Computer Networks CCNA 1 & 2 - Weebly Networks CCNA 1 & 2 3rd Stage Academic Year 2016-2017 Lecturer...
Transcript of Computer Networks CCNA 1 & 2 - Weebly Networks CCNA 1 & 2 3rd Stage Academic Year 2016-2017 Lecturer...
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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.