ip addresses: classful addressing · •classful addressing •different network classes...

IP Addresses:

Classful Addressing

LECTURE -3 IP ADDRESSES

1

CONTENTS

• INTRODUCTION

• CLASSFUL ADDRESSING

• Different Network Classes

• Subnetting

• Classless Addressing

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INTRODUCTION

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WHAT IS AN IP ADDRESS

A way to identify machines on a network

A unique identifier

4

IP USAGE

Used to connect to another computer

Allows transfers of files and e-mail

5

IP STRUCTURE

IP addresses consist of four sections

Each section is 8 bits long

Each section can range from 0 to 255

Written, for example, 128.35.0.72

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IP STRUCTURE

These four sections represent the machine itself

and the network it is on

The network portion is assigned.

The host section is determined by the network

administrator

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IP STRUCTURE

5 Classes of IP address A B C D and E

Class A reserved for governments

Class B reserved for medium companies

Class C reserved for small companies

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IP STRUCTURE

Class D are reserved for multicasting

Class E are reserved for future use

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IP STRUCTURE

Class A begins 1 to 126

Class B begins 128 to

191

Class C begins 192 to

223

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An IP address is a

32-bit

address.

What is an IP Address?

The IP addresses

are

unique. 11

Address Space

addr15addr1

addr2

addr41addr31

addr226

…………..…………..

…………..…………..

…………..

…………..…………..

12

Address space rule

addr15addr1

addr2

addr41addr31

addr226

…………..…………..

…………..…………..

…………..

…………..…………..

The address space in a protocol

That uses N-bits to define an

Address is:

2N

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The address space of IPv4 is

232

or

4,294,967,296.

IPv4 address space

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01110101 10010101 00011101 11101010

Binary Notation

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Dotted-decimal notation

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0111 0101 1001 0101 0001 1101 1110 1010

Hexadecimal Notation

75 95 1D EA

0x75951DEA

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Example 1

Change the following IP address from

binary notation to dotted-decimal

notation.

10000001 00001011 00001011

11101111Solution

129.11.11.23918

Example 2

Change the following IP address

from dotted-decimal notation to

binary notation:

111.56.45.78

Solution

01101111 00111000 00101101 0100111019

Example 3

Solution

Find the error in the following IP Address

111.56.045.78

There are no leading zeroes in

Dotted-decimal notation (045) 20

Example 3 (continued)

Solution

Find the error in the following IP Address

75.45.301.14

In decimal notation each number <= 255

301 is out of the range21

Example 4

Solution

Change the following binary IP address

Hexadecimal notation

10000001 00001011 00001011 11101111

0X810B0BEF or 810B0BEF16 22

RESERVED ADDRESSES

Addresses beginning 127 are reserved for

loopback and internal testing

xxx.0.0.0 reserved for network address

xxx.255.255.255 reserved for broadcast

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IP ADDRESSES

IP addresses are:

Unique

Global and Standardised

Essential

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SUBNETTING - WHY?

Division of local networks

Greater number of networks

Simplifies addressing

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SUBNETTING - HOW

Bits borrowed from host field

Network Network Host Host

Network Network Subnet Host

Network Network Subnet Subnet/Host

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SUBNETTING -EXAMPLE

130.5.0.0 - Network address

130.5.2.144 - Host address

255.255.255.0 - Subnet Mask

130.5.2.0 - Subnet

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Occupation of the address space

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In classful addressing the address space is

divided into 5 classes:

A, B, C, D, and E.

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Finding the class in binary notation

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Finding the address class

31

Show that Class A has

231 = 2,147,483,648 addresses

Example 5

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Example 6

Solution

Find the class of the following IP addresses

00000001 00001011 00001011 11101111

11000001 00001011 00001011 11101111

•00000001 00001011 00001011 11101111

1st is 0, hence it is Class A

•11000001 00001011 00001011 111011111st and 2nd bits are 1, and 3rd bit is 0 hence, Class C

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Finding the class in decimal notation

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Example 7

Solution

Find the class of the following addresses

158.223.1.108

227.13.14.88

•158.223.1.108

1st byte = 158 (128<158<191) class B

•227.13.14.88

1st 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

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Netid and hostid

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Blocks in class A

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Millions of class A addresses

are wasted.

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Blocks in class B

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Many class B addresses

are wasted.

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Blocks in class C

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The number of addresses in

a class C block

is smaller than

the needs of most organizations.

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Class D addresses

are used for multicasting;

there is only

one block in this class.

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Class E addresses are reserved

for special purposes;

most of the block is wasted.

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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 the addresses in the block 46

In classful addressing,

the network address

(the first address in the block)

is the one that is assigned

to the organization.

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Example 8

Solution

Given the network address 132.21.0.0, find the

class, the block, and the range of the addresses

The 1st 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 132.21.255.255.48

Mask

• A mask is a 32-bit binary number.

• The mask is ANDeD with IP address to get

• The bloc address (Network address)

• Mask And IP address = Block Address

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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 255.255.0.0

Class C Default mask 255.255.255.0

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SUBNETTING

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IP addresses are designed with

two levels of hierarchy.

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A network with two levels of

hierarchy (not subnetted)

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A network with three levels of

hierarchy (subnetted)

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THE INTERNET PROTOCOL

Running out!!

Upgraded to IPv6

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QUESTIONS/COMMENTS?

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