Computer Networks CCNA 1 & 2 - Weebly Networks CCNA 1 & 2 3rd Stage Academic Year 2016-2017 Lecturer ... network then tap into this nearby cable. Early Ethernet networks commonly

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Lavin institute CCNA1&2

Computer Networks

CCNA 1 & 2

3rd Stage

Academic Year

2016-2017

Lecturer

AWDANG AZIZ HUSSIN

Connect us: instlaven.weebly.com

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Networking Fundamentals

a network is a group of connected devices, such as computers and printer,

that communicate either wirelessly or via a cable.

Computer networks are no longer relegated to allowing a group of

computers to access a common set of files stored on a computer designated

as a file server. Instead, with the building of high-speed, highly redundant

networks, network architects are seeing the wisdom of placing a variety of

traffic types on a single network. Examples include voice and video, in

addition to data.

The Purpose of Networks

At its essence, a network’s purpose is to make connections. These

connections might be between a PC and a printer or between a laptop and

the Internet, as just a couple of examples. However, the true value of a

network comes from the traffic flowing over those connections. Consider a

sampling of applications that can travel over a network’s connections:

File sharing between two computers.

Video chatting between computers located in different parts of the

world.

Surfing the web (for example, to use social media sites, watch

streaming video, or to listen to an Internet radio station).

Instant messaging (IM) between computers with IM software

installed.

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E-mail.

Voice over IP (VoIP), to replace traditional telephony systems.

A term commonly given to a network transporting multiple types of traffic

(for example, voice, video, and data) is a converged network. A converged

network might offer significant cost savings to organizations that

previously supported separate network infrastructures for voice, data, and

video traffic. This convergence can also potentially reduce staffing costs,

because only a single network needs to be maintained, rather than separate

networks for separate traffic types.

Primary Building Blocks used to Construct Network

The webs of data or information networks vary in size and capabilities, but

all networks have four basic elements in common:

■Rules or agreements: Rules or agreements (protocols) govern how the

messages are sent, directed, received, and interpreted.

■Messages: The messages or units of information travel from one device to

another.

■Medium: A medium is a means of interconnecting these devices, that is, a

medium can transport the messages from one device to another.

■Devices: Devices on the network exchange messages with each other.

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Early networks had varying standards and, as a result, could not

communicate easily with each other. Now global standardization of these

elements enables easy communication between networks regardless of the

equipment manufacturer.

Common Terms used in Computer Network

Designing, installing, administering, and troubleshooting a network

requires the ability to recognize various network terms.

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The following list describes the network components and the functions they

serve:

■Client: The term client defines the device an end user uses to access a

network. This device might be a workstation, laptop, smartphone with

wireless capabilities, or a variety of other end-user terminal devices.

■ Server: A server, as the name suggests, serves up resources to a network.

These resources might include e-mail access as provided by an e-mail

server, web pages as provided by a web server, or files available on a file

server.

■ Interconnecting Device: Devices such as switch or hub that interconnect

network components, such as clients and servers. A hub is an older and

slower interconnect device. Like a hub, a switch connects computers in a

network but switch tracks the location of the computers on network and is

faster than hub. Router is also Interconnecting device that interconnects two

or more networks.

■ Network Interface Card (NIC): A device that allows computers to

connect to network.

■ Media: The network devices need to be interconnected via some sort of

media. The medium that physically carries the message can change several

times between the sender and the receiver. Network connections can be

wired or wireless.

In wired connections, the medium is either copper, which carries electrical

signals, or optical fiber, which carries light signals. In wireless connections,

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the medium is the Earth’s atmosphere, or space, and the signals are radio

waves.

■Standard: A network standard is in short a reference model to make sure

products of different vendors can work together in a network, The

International Organization for Standardization (ISO) lays out and those

standards.

■Protocol: In networking, the specification of a set of rules for a particular

type of communication.

The term is also used to refer to the software that implements a protocol.

Computer Networking Models

One way to categorize networks is based on where network resources

reside. There are two networking models:

1-Peer-to-Peer Networks.

Peer-to-peer networks allow interconnected devices (for example, PCs) to

share their resources with one another. Those resources could be, for

example, files or printers Peer-to-peer networks are commonly seen in

smaller businesses and in homes. The popularity of these peer-to-peer

networks is fueled in part by client operating systems that support file and

print sharing. Scalability for peer-to-peer networks is a concern, however.

