BIS 411 Lecture 5

8/3/2019 BIS 411 Lecture 5

1/15

10/27/20

BIS 411; Enterprise Network Management

LECTURE FIVE

Topic

IP Addressing and Network Address Translation

Enterprise Network Management Lecture

Slides by: Max well Dorgbefu Jnr.

Introduction Just as index numbers uniquely identify students of an

institution, IP addresses do same for nodes on IP

networks.

Not all IP addresses assigned to nodes on IP networks

are routable over the Internet.

For every node to get connected to the Internet, they

must be assigned a public IP address which are quite

expensive to acquire from ISPs. NAT is used to reduce the number of Public IP

addresses needed to get connected to the Internet.

Enterprise Network Management Lecture Slides by: Maxwell Dorgbefu Jnr.

8/3/2019 BIS 411 Lecture 5

2/15

10/27/20

IP Addressing - 1

One of the most basic components of a TCP/IP

network is IP addressing.

An IP address is a numeric identifier assigned

to computers and other communication

devices on an IP network.

Every device on a TCP/IP network must have a

unique IP address.


IP Addressing - 2

Unlike MAC addresses which are hard-coded on

the NIC , IP addresses are software or logical

addresses.

IPv4 is a 32-bit number.

IPv6 or IPng is a 128-bit number.


8/3/2019 BIS 411 Lecture 5

3/15

10/27/20

IP Addressing Terminologies

Bit This is a binary zero or one (0 or 1).

Octet This refers to 8-bit binary number.

Subnet mask: It is a 32-bit value that allows

the recipient of IP packets to distinguish the

network ID portion from the host ID portion of

a given IP address.


IP Address Format

Every IP address consists of two parts

namely:

Network portion and Host portion as

shown in the figure below:


NETWORK ID HOST ID

8/3/2019 BIS 411 Lecture 5

4/15

10/27/20

IP Address Representation

In IPv4, the IP address is a 32-bit number.

The 32-bit number is represented as 4 octets

each separated by a dot.

E.g. 11000000 . 10101000 . 00000000. 00000010

For simplicity IP addresses are represented in a

decimal notation as 192.168.0.2


Classes of IP Addresses In class-based IP addressing, there are five classes

namely:

Class A

Class B

Class C

Class D

Class E Out of these classes, only classes A,B and C are

considered usable by local Network Administrators.


8/3/2019 BIS 411 Lecture 5

5/15

10/27/20

Usable IP Address Classes


Class A IP Addresses - 1 Class A addresses are designed to support

extremely large networks.

A Class A IP address uses the first octet of the

address to indicate the network ID, and the

remaining three octets are used for the host

ID.

The first bit of a Class A address is always 0.



8/3/2019 BIS 411 Lecture 5

6/15

10/27/20

Lowest number that can be represented is

00000000 (0).

The highest number is 01111111 (127).

However 0 and 127 are reserved and cannot

be used as a network address.

Any IP address that has a value between 1

and 126 inclusive in the first octet is a class Aaddress.

Class A IP Addresses - 2



Class A IP Address



8/3/2019 BIS 411 Lecture 5

7/15

10/27/20

Class B IP Addresses - 1

The class B IP address was designed tosupport the needs of moderate to large-sized

networks.

A class B IP address uses two of the four

octets to indicate the network address and

the remaining two for the host addresses.

The first 2 bits of the first octet of a class B

address are always 10.



Class B IP Addresses - 2

Lowest number that can be represented is

10000000 (128) and the highest number is

101111111 (191).

Any IP address that starts with a value in the

range of 128 to 191 inclusive in the first

octet is a Class B address.



8/3/2019 BIS 411 Lecture 5

8/15

10/27/20

Class B IP Address


Class C IP Addresses

The Class C address was designed to support

small network.

A Class C address begins with binary 110.

The lowest number that can be represented

is 11000000 (192) and the highest is

11011111 (223).

Any IP address that starts with a value in the

range of 192 to 223 inclusive in the first

octet is a Class C address.Enterprise Network Management Lecture


8/3/2019 BIS 411 Lecture 5

9/15

10/27/20

Class C IP Address


Usable IP Address Classes

CLASS FIRST OCTET DEFAULT S M SUPPORT

A 0 - 126 255.0.0.0 Very largeorganizations.

