IPv4 Addressing Overview

pigeoneggtrainsNetworking and Communications

Oct 24, 2013 (4 years and 15 days ago)

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IPv4 Addressing Overview

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IP Address


An IP address is a 32
-
bit sequence of 1s and 0s.


To make the IP address easier to use, the address
is usually written as four decimal numbers
separated by periods.


This way of writing the address is called the dotted
decimal format.

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Every IP address has two parts:

1.
Network

2.
Host



IP addresses are divided into
classes A,B and C to define
large, medium, and small
networks.


The Class D address class
was created to enable
multicasting.

IETF (
The
Internet Engineering
Task Force)

reserves Class E
addresses for its own
research
.

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Reserved IP Addresses


Certain host addresses
are reserved and cannot
be assigned to devices on
a network.


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


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

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IP Private Addresses


No two machines that connect to a public network can have
the same IP address because public IP addresses are global
and standardized


Private IP addresses

are a solution to the problem of the
collapse of public IP addresses. Addresses that fall within
these
ranges

are not routed on the Internet backbone:


Connecting a network using private addresses to the Internet
requires the usage of NAT

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Subnet Mask Address


Determines which part of an IP address is the
network field and which part is the host field
.


Follow these steps to determine the subnet
mask:


1. Express the subnetwork IP address in
binary form.


2. Replace the network and subnet portion of
the address with all 1s.


3. Replace the host portion of the address with
all 0s.


4. Convert the binary expression back to
dotted
-
decimal notation.

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Establishing the Subnet Mask Address


To determine the number of bits to be used, the
network designer needs to calculate how many
hosts the largest subnetwork requires and the
number of subnetworks needed.


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Subnetting example

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Variable
-
Length Subnet Mask
-

VLSM


VLSM allows you to use more than one subnet
mask within the same network address space
-

subnetting a subnet

S

Subnet Add

0

207.21.24.0/27

1

207.21.24.32/27

2

207.21.24.64/27

3

207.21.24.96/27

4

207.21.24.128/27

5

207.21.24.160/27

6

207.21.24.192
/
27

7

207.21.24.224/27

Sub
-
sub

Sub
-
Subnet Add

Sub 0

207.21.24.192/
30

Sub 1

207.21.24.196/
30

……..

Sub 5

207.21.24.212/
30

Sub 6

207.21.24.216/
30

Sub 7

207.21.24.220/
30

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Supernetting


Using a bitmask to group multiple classful
networks as a single network address.


Same process with route aggregation.


supernetting

is most often applied when the
aggregated networks are
under common
administrative control.


In class C network addresses,
supernetting

can be used so that the addresses appear as
a single large network, or
supernet

Net #

Net IP

First IP

Last IP

Broadcast IP

1

2

3

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

30

31

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