Specifically, as the number of devices (that is, peers) increases, the

administration burden increases. For example, a network administrator

might have to manage file permissions on multiple devices, as opposed to a

single server.

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.

Advantages of Peer-to-Peer Networks

■Cost—Because peer-to-peer networking does not require a dedicated

server.

■Ease of installation—The built-in support for peer-to-peer networking in

modern operating systems makes installing and configuring a peer-to-peer

network a straightforward process.

■Maintenance—A small peer-to-peer network is easy to maintain and

does not require specialized staff or training.

Disadvantages of Peer-to-Peer Networks

■ Security—In a decentralized model, a network wide security policy

cannot be enforced from a server; rather, security needs to be applied to

each computer and resource individually.

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■Data backup—Because files and data are located on individual

computers, each system must have its data backed up individually.

■Limited numbers of computers—Peer-to-peer networking is effective

only on small networks (fewer than 10 computers).

2- Client-Server Networks.

Client/server networks are commonly used by businesses. Because

resources are located on one or more servers, administration is simpler than

trying to administer network resources on multiple peer devices.

Advantages of Client-Server Networks

■Centralized management and security—The ability to manage the

network from a single location.

■Scalability—In a server-based network, administrators can easily add

computers and devices.

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■Simplified backups—On server-based networks, files and folders

typically reside in a single location.

Disadvantages of Client-Server Networks

■High cost—A server-based network requires additional hardware and

software.

■Administration requirements—Client/server networks require

additional administrative skills.

■Single point of failure- If the server fails, the clients can’t access the

services that reside on the server.

Network Topology

A network topology graphically displays the interconnection methods used

between devices. Topology can be logical or physical. Logical topology

refers to the way that data travels from one device to another and largely

determined by access method. Physical topology refers to the physical

layout of devices and how are they cabled. There are several network

topologies such are:

■Bus.

■Star.

■Ring.

■Mesh.

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Bus Topology

A bus topology, as depicted in Figure, typically uses a cable running

through the area requiring connectivity. Devices that need to connect to the

network then tap into this nearby cable. Early Ethernet networks commonly

relied on bus topologies.

Bus Topology- Advantages and Disadvantages

Advantages:

■It is inexpensive and easy to implement.

■It doesn’t require special equipment.

■It requires less cable than other topologies.

Disadvantages:

■It cannot be expanded easily. Doing so may render the network

inaccessible while the expansion is performed.

■A break in the cable renders the entire segment unusable.

■It is difficult to troubleshoot.

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Star Topology

In star topology every device uses an individual cable to connect to a

central point (Hub or Switch). The star topology is the most popular

physical topology in use today, with a switch at the center of the star and

unshielded twisted-pair cable (UTP) used to connect from the switch ports

to clients.

Star Topology- Advantages and Disadvantages

Advantages:

■It can be easily expanded without disruption to existing systems.

■A cable failure affects only a single system.

■It is easy to troubleshoot.

Disadvantages:

■It requires additional networking equipment and more cables than bus.

■Centralized devices create a single point of failure

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Ring Topology

In ring topology traffic flows in a circular fashion around a closed network

loop (that is, a ring). Typically, a ring topology sends data, in a single

direction, to each connected device in turn, until the intended destination

receives the data.

Ring Topology- Advantages and Disadvantages

Advantages:

■ A dual ring topology adds a layer of fault tolerance.

Disadvantages:

■ A cable network break can disrupt the entire network.

■Also adding or removing computers to the network creates network

disruption for all users.

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Mesh Topology

In Mesh topology each device connects directly to every other device. A

full mesh uses point-to-point connectivity between all devices however a

partial mesh uses point-to-point connectivity between devices, but not all of

them.

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Mesh Topology- Advantages and Disadvantages

Advantages:

■Multiple links provide fault tolerance and redundancy.

■The network can be expanded with minimal or no disruption.

Disadvantages:

■It is difficult to implement.

■It can be expensive.

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Network Categories

Based on the geographic dispersion of network components, networks can

be classified into various categories, including the following:

■ Local-Area Network (LAN)

■ Wide-Area Network (WAN)

■ Campus-Area Network (CAN)

■ Metropolitan-Area Network (MAN)

■ Personal-Area Network (PAN)

Local Area Network (LAN)

A LAN interconnects network components within a local region (for

example, within a building). Examples of common LAN technologies are

Ethernet and wireless LAN networks.

