4. Data Networks
Sharing data through the use of floppy disks is not an efficient or
cost-effective manner in which to operate businesses.
Businesses needed a solution that would successfully address the
following three problems:
• How to avoid duplication of equipment and resources
• How to communicate efficiently
• How to set up and manage a network
Businesses realized that networking technology could increase
productivity while saving money.
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5. Networking Devices
Equipment that connects directly to a network segment is referred
to as a device.
These devices are broken up into two classifications.
• end-user devices
• network devices
End-user devices include computers, printers, scanners, and other
devices that provide services directly to the user.
Network devices include all the devices that connect the end-user
devices together to allow them to communicate.
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6. Network Interface Card
A network interface card (NIC) is a printed circuit board that
provides network communication capabilities to and from a
personal computer. Also called a LAN adapter.
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8. Cisco Icons and Symbols
Router Wireless Secure Router Firewall Home Office
Router
Workgroup Access Point IP Phone Mobile Small
Switch Access Business
Phone
Wireless Line: Serial Line: Ethernet
Connectivity
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9. Repeater
A repeater is a network device used to regenerate a signal.
Repeaters regenerate analog or digital signals distorted by
transmission loss due to attenuation. A repeater does not perform
intelligent routing.
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10. Hub
Hubs concentrate connections.
In other words, they take a
group of hosts and allow the
network to see them as a single
unit.
This is done passively, without
any other effect on the data
transmission.
Active hubs not only
concentrate hosts, but they
also regenerate signals.
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11. Bridge
Bridges convert network transmission data formats as well as
perform basic data transmission management. Bridges, as the
name implies, provide connections between LANs. Not only do
bridges connect LANs, but they also perform a check on the data to
determine whether it should cross the bridge or not. This makes
each part of the network more efficient.
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12. Workgroup Switch
Workgroup switches add more
intelligence to data transfer
management.
Switches can determine
whether data should remain
on a LAN or not, and they can
transfer the data to the
connection that needs that
data.
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13. Router
Routers have all capabilities of the previous devices. Routers can
regenerate signals, concentrate multiple connections, convert data
transmission formats, and manage data transfers.They can also
connect to a WAN, which allows them to connect LANs that are
separated by great distances.
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14. “The Cloud”
The cloud is used in diagrams to represent where the connection to
the internet is.
It also represents all of the devices on the internet.
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15. Network Topologies
Network topology defines the structure of the network.
One part of the topology definition is the physical topology, which is
the actual layout of the wire or media.
The other part is the logical topology,which defines how the media
is accessed by the hosts for sending data.
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17. Bus Topology
A bus topology uses a single backbone cable that is terminated at
both ends.
All the hosts connect directly to this backbone.
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18. Ring Topology
A ring topology connects one host to the next and the last host to
the first.
This creates a physical ring of cable.
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19. Star Topology
A star topology connects all cables to a central point of
concentration.
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20. Extended Star Topology
An extended star topology links individual stars together by
connecting the hubs and/or switches.This topology can extend the
scope and coverage of the network.
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22. Mesh Topology
A mesh topology is implemented to provide as much
protection as possible from interruption of service.
Each host has its own connections to all other hosts. Although
the Internet has multiple paths to any one location, it does
not adopt the full mesh topology.
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23. LANs, MANs, & WANs
One early solution was the creation of local-area network (LAN)
standards which provided an open set of guidelines for creating
network hardware and software, making equipment from different
companies compatible.
What was needed was a way for information to move efficiently and
quickly, not only within a company, but also from one business to
another.
The solution was the creation of metropolitan-area networks
(MANs) and wide-area networks (WANs).
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28. SANs
A SAN is a dedicated, high-
performance network used to
move data between servers and
storage resources.
Because it is a separate,
dedicated network, it avoids any
traffic conflict between clients
and servers.
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29. Virtual Private Network
A VPN is a private network that is constructed within a public network
infrastructure such as the global Internet. Using VPN, a telecommuter can
access the network of the company headquarters through the Internet by
building a secure tunnel between the telecommuter’s PC and a VPN router in
the headquarters.