B 128 - 191 255.255.0.0 Medium-sizedorganizations

C192 - 223 255.255.255.0 Small

organizations


8/3/2019 BIS 411 Lecture 5

10/15

10/27/20

Class D IP Addresses

This class of address was created to enablemulticasting in an IP address.

A multicast address is a unique network

address that directs packets that have the

destination address to predefined groups of IP

addresses.

The first 4 bits of a Class D address must be

1110.

The first octet range for Class D address is

11100000 to 11101111, or 224 to 239.Enterprise Network Management Lecture


Class E IP Addresses

The IETF reserves the Class E address for its

own research.

This class of IP address is also referred to as

Experim ental Addresses.

The first 4 bits of a Class E address are always

set to 1.

The first octet range for Class E address is11110000 to 11111111, or 240 to 255.



8/3/2019 BIS 411 Lecture 5

11/15

10/27/20

Private IP Addresses

Private IP addresses are assigned to an

organizations network by the local network

administrator.

Private IP addresses are not routable over the

Internet.

The range of IP addresses that are reserved

(RFC 1918) for private use are given in the next

slide.


Range of Private IP Addresses


Class Range of IP Addresses

A 10.0.0.0 to 10.255.255.255

B 172.16.0.0 to 172.31.255.255

C 192.168.0.0 to 192.168.255.255

8/3/2019 BIS 411 Lecture 5

12/15

10/27/20

Public IP Addresses

Public IP addresses are required by

organizations that need to communicate with

the Internet.

Public IP addresses can be used to route traffic

in the public network.

Public IP addresses are assigned to

organizations by ISPs(Internet Service

Providers).


Classless Inter Domain Routing(CIDR)

Its basically the method that ISPs use to allocate a

number of addresses to a company or a home

customer.

When you receive a block of addresses from an ISP,

what you get will look something like this:

192.168.10.32/28.

This is telling you what your subnet mask is.

The slash notation (/) means how many bits are turnedon (1s).



8/3/2019 BIS 411 Lecture 5

13/15

10/27/20

Some CIDR Values

Subnet Mask CIDR Value

255.0.0.0 /8

255.128.0.0 /9

255.255.0.0 /16

255.255.192.0 /18

255.255.240.0 /20

255.255.255.0 /24

255.255.255.224 /27Enterprise Network Management Lecture


NAT was introduced to slow the depletion ofavailable IP address space by allowing manyprivate IP addresses to be represented by somenumber of public IP addresses.

Situations when NAT is needed include:

You need to connect to the Internet and your hostsdont have globally unique IP addresses.

You change to a new ISP that requires you torenumber your network.

You need to merge two intranets with duplicateaddresses.

Network Address Translation (NAT)



8/3/2019 BIS 411 Lecture 5

14/15

10/27/20

Types of NAT

Static NAT: This is designed to allow a one-to-onemapping between local and global IP addresses.

Dynamic NAT: This gives you the ability to map anunregistered IP address to a registered IP addressfrom/out of a pool of registered IP addresses.

Overloading :This is designed to map multipleunregistered IP addresses to a single registered IP

address(many-to-one) by using different portnumbers.

It is also known as Port Address Translation(PAT).Enterprise Network Management Lecture


Network Address Translation (NAT)



8/3/2019 BIS 411 Lecture 5

15/15

10/27/20

Summary

An IP address uniquely identifies a node on a computernetwork.

In class-based IP addressing, only the first three(3)

classes are usable.

The remaining classes are reserved for special purposes.

Private IP addresses are not routable over the Internet

but public ones are.

ISPs use CIDR to allocate a number of addresses to a

company or a home customer.

NAT makes it easier and less expensive in connecting

LANs to the Internet.Enterprise Network Management Lecture


End of Lecture !!!

Do Not Miss Next Weeks Lecture

on Network Mgt . Models.

Questions & Comments ???.....


Documents

BIS 411 Lecture 5