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Wide Area Network (WAN)

A WAN interconnects network components that are geographically

separated. For example, a corporate headquarters might have multiple

WAN connections to remote office sites. Asynchronous Transfer Mode

(ATM), and Frame Relay are examples of WAN technologies.

Metropolitan Area Network (MAN)

A MAN is confined to a certain geographic area, such as a city. A MAN is

almost always bigger than a LAN and usually smaller than or equal to a

WAN. Metro Ethernet is an example of a MAN technology.

Campus Area Network (CAN)

A CAN is a network that spans a defined single location (such as an office

complex with multiple buildings or a college campus) but is not large

enough to be considered a MAN. Metro Ethernet is an example of a MAN

technology.

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Personal Area Network (PAN)

A PAN is a network whose scale is even smaller than a LAN. As an

example, a connection between a PC and a digital camera via a universal

serial bus (USB) cable could be considered a PAN. A PAN, could be a

wireless connection. Bluetooth connection between your cell phone and

your car’s audio system is considered a wireless PAN (WPAN).

The main distinction of a PAN, however, is that its range is typically

limited to just a few meters.

Network Infrastructure Devices

Computers and printers within a network are connected to various network

devices such as: -

■Hub.

■Switch.

■Router.

■Access point.

■Bridge.

Hubs

Hub is a simple connection network device & has no intelligence. a hub

does not make forwarding decisions. Instead, a hub receives bits in on one

port and then retransmits those bits out all other ports. Hub can operate in

half-duplex mode. data can be either sent or received on the wire but not at

the same time.

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The two basic types of Ethernet hubs are as follows:

■ Passive hub: Does not amplify (that is, electrically regenerate) received

bits.

■ Active hub: Regenerates incoming bits as they are sent out all the ports

on a hub, other than the port on which the bits were received.

Switches

Switches are intelligence devices and faster than hub. They can identify

which device is connected to each physical port, based on the Media

Access Control (MAC) address. Switch can operate in both half-duplex

and full-duplex mode. Switch provides better performance & adds some

security.

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Routers

Router is an intelligence device used to connect networks. they use the IP

address to determine the best path.

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Bridge

A bridge joins two or more LAN segments, typically two Ethernet LAN

segments. An Ethernet bridge can be used to scale Ethernet networks to a

larger number of attached devices.

Access Points

A wireless access point (WAP) is sometimes referred to as simply an access

point. Access points provide access to wired networks for wireless clients.

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Open System Interconnection (OSI) Reference Model

OSI model is a framework for network communication. It defines how data

is handled at several different layers. The ISO created and it includes seven

layers with specific activities, protocols, and devices working on each. One

of the primary goals of the OSI Model is operating system independence.

The OSI reference model has the following seven layers:

Application layer (layer 7)

Presentation layer (layer 6)

Session layer (layer 5)

Transport layer (layer 4)

Network layer (layer 3)

Data Link layer (layer 2)

Physical layer (layer 1)

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At the physical layer, a series of 1s and 0s represent data. At upper layers,

however, bits are grouped together, into what is known as a protocol data

unit (PDU) or a data service unit.

Application Layer

Application layer provides an interface for users to interact with application

service or networking service such Web browser, Telnet etc. Several

protocols operate on the Application layer. such AS HTTP, FTP, DNS and

DHCP.

Presentation Layer

Determines how to format and present the data.

Major functions of Presentation Layer:

-Encoding & Decoding using ASCII, EBCDIC.

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-Encryption & Decryption.

-Compression & Decompression.

Session Layer

Responsible for establishing, maintaining, and terminating sessions.

A session is simply a lasting connection between two networking devices.

Two network protocols that operate on this layer are the Network Basic

Input/output System (NetBIOS) and Remote Procedure Call (RPC).

Transport Layer

It is responsible for transporting data. this layer divides data into smaller

chunks called segments and then reassembles the received data.

Major Functions: -.

Segmentation.

Sequencing & Reassembling.

Error Correction & Flow Control.