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33. Understanding Host-to-Host
Communications
– Older model
• Proprietary
• Application and combinations software controlled by one
vendor
– Standards-based model
• Multivendor software
• Layered approach
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34. Why do we need the OSI Model?
To address the problem of networks increasing in size and
in number, the International Organization for
Standardization (ISO) researched many network schemes
and recognized that there was a need to create a network
model that would help network builders implement
networks that could communicate and work together and
therefore, released the OSI reference model in 1984.
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35. OSI Model
Reduces complexity
Standardizes interfaces
Ensures interoperable technology
Accelerates evolution
Simplifies teaching and learning
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36. Don’t Get Confused.
ISO - International Organization for Standardization
OSI - Open System Interconnection
IOS - Internetwork Operating System
The ISO created the OSI to make the IOS more efficient.
The “ISO” acronym is correct as shown.
To avoid confusion, some people say “International
Standard Organization.”
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37. The OSI Reference Model
7 Application The OSI Model will be used
throughout your entire
6 Presentation
networking career!
5 Session
4 Transport
3 Network
Memorize it!
2 Data Link
1 Physical
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38. Layer 7 - The Application Layer
7 Application This layer deal with
networking applications.
6 Presentation
5 Session Examples:
4 Transport Email
Web browsers
3 Network
2 Data Link PDU - Data
1 Physical
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39. Layer 6 - The Presentation Layer
7 Application This layer is responsible for
presenting the data in the
6 Presentation
required format which may
5 Session include:
4 Transport Encryption
Compression
3 Network
2 Data Link PDU - Data
1 Physical
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40. Layer 5 - The Session Layer
7 Application This layer establishes, manages,
and terminates sessions
6 Presentation
between two communicating
5 Session hosts.
4 Transport
3 Network PDU - Data
2 Data Link
1 Physical
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41. Layer 4 - The Transport Layer
7 Application This layer breaks up the data
from the sending host and then
6 Presentation
reassembles it in the receiver.
5 Session
4 Transport It also is used to insure reliable
data transport across the
3 Network network. Also provide error
2 Data Link correction.
1 Physical
PDU - Segments
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42. Layer 3 - The Network Layer
7 Application
Makes “Best Path
6 Presentation
Determination” decisions based
5 Session on logical addresses (usually IP
4 Transport addresses).
3 Network PDU - Packets
2 Data Link
1 Physical
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43. Layer 2 - The Data Link Layer
7 Application This layer provides reliable
transit of data across a physical
6 Presentation
link “error detection”.
5 Session
4 Transport Makes decisions based on
physical addresses (usually MAC
3 Network addresses).
2 Data Link
PDU - Frames
1 Physical
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44. Layer 1 - The Physical Layer
This is the physical media
7 Application through which the data,
6 Presentation represented as electronic signals,
is sent from the source host to
5 Session
the destination host.
4 Transport
3 Network
PDU - Bits
2 Data Link
1 Physical
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45. Host Layers
7 Application These layers only
exist in the source
6 Presentation
and destination
5 Session host computers.
4 Transport
3 Network
2 Data Link
1 Physical
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46. Media Layers
7 Application
6 Presentation
5 Session
4 Transport
These layers manage the
3 Network
information out in the
2 Data Link LAN or WAN between the
1 Physical source and destination
hosts.
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52. Cabling the Campus
Core_
Server
core_sw_a
Leased Line/
ISDN Cloud Frame Relay
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53. Unshielded Twisted-Pair Cable
– Speed and throughput: 10 to 1000 Mb/s
– Average cost per node: Least expensive
– Media and connector size: Small
– Maximum cable length: Varies
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58. Ethernet Standards
The Ethernet standard specifies that each of the pins on an RJ-45
connector have a particular purpose. A NIC transmits signals on
pins 1 & 2, and it receives signals on pins 3 & 6.
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59. Remember…
A straight cable has T568B or T568A on both ends. A crossover (or cross-
connect) cable has T568B on one end and T568A on the other. A console
cable had T568B on one end and reverse T568B on the other, which is
why it is also called a rollover cable.
