INTRODUCTION TO IP ADDRESS

Ravi Chandra Gurung

IP ADDRESSES

IP ADDRESSES

WHAT IS AN IP ADDRESS?

An IP address is a unique global address for a network interface

An IP address:

- is a 32 bit long identifier

- encodes a network number (network prefix)

and a host number

DOTTED DECIMAL NOTATION

IP addresses are written in a so-called dotted decimal notation

Each byte is identified by a decimal number in the range [0..255]:

Example: 1000111110000000 10001001 10010000

1st Byte

= 128

2nd Byte

= 143

3rd Byte

= 137

4th Byte

= 144

128.143.137.144

The network prefix identifies a network and the host number identifies a specific host (actually, interface on the network).

How do we know how long the network prefix is? The network prefix is implicitly defined (see class-based addressing) The network prefix is indicated by a netmask.

NETWORK PREFIX AND HOST NUMBER

network prefix host number

Example: ellington.cs.virginia.edu

Network id is: 128.143.0.0

Host number is: 137.144

Network mask is: 255.255.0.0 or ffff0000

Prefix notation: 128.143.137.144/16 Network prefix is 16 bits long

EXAMPLE

128.143 137.144

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 ADDRESS CLASSES

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IP ADDRESS CLASSES

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IP ADDRESSES AS DECIMAL NUMBERS

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HOSTS FOR CLASSES OF IP ADDRESSES

Class A (24 bits for hosts) 224 - 2* = 16,777,214 maximum hosts

Class B (16 bits for hosts) 216 - 2* = 65,534 maximum hosts

Class C (8 bits for hosts) 28 - 2* = 254 maximum hosts

* Subtracting the network and broadcast reserved address

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IPV4 ADDRESS CLASSES

Class D Addresses

A Class D address begins with binary 1110 in the first octet.

First octet range 224 to 239.

Class D address can be used to represent a group of hosts called a host group, or multicast group.

Class E Addresses

First octet of an IP address begins with 1111

First octet range 240 to 255.

Class E addresses are reserved for experimental purposes and should not be used for addressing hosts or multicast groups. 

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IP ADDRESSES AS DECIMAL NUMBERS

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An IP address such as 176.10.255.255 that has all binary 1s in the host bit positions is reserved for the broadcast address.

An IP address such as 176.10.0.0 that has all binary 0s in the host bit positions is reserved for the network address.

NETWORK IDS AND BROADCAST ADDRESSES

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PRIVATE ADDRESSES

DEFINITION

Subnetwork, or subnet, is a logically visible, distinctly addressed part of a single Internet Protocol network.

Subnetting is the division of a computer network into groups of computers that have a common, designated IP address routing prefix.

ADVANTAGES

Allows a single shared network address to split it up into many smaller networks.

Without subnets, organizations would require many network addresses Limited number of Network addresses available

Alleviates traffic Smaller routing tables Alleviates excessive packet collision and congestion

Easier to manage and solve problems

Better Security Separating departments with highly sensitive material

Accounting and Administration