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Transport Layer –Protocols

TCP UDP

Transmission Control Protocol User Datagram Protocol

Connection oriented Connection less

Supports ACK No Supports for ACK

Reliable communication Unreliable communication

Slower data transmission Faster data transmission

Eg: HTTP , FTP , SMTP Eg: DNS, DHCP, TFTP

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Network Layer

The Network layer is responsible for determining the best route to a

destination. It uses routing protocols to build routing tables and uses

Internet Protocol (IP) as the routed protocol. IP addresses are used at this

layer to ensure the data can get to its destination. Data traveling on the

Network layer is referred to as packets. The device that works at network

layer is called Router.

Data Link Layer

The Data Link layer is concerned with data delivery on a local area network

(LAN). Data traveling on the Data Link layer is referred to as frames.

Media Access Control (MAC) defines how packets are placed onto the

physical media at the Physical layer. The MAC address is also called a

physical address, hardware address, burned-in address, or Ethernet address.

Physical devices operating on the Data Link layer include bridges,

switches, and NICs.

Physical Layer

The Physical layer defines the physical specifications of the network, such

as cables and connectors. Data traveling on the Physical layer is converted

to bits, or ones and zeros (such as 110011010101). Devices that work at

physical layer are hubs and repeaters.

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Transmission Control Protocol/ Internet Protocol (TCP/ IP)

Reference Model

The TCP/IP Model is a four-layer model created in the 1970s by the U.S.

Department of Defense (DoD). The TCP/IP Model works similarly to the

OSI Model.

The TCP/IP model is basically a condensed version of the OSI model that

comprises four instead of seven layers:

Process/Application layer

Host-to-Host layer/or Transport

Internet layer

Network Access layer/or Link

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TCP/IP Model Layers and Protocols

Application Layer: Protocols on this layer are used by applications to

access network resources. Protocols include DNS, HTTP, FTP, SMTP,

POP3, IMAP4, and SNMP.

Transport Layer: Protocols on this layer control data transfer on the

network by managing sessions between devices. The two primary protocols

are TCP and UDP. It is also known as the host-to-host layer.

Internet Layer: Protocols on the Internet layer control the movement and

routing of packets between networks. Protocols on this layer include IPv4,

IPv6, IGMP, ICMP, and ARP.

Link Layer: This layer defines how data is transmitted onto the media. It

includes multiple protocols such as Ethernet, token ring, frame relay, and

ATM.The Link layer is also known as the Network Interface or Network

Access layer.

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Data Encapsulation

When a host transmits data across a network to another device, the data

goes through a process called encapsulation and is wrapped with protocol

information at each layer of the OSI model. Each layer communicates only

with its peer layer on the receiving device.

To communicate and exchange information, each layer uses protocol data

units (PDUs). These hold the control information attached to the data at

each layer of the model. They are usually attached to the header in front of

the data field but can also be at the trailer, or end, of it. Each PDU attaches

to the data by encapsulating it at each layer of the OSI model, and each has

a specific name depending on the information provided in each header. This

PDU information is read-only by the peer layer on the receiving device.

After its read, it’s stripped off and the data is then handed to the next layer

up.

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Binary, Hexadecimal and Decimal Numbering System

Binary System: The digits used are limited to either a 1 or a 0, and each

digit is called a bit, which is short for binary digit.

Typically, you group either 4 or 8 bits together, with these being referred to

as a nibble and a byte, respectively.

Decimal System: is a numbering system that we use in daily life. In a Base-

10 numbering system, there are ten digits, in the range of 0 through 9.

Converting a Binary Number to a Decimal Number

To convert a binary number to a decimal number, you populate the binary

table with the given binary digits. Then you add up the column heading

values for those columns containing a 1.

For example, consider table below. Only the 128, 16, 4, and 2 columns

contain a 1, and all the other columns contain a 0. If you add all the column

headings containing a 1 in their column (that is, 128 + 16 + 4 + 2), you get

a result of 150. Therefore, you can conclude that the binary number of

10010110 equates to a decimal value of 150.

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Converting a Decimal Number to a Binary Number

To convert numbers from decimal to binary, staring with the leftmost

column, ask the question, ―Is this number equal to or greater than the

column heading?‖ If the answer to that question is no, place a 0 in that

column and move to the next column. If the answer is yes, place a 1 in that

column and subtract the value of the column heading from the number you

are converting. When you then move to the next column (to your right),

again ask yourself, ―Is this number (which is the result of your previous

subtraction) equal to or greater than the column heading?‖ This process

continues (to the right) for all the remaining column headings.

