The IP addresses are unique. The address space of IPv4 is 2 32 or 4,294,967,296.

Octet IP address format is dotted decimal. Dotted decimal makes it easy to work with IP addresses.

Example = =

Multicast Research *

Example Find the class of each address:

Solution The first byte is 227 (between 224 and 239); the class is D The first byte is 193 (between 192 and 223); the class is C The first byte is 14 (between 0 and 127); the class is A The first byte is 252 (between 240 and 255); the class is E The first byte is 134 (between 128 and 191); the class is B. IP Addressing and Subnetting Page 6

Multicast Research IP Address Classes

In classful addressing, an IP address in class A, B and C is divided into two parts netid and hostid. These parts are varying length, depending on the class of the address.

ClassNumber of Network bitsNumber of Host bits A824 B16 C248 Number of Network Bits and Host Bits in each class

ClassNumber of NetworksNumber of Hosts A B 2 16 C NNNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH 2 8 = = Number of Networks and Hosts Per each Network

2 Number of Network bits = Number of Networks 2 Number of Host bits = Number Hosts Number of Networks and Hosts Per each Network

ClassDefault Subnet Mask A B C Subnet Mask

ClassDefault Subnet Mask A B C ClassNumber of Network bitsNumber of Host bits A824 B16 C248 The subnet mask determine which part of the address belongs to the Network address and which part belongs to the Host address Subnet Mask Number of Zeros in subnet mask represent the number of Host bits

Every host and router on the Internet has an IP address, which encodes its network number and host number. All IP addresses are 32 bits long. It is important to note that an IP address does not actually refer to a host. It really refers to a network interface, so if a host is on two networks, it must have two IP addresses. IP addresses were divided into the five categories 14 network mask

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18 Frame format IPV4

19 1.All IP addresses have a network and host portion. 2.In classful addressing, the network portion ends on one of the separating dots in the address (on an octet boundary). 3.Classful addressing divides an IP address into the Network and Host portions along octet boundaries. 4.In the classful addressing system all the IP addresses that are available are divided into the five classes A,B,C,D and E, in which class A,B and C address are frequently used because class D is for Multicast and is rarely used and class E is reserved and is not currently used.

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21 1.Each of the IP address belongs to a particular class that's why they are classful addresses. 2.Earlier this addressing system did not have any name,but when classless addressing system name into existence then it is named as Classful addressing system. 3.The main disadvantage of classful addressing is that it limited the flexibility and number of addresses that can be assigned to any device. 4.One of the major disadvantage of classful addressing is that it does not send subnet information but it will send the complete network address. 5.The router will supply its own subnet mask based on its locally configured subnets. As long as you have the same subnet mask and the network is contiguous, you can use subnets of a classful network address.

22 Classless addressing uses a variable number of bits for the network and host portions of the address.

Decimal Binary bits host 23 1.Classless addressing treats the IP address as a 32 bit stream of ones and zeroes, where the boundary between network and host portions can fall anywhere between bit 0 and bit Classless addressing system is also known as CIDR(Classless Inter- Domain Routing). 3.Classless addressing is a way to allocate and specify the Internet addresses used in inter-domain routing more flexibly than with the original system of Internet Protocol (IP) address classes. 4. CIDR (Classless Internet Domain Routing), defines arbitrarily-sized subnets solely by base address and number of significant bits in the address. 5.A CIDR address of /24 defines a block of addresses in the range through , while /20 would define a network 16 times as large - from through

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25 1.The 32-bit IP address contains information about the host and its network. 2.It is very necessary to distinguish both. 3.For this, routers use Subnet Mask, which is as long as the size of the network address in the IP address. 4.Subnet Mask is also 32 bits long. I 5.f the IP address in binary is ANDed with its Subnet Mask, the result yields the Network address. 6.For example, say the IP Address is and the Subnet Mask is then: 7. This way the Subnet Mask helps extract the Network ID and the Host from an IP Address. It can be identified now that is the Network number and is the host on that network.