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65. Fiber Optic Connectors
Connectors are attached to the fiber ends so that the fibers can be
connected to the ports on the transmitter and receiver.
The type of connector most commonly used with multimode fiber is
the Subscriber Connector (SC connector).On single-mode fiber, the
Straight Tip (ST) connector is frequently used
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66. Cable Specifications
10BASE-T
The T stands for twisted pair.
10BASE5
The 5 represents the fact that a signal can travel for approximately 500
meters 10BASE5 is often referred to as Thicknet.
10BASE2
The 2 represents the fact that a signal can travel for approximately 200
meters 10BASE2 is often referred to as Thinnet.
All 3 of these specifications refer to the speed of transmission at 10 Mbps
and a type of transmission that is baseband, or digitally interpreted. Thinnet
and Thicknet are actually a type of networks, while 10BASE2 & 10BASE5 are
the types of cabling used in these networks.
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71. Serial Implementation of DTE & DCE
When connecting directly to a service provider, or to a device
such as a CSU/DSU that will perform signal clocking, the router is
a DTE and needs a DTE serial cable.
This is typically the case for routers.
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72. Back-to-Back Serial Connection
When performing
a back-to-back
router scenario in
a test
environment, one
of the routers will
be a DTE and the
other will be a
DCE.
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73. Repeater
A repeater is a network device used to regenerate a signal.
Repeaters regenerate analog or digital signals distorted by
transmission loss due to attenuation.Repeater is a Physical Layer
device
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74. The 4 Repeater Rule
The Four Repeater Rule for 10-Mbps Ethernet should be used as a
standard when extending LAN segments.
This rule states that no more than four repeaters can be
used between hosts on a LAN.
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75. Hub
Hubs concentrate
connections.In other words,
they take a group of hosts and
allow the network to see them
as a single unit.
Hub is a physical layer device.
All devices in the same collision domain.
All devices in the same broadcast domain.
Devices share the same bandwidth.
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76. Network Interface Card
The function of a NIC is to connect a host device to the network medium.
A NIC is a printed circuit board that fits into the expansion slot on the motherboard or
peripheral device of a computer. The NIC is also referred to as a network adapter.
NICs are considered Data Link Layer devices because each NIC carries a unique code called a
MAC address.
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77. MAC Address
MAC address is 48 bits in length and expressed as twelve hexadecimal
digits.MAC addresses are sometimes referred to as burned-in addresses (BIA)
because they are burned into read-only memory (ROM)
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78. Bridge
Bridges are Data Link layer devices.Connected host
addresses are learned and stored on a MAC address
table.Each bridge port has a unique MAC address
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81. Switch
Switches are Data Link layer
devices.
Each Switch port has a unique
MAC address.
Connected host MAC
addresses are learned and
stored on a MAC address
table.
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82. • No. of broadcast domain=No. of router interfaces
• Switches create separate collision domains but a single broadcast domain.
Routers provide a separate broadcast domain for each interface.
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83. Hub: One collision domain, one broadcast domain
Bridge: Two collision domains, one broadcast domain
Switch: Four collision domains, one broadcast domain
Router: Three collision domains, three broadcast domains
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84. Switching Modes
cut-through
A switch starts to transfer the frame as soon as the destination MAC address is
received. No error checking is available.
store-and-forward
The switch can receive the entire frame before sending it out the destination
port. This gives the switch software an opportunity to verify the Frame Check
Sum (FCS) to ensure that the frame was reliably received before sending it to the
destination.
fragment-free
A compromise between the cut-through and store-and-forward modes.
Fragment-free reads the first 64 bytes, which includes the frame header, and
switching begins before the entire data field and checksum are read.
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85. Full Duplex
Another capability emerges when only two nodes are connected. In a network that uses
twisted-pair cabling, one pair is used to carry the transmitted signal from one node to the
other node. A separate pair is used for the return or received signal. It is possible for signals
to pass through both pairs simultaneously. The capability of communication in both
directions at once is known as full duplex.
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87. Peer-to-Peer Network
In a peer-to-peer network, networked computers act as equal partners, or peers.
As peers, each computer can take on the client function or the server function.