For example, imagine that you want to convert the number 167 to binary.

You can now conclude that a decimal number of 167 equates to a binary

value of 10100111. In fact, you can check your work by adding up the

values for the column headings that contain a 1 in their column. In this

example, the 128, 32, 4, 2, and 1 columns contain a 1. If you add these

values, the result is 167 (that is, 128 + 32 + 4 + 2 + 1 = 167).

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Binary to decimal memorization chart

1000 0000 128

1100 0000 192

1110 0000 224

1111 0000 240

1111 1000 248

1111 1100 252

1111 1110 254

1111 1111 255

Hexadecimal System: is a numbering system that uses the characters 0

through 9. Because the numbers 10, 11, 12, and so on can’t be used

(because they are two-digit numbers), the letters A, B, C, D, E, and F are

used instead to represent 10, 11, 12, 13, 14, and 15, respectively.

Hexadecimal Value Binary Value Decimal Value

0 0000 0

1 0001 1

2 0010 2

3 0011 3

4 0100 4

5 0101 5

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6 0110 6

7 0111 7

8 1000 8

9 1001 9

A 1010 10

B 1011 11

C 1100 12

D 1101 13

E 1110 14

F 1111 15

IPv4 Addressing

An IP address is a numeric identifier assigned to each machine on an IP

network. It designates the specific location of a device on the network.

An IP address is a software address, not a hardware address—the latter is

hard-coded on a network interface card (NIC) and used for finding hosts on

a local network. IP addressing was designed to allow hosts on one network

to communicate with a host on a different network regardless of the type of

LANs the hosts are participating in.

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IPv4 Address Structure

An IPv4 address is a 32-bit address. However, rather than writing out each

individual bit value, the address is typically written in dotted-decimal

notation. Consider the IP address of 10.1.2.3. This address is written in

dotted-decimal notation. Notice that the IP address is divided into four

separate numbers, separated by periods. Each number represents one-fourth

of the IP address. Specifically, each number represents an 8-bit portion of

the 32 bits in the address. Because each of these four divisions of an IP

address represent 8 bits, these divisions are called octets.

Interestingly, an IP address is composed of two types of addresses: a

network address and a host address. Specifically, a group of contiguous

left-justified bits represent the network address, and the remaining bits (that

is, a group of contiguous right-justified bits) represent the address of a host

on a network. The IP address component that determines which bits refer to

the network and which bits refer to the host is called the subnet mask. You

can think of the subnet mask as a dividing line separating an IP addresses

32 bits into a group of network bits (on the left) and a group of host bits (on

the right).

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A subnet mask typically consists of a series of contiguous 1s followed by a

set of continuous 0s. In total, a subnet mask contains 32 bits, which

correspond to the 32 bits found in an IPv4 address. The 1s in a subnet mask

correspond to network bits in an IPv4 address, and 0s in a subnet mask

correspond to host bits in an IPv4 address.

The designers of the Internet decided to create classes of networks based on

network size. For the small number of networks possessing a very large

number of nodes, they created the rank Class A network. At the other

extreme is the Class C network, which is reserved for the numerous

networks with a small number of nodes. The class distinction for medium

size networks is called the Class B.

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Public & Private IP Address

The people who created the IP addressing scheme also created private IP

addresses. These addresses can be used on a private network, but they’re

not routable through the Internet. This is designed for the purpose of

creating a measure of well-needed security, but it also conveniently saves

valuable IP address space.

If every host on every network was required to have real routable IP

addresses, we would have run out of IP addresses to hand out years ago.

But by using private IP addresses, ISPs, corporations, and home users only

need a relatively tiny group of bona fide IP addresses to connect their

networks to the Internet. This is economical because they can use private IP

addresses on their inside networks and get along just fine.

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Network Address & Broadcast Address

Network Address : IP Address with all bits as ZERO in the host portion.

Ex: 10.0.0.0

Broadcast Address: IP Address with all bits as ONES in the host portion.

Ex: 10.255.255.255

Valid IP Addresses lie between the network address and broadcast address.

Only Valid IP addresses are assigned to hosts /clients.

Example 1: IP Address: 10.2.0.0.

