and are used in the source and destination address fields of all Internet protocol packets. The first 8 bits are used for the network address (in the class A format); the rest being used for the host address.
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Network numbers or addresses are assigned by Network Information Centre (NIC). Having a single agency to do this avoids any confusion. In addition to the above address scheme, there are also some special addresses.
Details of the IP addresses are as follows. Every host and every router on the Internet has an IP address.
The combination is unique and no two machines on the internet have the same IP address. All IP addresses are 32 bits long and are used in the source address and destination address fields of IP packets. The different classes of addresses and the formats used in these classes are shown in Fig. 10.2.
The ranges of host addresses vary from class to class. These are:
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Class A: Range 1.0.0.0 to 127.255.255.255
Class B: Range 128.0.0.0 to 191.255.255.255
Class C: Range 192.0.0.0 to 223.255.255.255
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Class D: Range 224.0.0.0 to 239.255.255.255
Class E: Range 240.0.0.0 to 247.255.255.255
The network portion including the 0 bit is 8 bits long in class A, with 24 bits for the host addresses (that is up to 224 hosts). In class B, the network address portion consists of 16 bits (with the first two bits being 10) and hence will have 214 network addresses with 216 hosts. In class C, network address portion has up to 24’bits with the first 3 bits being 110 and up to 8 bits for the host address.
The number of host address can be calculated for each class from the above information. There have been additional efforts to allow more addresses through the creation of subnets. But these are being discussed here very briefly.
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Class D is reserved for multicast addresses, class E is reserved for future use and consists of multicast in which a datagram is directed to multiple host with addresses beginning with 11110. Internet addresses, which are 32 bits long, are written in dotted decimal notation. In this scheme, each of 4 bytes is written in decimal from 0 to 255.
For example, the address C0280715 in hexadecimal refers to the address 192.40.7.21. The lowest IP address is 0.0.0.0 and the largest possible is 255.255.255.255. The values 0 and —1 have special meanings. The value 0 refers to this specific network or this specific host. The value of 1 is used to indicate a broadcast address to mean all hosts on the indicated network.