At one time, computer A may make a request for a file from computer B, which responds
by serving the file to computer A. Computer A functions as client, while B functions as the
server. At a later time, computers A and B can reverse roles.
In a peer-to-peer network, individual users control their own resources. Peer-to-peer
networks are relatively easy to install and operate. As networks grow, peer-to-peer
relationships become increasingly difficult to coordinate.
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88. Client/Server Network
In a client/server arrangement, network services are located on a dedicated computer
called a server.
The server responds to the requests of clients.
The server is a central computer that is continuously available to respond to requests from
clients for file, print, application, and other services.
Most network operating systems adopt the form of a client/server relationship.
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90. Why Another Model?
Although the OSI reference model is universally
recognized, the historical and technical open standard
of the Internet is Transmission Control Protocol /
Internet Protocol (TCP/IP).
The TCP/IP reference model and the TCP/IP protocol
stack make data communication possible between any
two computers, anywhere in the world, at nearly the
speed of light.
The U.S. Department of Defense (DoD) created the
TCP/IP reference model.
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91. Don’t Confuse the Models
7 Application
6 Presentation Application
5 Session
4 Transport Transport
3 Network Internet
2 Data Link Network
1 Physical Access
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92. 2 Models
Side-By-Side
7 Application
6 Presentation Application
5 Session
4 Transport Transport
3 Network Internet
2 Data Link Network
1 Physical Access
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93. The Application Layer
The application
layer of the
TCP/IP model
handles high-
level protocols,
issues of
representation,
encoding, and
dialog control.
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94. The Transport Layer
The transport layer provides transport services from
the source host to the destination host. It constitutes
a logical connection between these endpoints of the
network. Transport protocols segment and
reassemble upper-layer applications into the same
data stream between endpoints.
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95. The Internet Layer
The purpose of the Internet layer is to
select the best path through the network for
packets to travel. The main protocol that
functions at this layer is the Internet
Protocol (IP). Best path determination and
packet switching occur at this layer.
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96. The Network Access Layer
It the layer that is concerned with all of the issues that an
IP packet requires to actually make a physical link to the
network media. It includes LAN and WAN details, and all
the details contained in the OSI physical and data-link
layers. NOTE: ARP & RARP work at both the Internet and
Network Access Layers.
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97. Introduction to the Transport Layer
The primary duties of the transport layer, Layer 4 of the OSI
model, are to transport and regulate the flow of information from
the source to the destination, reliably and accurately.
End-to-end control and reliability are provided by sliding
windows, sequencing numbers, and acknowledgments.
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98. More on The Transport Layer
The transport layer provides transport services from the
source host to the destination host.
It establishes a logical connection between the endpoints of
the network.
Transport services include the following basic services:
• Segmentation of upper-layer application data
• Transport of segments from one end host to another
end host
• Flow control provided by sliding windows
• Reliability provided by sequence numbers and
acknowledgments
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99. Flow Control
As the transport layer sends data segments, it tries to ensure that data is not lost.
A receiving host that is unable to process data as quickly as it arrives could be a
cause of data loss.
Flow control avoids the problem of a transmitting host overflowing the buffers in
the receiving host.
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100. TCP
Transmission Control Protocol (TCP) is a connection-oriented Layer 4
protocol that provides reliable full-duplex data transmission.
TCP is part of the TCP/IP protocol stack. In a connection-oriented
environment, a connection is established between both ends before the
transfer of information can begin.
TCP is responsible for breaking messages into segments, reassembling
them at the destination station, resending anything that is not received,
and reassembling messages from the segments.TCP supplies a virtual
circuit between end-user applications.
The protocols that use TCP include:
• FTP (File Transfer Protocol)
• HTTP (Hypertext Transfer Protocol)
• SMTP (Simple Mail Transfer Protocol)
• Telnet Mohannad Al-Hanahnah
102. UDP
User Datagram Protocol (UDP) is the connectionless transport protocol
in the TCP/IP protocol stack.
UDP is a simple protocol that exchanges datagrams, without
acknowledgments or guaranteed delivery. Error processing and
retransmission must be handled by higher layer protocols.