IP Address: 10.2.0.0

Class: A

Octet format N.H.H.H

Network Address: 10.0.0.0

Broadcast Address: 10.255.255.255

First Address: 10.0.0.1

Last Address : 10.255.255.254

Host Address: 10.2.0.0

Subnet Mask: 255.0.0.0

Example 2: 192.168.5.24

Class :

Network Address:

Broadcast Address:

First Address:

Last Address :

Host Address:

Subnet Mask:

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Types of Addresses

Data is transmitted to and from hosts on networks using one of three

transmission types:

1-Unicast

Most network traffic is unicast in nature, meaning that traffic travels from a

single source device to a single destination device.

2-Broadcast

Broadcast traffic travels from a single source to all destinations on a

network.

3-Multicast

Multicast technology provides an efficient mechanism for a single host to

send traffic to multiple, yet specific, destinations.

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Subnetting

Creating multiple networks from a single network by converting host bits

into network bits . Subnetting provides better performance and security.

Rules for Subnetting

1-How many subnets? 2x = number of subnets. x is the number of masked

bits, or the 1s. (Given SM –Default SM)

2-How many hosts per subnet? 2y – 2 = number of hosts per subnet. y is the

number of unmasked bits, or the 0s. (32- Given SM ).

3-What are the valid subnets? 256 – subnet mask = block size, Start

counting at zero in blocks size until you reach the subnet mask value.

4-What’s the broadcast address for each subnet? The number right before

the value of the next subnet. (Broadcast = Next Subnet -1 )

5-What are the valid hosts? Valid hosts address are the numbers between

the subnets and broadcasts address . (First Host = Subnet + 1 , and Last

Host = Broadcast -1).

Subnetting Example 1:

Example : IP Address 192.168.1.0/25

Answer:

Network Address:192.168.1.0 , Subnet Mask: 255.255.255.128

Answer for Five Questions:

1. How many subnets? Since 128 is 1 bit on (10000000), the answer

would be 21 = 2. (25-24=1)

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2. How many hosts per subnet? We have 7 host bits off (10000000), so

the equation would be 27 – 2 = 126 hosts. (32-25=7)

3. What are the valid subnets? 256 – 128 = 128. Remember, we’ll start

at zero and count in our block size, so our subnets are 0, 128.

4. What’s the broadcast address for each subnet?. For the zero subnet,

the next subnet is 128, so the broadcast of the 0 subnet is 127.

Broadcast for the last subnet is always 255.

5. What are the valid hosts? These are the numbers between the subnet

and broadcast address.

Subnet 0 128

First Host 1 129

Last Host 126 254

Broadcast 127 255

Subnetting Example 2:

Example : IP Address 192.168.1.0/26

Answer:

Network Address:192.168.1.0 , Subnet Mask: 255.255.255.192

Answer for Five Questions:

1. How many subnets? Since 192 is 2 bits on (11000000), the answer

would be 22 = 4 subnets. (26-24=2)

2. How many hosts per subnet? We have 6 host bits off (11000000), so

the equation would be 26 – 2 = 62 hosts. (32-26=6)

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3. What are the valid subnets? 256 – 192 = 64. start at zero and count in

our block size, so our subnets are 0, 64, 128, and 192.

4. What’s the broadcast address for each subnet? The number right

before the value of the next subnet is all host bits turned on and equals

the broadcast address. For the zero subnet, the next subnet is 64, so

the broadcast address for the zero subnet is 63.

5. What are the valid hosts? These are the numbers between the subnet

and broadcast address.

Subnet 0 64 128 192

First Host 1 65 129 193

Last Host 62 126 190 254

Broadcast 63 127 191 255

Subnetting Example 3:

Example : IP Address 192.168.10.0/27

Answer:

Network address = 192.168.10.0

Subnet mask = 255.255.255.224

Five Questions:

1. How many subnets? 23 = 8.

2. How many hosts per subnet? equation would be 25 – 2 = 30 hosts.

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3. What are the valid subnets? 256 – 224 = 32. We just start at zero and

count to the subnet mask value in blocks (increments) of 32: 0, 32, 64,

96, 128, 160, 192, and 224.

4. What’s the broadcast address for each subnet (always the number

right before the next subnet)?.

5. What are the valid hosts (the numbers between the subnet number and

the broadcast address)?.

Ethernet Networking

The genesis of Ethernet was 1972, when this technology was developed by

Xerox Corporation. The original intent was to create a technology to allow

computers to connect with laser printers.

