IP Addresses: Classful Addressing Lecture -2 IP Addresses IP Addresses: Classful Addressing

CONTENTS INTRODUCTION CLASSFUL ADDRESSING Different Network Classes Subnetting Classless Addressing

INTRODUCTION

What is an IP address A way to identify machines on a network A unique identifier

IP usage Used to connect to another computer Allows transfers of files and e-mail If you want to connect to another computer, transfer files to or from another computer, or send an e-mail message, you first need to know where the other computer is - you need the computer's "address." An IP (Internet Protocol) address is an identifier for a particular machine on a particular network; it is part of a scheme to identify computers on the Internet. IP addresses are also referred to as IP numbers and Internet addresses

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 An IP address consists of four sections separated by dots. Commonly written in decimal Each section contains a number ranging from 0 to 255. Example = 128.35.0.72

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 These four sections represent both the machine itself, or host, and the network that the host is on. The network portion of the IP address is allocated under authority of the Internet Assigned Numbers Authority (IANA). American Registry of Internetwork Numbers (ARIN) Network administrators then assign the host portion of the IP address to the machines on the networks that they operate

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 Which sections of the IP address represent the network and which sections represent the machine will depend on what "class" of IP address is assigned to a network. There are 5 classes of IP addresses: Class A, Class B, Class C, Class D, and Class E.   Class A - supports 16 million hosts on each of 127 networks Class B - supports 65,000 hosts on each of 16,000 networks Class C - supports 254 hosts on each of 2 million networks

IP structure Class D are reserved for multicasting Class E are reserved for future use

IP structure Class A begins 1 to 126 Class B begins 128 to 191 Class C begins 192 to 223 Classes correspond either to the size of the network (the number of hosts that the network can support) or are reserved for specific purposes, such as multicasting and experimentation. The diagram shows Class A, Class B and Class C IP addresses. The blue numbers represent the network and the red numbers represent hosts on the network. As has been mentioned, a Class A network can support many more hosts than a Class C network. You can determine which class any IP address is in by examining the first 4 bits of the IP address. Class A addresses begin with 0xxx, or 1 to 126 decimal. Class B addresses begin with 10xx, or 128 to 191 decimal. Class C addresses begin with 110x, or 192 to 223 decimal. Class D addresses begin with 1110, or 224 to 239 decimal. Class E addresses begin with 1111, or 240 to 254 decimal. Addresses beginning with 01111111, or 127 decimal, are reserved for loopback and for internal testing on a local machine. [You can test this: you should always be able to ping 127.0.0.1, which points to yourself] Class D addresses are reserved for multicasting. Class E addresses are reserved for future use. They should not be used for host addresses.

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

Address Space ………….. addr1 addr15 addr2 ………….. ………….. ………….. addr226

Address space rule 2N ………….. addr1 addr15 addr2 ………….. The address space in a protocol That uses N-bits to define an Address is: 2N ………….. ………….. ………….. addr41 addr226 addr31 ………….. …………..

The address space of IPv4 is IPv4 address space The address space of IPv4 is 232 or 4,294,967,296.

Binary Notation 01110101 10010101 00011101 11101010

Dotted-decimal notation

Hexadecimal Notation 0111 0101 1001 0101 0001 1101 1110 1010 75 95 1D EA 0x75951DEA

Example 1 Change the following IP address from binary notation to dotted-decimal notation. 10000001 00001011 00001011 11101111 Solution 129.11.11.239

Example 2 Change the following IP address from dotted-decimal notation to binary notation: 111.56.45.78 Solution 01101111 00111000 00101101 01001110

Example 3 Solution Find the error in the following IP Address 111.56.045.78 Solution There are no leading zeroes in Dotted-decimal notation (045)

Example 3 (continued) Solution 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

Change the following binary IP address Example 4 Change the following binary IP address Hexadecimal notation 10000001 00001011 00001011 11101111 Solution 0X810B0BEF or 810B0BEF16

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 Loopback Routers use the network address in the forwarding of data. Also, Hosts can only communicate directly with devices using the same network address. Broadcast allows a message to be sent to all devices on a network

IP Addresses IP addresses are: Unique Global and Standardised Essential IP addresses are unique. No two machines can have the same IP number. IP addresses are also global and standardized. All machines connected to the Internet agree to use the same scheme for establishing an address.

Subnetting - Why? Division of local networks Greater number of networks Simplifies addressing

Subnetting - How Bits borrowed from host field Network Host Network Subnet/Host

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

Occupation of the address space

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

Finding the class in binary notation

Finding the address class

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

Solution Example 6 Find the class of the following IP addresses 00000001 00001011 00001011 11101111 11000001 00001011 00001011 11101111 Solution 00000001 00001011 00001011 11101111 1st is 0, hence it is Class A 11000001 00001011 00001011 11101111 1st and 2nd bits are 1, and 3rd bit is 0 hence, Class C

Finding the class in decimal notation

Solution Example 7 Find the class of the following addresses 158.223.1.108 227.13.14.88 Solution 158.223.1.108 1st byte = 158 (128<158<191) class B 227.13.14.88 1st byte = 227 (224<227<239) class D

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

Netid and hostid

Blocks in class A

Millions of class A addresses are wasted.

Blocks in class B

Many class B addresses are wasted.

Blocks in class C

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

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

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

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

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

Solution Example 8 Given the network address 132.21.0.0, find the class, the block, and the range of the addresses Solution 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.

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

The network address is the beginning address of each block 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.

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

SUBNETTING

IP addresses are designed with two levels of hierarchy.

A network with two levels of hierarchy (not subnetted)

A network with three levels of hierarchy (subnetted)

The Internet Protocol Running out!! Upgraded to IPv6

Questions/Comments?