Ip Addresses And Subnetting

IP Addresses and Subnetting By Kr. Rajeev Ranjan NIT Hamirpur, HP

07438

Introduction The Internet Protocol (IP) is a protocol used for communicating data across a packet-switched internetwork using the Internet Protocol Suite.

Version of IP Addresses:  IPv0 to IPv15 (Only IPv4 and Ipv6 used in Networking)

IPv4 ( IP version 4) Addresses are 32 bits long. IPv6 ( IP version 6) addresses are 128 bits long.

Characteristics of IPv4  32 bit binary number(4 octet) is used to specify IP address(Hierarchical).

172.16.20.143 network 32-bits

host

 Specifies both network and host.  Number of bits allocated to specify network varies. Total no. of IP addresses in IPv4 is 4.3 billion.

Classification:  Classfull IP Address  Public IP

Classless IP Address Private IP

Classfull IP address classes  IP divided into 5 Classes. IP Classes

A Class A: Class B: Class C: Class D: Class E:

B

C

D

E

(0-127).(0-255).(0-255).(0-255) (128-191).(0-255).(0-255).(0-255) (192-223).(0-255).(0-255).(0-255) (224-239).(0-255).(0-255).(0-255) (140-225). 0-255).(0-255).(0-255) #Network, Host.

Class A IP Address Identify : N

H

H

H

The first (leftmost) bit of a Class A address is always 0 Example of a Class A IP address is 124.95.10.50 The first octet, 124 is assigned by ARIN The administrators assign the remaining 24 bits. The first octet of its IP address range from 0-126. 127 is reserved for special purpose

Class A IP Address Features : All Class A IP addresses use only the first 8 bits to identify the network part of the address The remaining three octets can be used for the host portion of the address Class A network IP up to 2 to-the-power of 24 (224) (minus 2), or 16,777,214, possible IP addresses to devices that are attached to its network Valid Host Range 10.0.0.1 to 10.255.255.254 10.0.0.0 is Network address & 10.255.255.255 is Broadcast Address

Class B IP Address Identify : N

N

H

H

The first 2 bits of a Class B address are always 10 (one and zero). The first two octets identify the network number assigned by ARIN The internal administrators of the network assign the remaining 16 bits Class B IP addresses always have values ranging from 128 to 191 in their first octet

Class B IP Address Features : All Class A IP addresses use only the first 16 bits to identify the network part of the address The remaining two octets can be used for the host portion of the address A Class B IP address can have up to 2 to-the-power of 16 (216) (minus 2 again!), or 65,534, possible IP addresses to devices that are attached to its network  Valid Host Range 172.16.0.1 to 172.16.255.254 172.16.0.0 is Network address & 172.16.255.255 is Broadcast Address

Class C IP Address Identify : N

N

N

H

The first 3 bits of a Class C address are always 110 (one,one and zero). The first three octets identify the network number assigned by ARIN The internal administrators of the network assign the remaining 8 bits Class c IP addresses always have values ranging from 192 to 223 in their first octet

Class C IP Address Features : All Class C IP addresses use the first 24 bits to identify the network part of the address The remaining one octets can be used for the host portion of the address A Class C IP address can have up to 28 (minus 2), or 254, possible IP addresses to devices that are attached to its network Valid Host Range 192.168.100.1 to 192.168.100.254 192.168.100.0 is Network address & 192.168.100.255 is Broadcast Address

IP Address Space  Originally, 3 Classes – A, B, C

 Problem – Classes too rigid (C too small, B too big)

 Solution – Subnetting (e.g. within Stanford) – Classless Interdomain Routing (CIDR)

Subnetting What it is? NETWORK

SUBNET

HOST

Especially large networks need to be divided into smaller networks. These smaller divisions are called subnetworks and provide addressing flexibility. Most of the time subnetworks are simply referred to as subnets. Similar to the host number portion of Class A, Class B, and Class C addresses, subnet addresses are assigned locally, usually by the network administrator Like other IP addresses, each subnet address is unique

Host/subnet Schemes Important Decision To determine the optimal number of subnets and hosts

For Class C IP Address If 2 or 6 bits for subnetting then total hosts 124 (49 % used).  If 3 or 5 bits for subnetting then total hosts 180 (71 % used). If 4 bits for subnetting then total hosts 196 (77 % used).

Subnetting analogy

NETWORK

SUBNET

HOST Subnetting

Area Code

Exchanges

Subscribers

Telephony

Subnetting Real Purpose A primary reason for using subnets is to reduce the size of a broadcast domain.

Explanation When broadcast traffic begins to consume too much of the available bandwidth, network administrators may choose to reduce the size of the broadcast domain.

Subnet Mask What it is? Not an address It determines which part of an IP address is the network field and which part is the host field. A subnet mask is 32 bits long and has 4 octets, just like an IP address

Subnet Mask Determine the subnet mask ? Express the subnetwork IP address in binary form. Replace the network and subnet portion of the address with all 1s. Replace the host portion of the address with all 0s. As the last step convert the binary expression back to dotteddecimal notation.

Subnet Mask Default : Class B Address 16 20

172

143

Default Class B Subnet Mask 255

255 0 8-bit Subnet Mask

0

255

255

0

255

The Anding Operation For What ? For routing a data packet, the router first determines the destination network/subnet address by performing a logical AND using the destination host's IP address and the subnet mask. The result will be the network/subnet address. 131.108.2.2

10000011 01101100 00000010 00000010 &

255.255.255.0

11111111 11111111 11111111

131.108.2.0

10000011 01101100 00000010

00000000 00000000

Sending A Message through IP:

Computer Centre