UDP uses no windowing or acknowledgments so reliability, if needed, is
provided by application layer protocols. UDP is designed for applications
that do not need to put sequences of segments together.
The protocols that use UDP include:
• TFTP (Trivial File Transfer Protocol)
• SNMP (Simple Network Management Protocol)
• DHCP (Dynamic Host Control Protocol)
• DNS (Domain Name System)
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104. Well Known Port Numbers
The following port numbers should be memorized:
NOTE:
The curriculum forgot to mention one of the most important port numbers.
Port 80 is used for HTTP or WWW protocols. (Essentially access to the internet.)
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105. 3-Way Handshake
TCP requires connection establishment before data transfer begins.
For a connection to be established or initialized, the two hosts must
synchronize their Initial Sequence Numbers (ISNs).
CTL = Which control bits in the TCP header
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106. Basic Windowing
Data packets must be
delivered to the
recipient in the same
order in which they
were transmitted to
have a reliable,
connection-oriented
data transfer.
The protocol fails if
any data packets are
lost, damaged,
duplicated, or
received in a different
order.
An easy solution is to
have a recipient
acknowledge the
receipt of each packet
before the next
packet is sent.
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110. Decimal vs. Binary Numbers
– Decimal numbers are represented by the numbers
0 through 9.
– Binary numbers are represented by a series of 1s
and 0s.
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116. Why IP Addresses?
– They uniquely identify each device on an IP
network.
– Every host (computer, networking device,
peripheral) must have a unique address.
117. Network Layer Communication Path
A router forwards packets from the originating network to the
destination network using the IP protocol. The packets must
include an identifier for both the source and destination networks.
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119. Network and Host Division
Each complete 32-bit IP address is broken down into a network part
and a host part. A bit or bit sequence at the start of each address
determines the class of the address. There are 5 IP address classes.
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121. IP Address Ranges
The graphic below shows the IP address range of the first octet
both in decimal and binary for each IP address class.
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125. Public IP Addresses
Unique addresses are required for each device on a network.
The Internet Assigned Numbers Authority (IANA).
No two machines that connect to a public network can have the same IP
address because public IP addresses are global and standardized.
All machines connected to the Internet agree to conform to the system.
Public IP addresses must be obtained from an Internet service provider
(ISP) or a registry at some expense.
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126. Private IP Addresses
Private IP addresses are another solution to the problem of the
impending exhaustion of public IP addresses.As mentioned, public
networks require hosts to have unique IP addresses.
However, private networks that are not connected to the Internet may
use any host addresses, as long as each host within the private
network is unique.
Class Private Address Range
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
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129. Network/Broadcast Addresses
at the Binary Level
An IP address that has binary 0s in all host bit positions is
reserved for the network address, which identifies the network.
An IP address that has binary 1s in all host bit positions is
reserved for the broadcast address, which is used to send data
to all hosts on the network. Here are some examples:
Class Network Address Broadcast Address
A 100.0.0.0 100.255.255.255
B 150.75.0.0 150.75.255.255
C 200.100.50.0Mohannad Al-Hanahnah 200.100.50.255
133. HOW WILL YOU FIND
How many bits are NETWORK portion ?
How many bits are HOST portion ?
Solution : Using Network Prefix or Subnet
Mask . . .
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134. Subnet mask
Subnet Mask is another common method used
to identify the network portion and host portion
of an IP address.
In a subnet mask, All network bits = 1
All host bits = 0
For example, 172.16.4.0
the subnet mask = 255.255.0.0
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136. Network Prefixes
A Network Prefix is a method to identify the network
portion and host portion of an IP address.
The prefix length is nothing but the number of
network bits in the IP address.
For example, in 192.168.1.0 /24, the number 24 is no.
of network bits.
the subnet mask = 255.255.255.0
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137. How to find the Network address when a Host IP and Subnet mask
is given …
Any IPv4 Network
address Address
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138. AND ing the Host IP and Subnet mask to get Network Address
0
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140. Introduction to Subnetting
Subnetting a network means to use the subnet mask to divide the
network and break a large network up into smaller, more efficient and
manageable segments, or subnets.
