LECTURE 2 IP ADDRESSES IP Addresses Classful Addressing

LECTURE -2 IP ADDRESSES IP Addresses: Classful Addressing 1

CONTENTS • INTRODUCTION • CLASSFUL ADDRESSING • Different Network Classes • Subnetting • Classless Addressing 2

INTRODUCTION 3

WHAT IS AN IP ADDRESS Ø A way to identify machines on a network Ø A unique identifier 4

IP USAGE Ø Used to connect to another computer Ø Allows transfers of files and e-mail 5

IP STRUCTURE Ø IP addresses consist of four sections Ø Each section is 8 bits long Ø Each section can range from 0 to 255 Ø Written, for example, 128. 35. 0. 72 6

IP STRUCTURE Ø These four sections represent the machine itself and the network it is on Ø The network portion is assigned. Ø The host section is determined by the network administrator 7

IP STRUCTURE Ø 5 Classes of IP address A B C D and E Ø Class A reserved for governments Ø Class B reserved for medium companies Ø Class C reserved for small companies 8

IP STRUCTURE Ø Class D are reserved for multicasting Ø Class E are reserved for future use 9

IP STRUCTURE Ø Class A begins 1 to 126 Ø Class B begins 128 to 191 Ø Class C begins 192 to 223 10

What is an IP Address? An IP address is a 32 -bit address. The IP addresses are unique. 11

Address Space …………. . addr 15 addr 2 …………. . addr 41 addr 226 addr 31 …………. . 12

Address space rule …………. . addr 15 …………. . Theaddr 2 address space in a protocol …………. . That uses N-bits to define an addr 41 addr 226 Address is: addr 31 N …………. . 2 …………. . 13

IPv 4 address space The address space of IPv 4 is 232 or 4, 294, 967, 296. 14

Binary Notation 01110101 10010101 00011101010 15

Dotted-decimal notation 16

Hexadecimal Notation 0111 0101 1001 0101 0001 1110 1010 75 95 1 D EA 0 x 75951 DEA 17

Example 1 Change the following IP address from binary notation to dotted-decimal notation. 10000001011 11101111 Solution 129. 11. 239 18

Example 2 Change the following IP address from dotted-decimal notation to binary notation: 111. 56. 45. 78 Solution 19 01101111 00111000 00101101 01001110

Example 3 Find the error in the following IP Address 111. 56. 045. 78 Solution There are no leading zeroes in Dotted-decimal notation (045) 20

Example 3 (continued) Find the error in the following IP Address 75. 45. 301. 14 Solution In decimal notation each number <= 255 301 is out of the range 21

Example 4 Change the following binary IP address Hexadecimal notation 10000001011 11101111 Solution 0 X 810 B 0 BEF or 810 B 0 BEF 16 22

RESERVED ADDRESSES Ø Addresses beginning 127 are reserved for loopback and internal testing Ø xxx. 0. 0. 0 reserved for network address Ø xxx. 255 reserved for broadcast 23

IP ADDRESSES ØIP addresses are: Ø Unique Ø Global and Standardised Ø Essential 24

SUBNETTING - WHY? ØDivision of local networks ØGreater number of networks ØSimplifies addressing 25

SUBNETTING - HOW ØBits borrowed from host field Network Host Network Subnet/Host 26

SUBNETTING -EXAMPLE Ø 130. 5. 0. 0 - Network address Ø 130. 5. 2. 144 - Host address Ø 255. 0 - Subnet Mask Ø 130. 5. 2. 0 - Subnet 27

Occupation of the address space 28

In classful addressing the address space is divided into 5 classes: A, B, C, D, and E. 29

Finding the class in binary notation 30

Finding the address class 31

Example 5 Show that Class A has 231 = 2, 147, 483, 648 addresses 32

Example 6 Find the class of the following IP addresses 00000001011 11101111 11000001011 11101111 Solution • 00000001011 11101111 1 st is 0, hence it is Class A • 11000001011 11101111 1 st and 2 nd bits are 1, and 3 rd bit is 0 hence, Class C 33

Finding the class in decimal notation 34

Example 7 Find the class of the following addresses 158. 223. 1. 108 227. 13. 14. 88 Solution • 158. 223. 1. 108 1 st byte = 158 (128<158<191) class B • 227. 13. 14. 88 1 st byte = 227 (224<227<239) class D 35

IP ADDRESS WITH APPENDING PORT NUMBER 158. 128. 1. 108: 25 the for octet before colon is the IP address The number of colon (25) is the port number 36

Netid and hostid 37

Blocks in class A 38

Millions of class A addresses are wasted. 39

Blocks in class B 40

Many class B addresses are wasted. 41

Blocks in class C 42

The number of addresses in a class C block is smaller than the needs of most organizations. 43

Class D addresses are used for multicasting; there is only one block in this class. 44

Class E addresses are reserved for special purposes; most of the block is wasted. 45

Network Addresses The network address is the first address. The network address defines the network to the rest of the Internet. Given the network address, we can find the class of the address, the block, and the range of 46 the addresses in the block

In classful addressing, the network address (the first address in the block) is the one that is assigned to the organization. 47

Example 8 Given the network address 132. 21. 0. 0, find the class, the block, and the range of the addresses Solution The 1 st byte is between 128 and 191. Hence, Class B The block has a netid of 132. 21. The addresses range from 132. 21. 0. 0 to 132. 21. 255. 48

Mask • A mask is a 32 -bit binary number. • The mask is ANDe. D with IP address to get • The bloc address (Network address) • Mask And IP address = Block Address 49

The network address is the beginning address of each block. It can be found by applying the default mask to any of the addresses in the block (including itself). It retains the netid of the block and sets the hostid to zero. 50

DEFAULT MAK Class A default mask is 255. 0. 0. 0 Class B default mask is 255. 0. 0 Class C Default mask 255. 0 51

SUBNETTING 52

IP addresses are designed with two levels of hierarchy. 53

A network with two levels of hierarchy (not subnetted) 54

A network with three levels of hierarchy (subnetted) 55

THE INTERNET PROTOCOL Ø Running out!! Ø Upgraded to IPv 6 56

QUESTIONS/COMMENTS? 57