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IP Addressing

(Internet Protocol)

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Internet Protocol

Numbering scheme

Largest network of computers

American Registry of InternetworkNumbers (ARIN)

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What is an IP address

A way to identify machines on a network

A unique identifier

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IP Addresses

IP addresses are:

Unique

Global and Standardised

Essential

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IP usage

Used to connect to another computer

Allows transfers of files and e-mail

An IP address is 32 bit address.

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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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What is an IP address?

IP (Internet Protocol) address device used by routers, to select best path

from source to destination, across

networks and internetworks

network layer address, consisting of

NETWORK portion, and HOST portion

logical address , assigned in software by

network administrator part of a hierarchical numbering scheme -

unique, for reliable routing.

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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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Finding the class in binary notation

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Finding the address class

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IP structure

Class A begins 0 to 127

Class B begins 128 to 191

Class C begins 192 to 223

Class D begins 224 to 239

Class E begins 240 to 255

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Finding the class in decimal notation

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Class A

1st octet = network address, octets 2-4= host address

1st bits of 1st octet set to 0

Next 7 bits of 1st octet for networkaddress.

00000000 is minimum address and

11111111 is maximum address. 2^7 -2=126 total number of network

addresses (127)

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Class A

2^24 -2 total number of hosts undereach network address in class A.

Network address 0 is reserved to

designate the default route for thepackets.

Addresses beginning 127 are reserved

for internal testing Class A range has address range from

0.0.0.0 to 127.255.255.255.

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Class A

For Example:- 172.19.2.250

172.0.0.0 is the network address.

172.255.255.255 is the broadcast Address

of network address 172.

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Class A IP address

124.224.224.100

01111100 11100000 11100000 01100100

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Class B IP address

1st 2 octets = network address, octets

3-4 = host address

1st bit of 1st octet always set to 1.

2nd bit of 1st octet always set to 0.

Up to (2^14 2) Total Network

Addresses.

up to (2^16- 2) host addresses (65534)

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Class B IP address

129.224.224.100

10000001 11100000 11100000 01100100

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Class C IP address

1st 3 octets = network address, octet 4

= host address

1st 3 bits of 1st octet set to 110

Up to ( 2^21-2) Total no. Of network

addresses.

up to (2^8- 2) host addresses.

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Class C IP address

193.224.224.100

11000001 11100000 11100000 01100100

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Netid and hostid

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Subnet

A network to be split into several parts

for internal use but still act like a single

network to the outside world. In the

internet literature, these parts are calledsubnet.

To outside the network, the subnetting

is not visible, so allocating a new subnetdoes not require contacting NIC or

changing any external databases.

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Subnet Mask Purpose:

Apply the Mask to the IP Address to determine: Network bits

Host bits

Subnet ID, Broadcast ID & Unicast range

Format:4 octets, dotted decimal notation (same as IP address)

Contiguous binary 1s starting from the left

Examples:

255.255.255.0 (typical for LAN)

255.255.255.252 (typical for WAN)

255.255.255.1 (incorrect)

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Subnet Mask in Binary

255.255.255.0

11111111.11111111.11111111.00000000

255.255.255.252 11111111.11111111.11111111.11111100

255.255.255.1 - incorrect

11111111.11111111.11111111.00000001

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Subnet Calculation Step 1 Convert:

decimal address & mask format to binary address & mask

format

Step 2 Apply:

binary subnet mask to the binary IP address using the

and function

Step 3 Calculate:

Subnet IDBroadcast ID

Unicast range (usable subnet addresses)

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How to Calculate Subnet ID

(Binary of subnet Mask) * (Binary of IP

address)= Subnet ID

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Useable IP Address Calculations

1) 32 bits in address2) 32 - network bits = host bits

3) 2 to the power of host bits = addresses on subnet

4) addresses - 2 (Broadcast and Subnet ID)= usable addresses on subnet

For Example:-

32-24=8 host bit

2^8=256 (Addresses on subnet)

256-2=254(usable addresses on subnet)

(broad cast id & subnet id)

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Class DClass D addresses

are used for multicasting;there is onlyone block in this class.

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IP Address Class D and

Multicast

The IPv4 networking standard defines Class D addresses

as reserved for multicast. Multicast is a mechanism for

defining groups of nodes and sending IP messages to thatgroup rather than to every node on the LAN (broadcast) or

just one other node (unicast). Multicast is mainly used on

research networks. As with Class E, Class D addresses

should not be used by ordinary nodes on the Internet.

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IP Address Class E and Limited Broadcast

The IPv4 networking standard defines Class E addresses as reserved,

meaning that they should not be used on IP networks. Some research

organizations use Class E addresses for experimental purposes.

However, nodes that try to use these addresses on the Internet will be

unable to communicate properly. A special type of IP address is thelimited broadcast address 255.255.255.255. A broadcast involves

delivering a message from one sender to many recipients. Senders

direct an IP broadcast to 255.255.255.255 to indicate all other nodes on

the local network (LAN) should pick up that message. This broadcastis 'limited' in that it does not reach every node on the Internet, only

nodes on the LAN.

http://compnetworking.about.com/library/glossary/bldef-node.htmhttp://compnetworking.about.com/library/glossary/bldef-lan.htmhttp://compnetworking.about.com/library/glossary/bldef-lan.htmhttp://compnetworking.about.com/library/glossary/bldef-node.htm