Ethernet is a contention-based media access method that allows all hosts on

a network to share the same link’s bandwidth. Some reasons it’s so popular

are that Ethernet is really pretty simple to implement and it makes

troubleshooting fairly straightforward as well. Ethernet is so readily

scalable, meaning that it eases the process of integrating new technologies

into an existing network infrastructure, like upgrading from Fast Ethernet

to Gigabit Ethernet. Ethernet uses both Data Link and Physical layer

specifications.

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Carrier Sense Multiple Access Collision Detect (CSMA/CD)

Ethernet networking uses a protocol called Carrier Sense Multiple Access

with Collision Detection (CSMA/CD), which helps devices share the

bandwidth evenly while preventing two devices from transmitting

simultaneously on the same network medium. CSMA/CD was actually

created to overcome the problem of the collisions that occur when packets

are transmitted from different nodes at the same time.

When a collision occurs on an Ethernet LAN, the following happens:

1. A jam signal informs all devices that a collision occurred.

2. The collision invokes a random backoff algorithm.

3. Each device on the Ethernet segment stops transmitting for a short time

until its backoff timer expires.

4. All hosts have equal priority to transmit after the timers have expired.

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Half-Duplex and Full-Duplex Ethernet

Half-Duplex: Data can be sent both ways but only one way at a time. The

Ethtent hub can work in Half-Duplex speed mode.

Full-Duplex: In full-duplex mode a device can simultaneously send and

receive at the same time. The Ethenet switch can work in both Half-Duplex

and Full-Duplex modes.

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Current Ethernet Tehcnology

Table below offers a listing of multiple Ethernet standards, along with their

media type, bandwidth capacity, and distance limitation.

Ethernet Cabling

There are 3 types of cableing confiuuration used in Ethernet networks:

Straight-through cable

Crossover cable

Rolled cable

Straight-through Cable

The straight-through cable is used to connect the following devices:

Host to switch or hub

Router to switch or hub

Four wires are used in straight-through cable to connect Ethernet devices.

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Crossover Cable

The crossover cable can be used to connect the following devices:

Switch to switch

Hub to hub

Host to host

Hub to switch

Router direct to host

Router to router

The same four wires used in the straight-through cable are used in this

cable—we just connect different pins together.

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Rolled Cable

Rolled Ethernet cable is used to connect a host EIA-TIA 232 interface to a

router or a switch console serial communication (COM) port.

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Introduction to Cisco IOS

The Cisco Internetworking Operating System (IOS) is a proprietary

operating system that provides routing, switching, internetworking, and

telecommunications features. It runs on most Cisco routers as well as Cisco

switches.

You can access the Cisco IOS through the console port of a router, from a

modem into the auxiliary (or aux) port, or even through Telnet and Secure

Shell (SSH). Access to the IOS command line is called an exec session.

Setup Mode

If the router has no initial configuration, you will be prompted to use setup

mode to establish an initial configuration. You can also enter setup mode at

any time from the command line by typing the command setup from

something called privileged mode. Setup mode covers only some global

commands and is generally just not helpful. Here is an example:

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Command-line Interface (CLI) Mode

Setup provides a minimum amount of configuration in an easy format for

someone who does not understand how to configure a Cisco router from the

command line. You always use the command-line interface (CLI) to

configure cisco routers or switches by issuing commands.

One key to navigating the CLI is to always be aware of which router

configuration mode you are currently in .You can tell which configuration

mode you are in by watching the CLI prompt.

Mode Definition Example

User EXEC mode Limited to basic monitoring

commands Router>

Privileged EXEC mode Provides access to all other

router commands Router#

Global configuration

mode

Commands that affect the

entire system Router(config)#

Once you understand the different modes, you will need to be able to move

from one mode to another within the CLI. The commands in table bloew

allow you to navigate between the assorted CLI modes:

Command Meaning

Router>enable Changes from user EXEC to privileged

EXEC mode

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Router#disable Changes to user EXEC from privileged

EXEC mode

Router#config term Changes to global configuration mode from

privileged mode

Router(config)#exit Exits from any configuration mode to

privileged mode

Router(config)#interface Enters interface configuration mode from

global configuration mode

Editing and Help Features

The CLI also provides extensive Editing and online help as shown in the

table below.

Command Meaning

Ctrl+P or Up arrow Shows last command entered

Ctrl+N or Down arrow Shows previous commands entered

Ctrl+Z Ends configuration mode

Tab Finishes typing a command for you

Router#? Shows all available commands

Router#c? Shows all available commands beginning

with the letter c

Router#clock ? Shows all available options for the clock

command

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The Internal Components of a Cisco Router and Switch

ROM

-contains bootstrap program which searches & loads the OS.

-It is similar to BIOS of PC.

Flash RAM

-stores the Internetworking Operating System (IOS).

NVRAM

-It is similar to hard disk & stores the startup configuration.

RAM

-It is called main memory & stores the running configuration.

Configuring a Router Using CLI

A brand new router doesn't have any configuration so initial configuration

has to be done first. The following configuration needs to be done:

Hostname.

IP address.

Passwords:

1-Console.

2-VTY (Telnet).

3-Enable or Secret.

Save the configurations.

Configuring Router’s Hostname

You can set the identity of the router with the hostname command. This is

only locally significant, which means it has no bearing on how the router

performs name lookups or works on the internetwork.

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To configure the host name of the router, run the following commands:

Router>enable

Router#configure terminal

Router(config)#hostname HawlerRouter

HawlerRouter(config)#exit

HawlerRouter(config)#

Configuring Router interfaces

Interface configuration is one of the most important router configurations,

because without interfaces, a router is pretty much a completely useless

object. Plus, interface configurations must be totally precise to enable

communication with other devices. Network layer addresses, media type,

bandwidth, and other administrator commands are all used to configure an

interface.

To configure IP address to LAN interfaces , run the commands:

HawlerRouter >enable

HawlerRouter #configure terminal

HawlerRouter (config)#interface fastethernet 0/0

HawlerRouter (config-if)#ip address 10.0.0.1 255.0.0.0

HawlerRouter (config-if)#no shutdown

HawlerRouter (config-if)#exit

HawlerRouter (config)#exit

HawlerRouter #

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Configuring Router’s Passwords

There are four passwords you’ll need to secure your Cisco routers:

console, telnet (VTY), enable password, and enable secret. The enable

secret and enable password are the ones used to set the password for

securing privileged mode. Once the enable commands are set, users will be

prompted for a password. The other three are used to configure a password

when user mode is accessed through the console port, through the auxiliary

port, or via Telnet.

To configure an encrypted privileged password, run the following

commands:

HawlerRouter >enable

HawlerRouter #configure terminal

HawlerRouter (config)#enable secret @MyRouterPass

HawlerRouter (config)#exit

HawlerRouter #

To configure the console password, run the following commands:

HawlerRouter >enable

HawlerRouter #configure terminal

HawlerRouter (config)#line console 0

HawlerRouter (config-line)#password @Kani$2016

HawlerRouter (config-line)#login

HawlerRouter (config-line)#exit

HawlerRouter (config)#exit

HawlerRouter #

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To configure a password for the VTY lines, run the following commands:

HawlerRouter >enable

HawlerRouter #configure terminal

HawlerRouter (config-line)#line vty 0 4

HawlerRouter (config-line)#password @Kani#2015

HawlerRouter (config-line)#login

HawlerRouter (config-line)#exit

HawlerRouter (config)#exit

HawlerRouter #

Viewing, Saving, and Erasing Configurations

Once you have gone to all the work of creating a configuration, you will

need to know how to save it, and maybe even delete configuration.

Command Meaning

Router#copy run startup Saves the running configuration to NVRAM

Router#show run Shows the running configuration

Router#show startup Shows the start-up configuration

Router#erase startup Erases the configuration stored in NVRAM

Router#reload Restart the router

Router#show ip interface shows the IP configuration on all interfaces.

Router#show ip interface

brief

This command provides a quick overview of

the router’s interfaces, including the logical

address and status.

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Routing Process

The process of moving packets from one network to another network using

routers.Routers by defualt know only directly connected networks and

indirectly connected network must be added to the router either manually

by hand (statically) or dynmiacaly via routing protocols.

Types of Routing

1. Static Routing.

2. Dynamic Routing.

Static Routing

In static routing routes for each destination network has to be manually

configured by the administrator. Static routing requires destination network

ID for configuration therefore used in small network.

Dynamic Routing

protocols are used to find networks and update routing tables on routers so

it requires directly connected network IDs for configuration. dynmiac

routing used in medium and large network.