With subnetting, the network is not limited to the default Class A, B, or
C network masks and there is more flexibility in the network design.
Subnet addresses include the network portion, plus a subnet field and
a host field.The ability to decide how to divide the original host portion
into the new subnet and host fields provides addressing flexibility for
the network administrator.
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141. Subnetting Review
• To identify subnets, you will “borrow” bits from the host ID
portion of the IP address:
– The number of subnets available depends on the number
of bits borrowed.
• The available number of subnets = 2s, I which s is the
number of bits borrowed.
– The number of hosts per subnet available depends upon
the number of host ID bits not borrowed.
• The available number of hosts per subnet = 2h -2, in
which h is the number of host bits not borrowed.
• One address is reserved as the network address.
• One address is reserved as the broadcast address.
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145. To create a subnet follow these steps:
1.Determine the number of required network IDs:
One for each subnet
2.Determine the number of required host IDs per subnet:
One for each host
One for each router interface
3.Based on the above requirements, create the following:
One subnet mask for your entire network
A unique subnet ID for each physical segment
A range of host IDs for each subnet
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146. In a Class C address, only 8 bits are available for defining the hosts. Remember
that subnet bits start at the left and go to the right, without skipping bits. This
means that the only Class C subnet masks can be the following:
We can’t use a /31 or /32 because we have to have at least 2 host bits for
assigning IP addresses to hosts.
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147. When you’ve chosen a possible subnet mask for your network and need to
determine the number of subnets, valid hosts, and broadcast addresses of
a subnet that the mask provides, all you need to do is answer five simple
questions:
• How many subnets does the chosen subnet mask produce?
• How many valid hosts per subnet are available?
• What are the valid subnets?
• What’s the broadcast address of each subnet?
• What are the valid hosts in each subnet?
How many subnets? 2s, I which s is the number of bits borrowed. For example,
in 11000000, the number of 1s gives us 22 subnets. In this example, there
are 4 subnets.
How many hosts per subnet? 2h -2, in which h is the number of host bits not
borrowed. For example, in 11000000, the number of 0s gives us 26 – 2
hosts. In this example, there are 62 hosts per subnet. You need to subtract 2 for
the subnet address and the broadcast address, which are not valid hosts.
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148. What are the valid subnets? 256 – subnet mask = block size, or increment
number. An example would be 256 – 192 = 64. The block size of a 192 mask is
always 64. Start counting at zero in blocks of 64 until you reach the subnet mask
value and these are your subnets. 0, 64, 128, 192.
What’s the broadcast address for each subnet? Since we counted our subnets in
the last section as 0, 64, 128, and 192, the broadcast address is always the
number right before the next subnet. For example, the 0 subnet has a broadcast
address of 63 because the next subnet is 64. The 64 subnet has a broadcast
address of 127 because the next subnet is 128. And so on.
What are the valid hosts? Valid hosts are the numbers between the subnets,
omitting the all 0s and all 1s. For example, if 64 is the subnet number and 127 is
the broadcast address, then 65–126 is the valid host range —it’s always the
numbers between the subnet address and the broadcast address.
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149. 192.168.10.33/28 Calculate all things???
255.255.255.11110000
192.168.10. 00100001
Number of network=16 {0,16,32,48,64,80,96,112,128,144,160
176,192,208,224,240}
Number of hosts=16-2=14
block size=16
Network ID ::192.168.10.32
first usable ::192.168.10.33
last usable ::192.168.10.46
broadcast address::192.168.10.47
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150. 192.168.10.65/26 (255.255.255.192) Calculate all things?
255.255.255.11000000
192.168.10. 01000001
number of network=4 {0,64,128,192}
number of hosts =64-2=62
Network ID ::192.168.10.64
first usable ::192.168.10.65
last usable ::192.168.10.126
broadcast address::192.168.10.127
Mohannad Al-Hanahnah
152. 172.16.0.0 = Network address
255.255.240.0 = Subnet mask
Calculate all things??
Number Subnets? 24 = 16
Number Hosts? 212 – 2 = 4094
Valid subnets? 256 – 240= 16 {0, 16, 32, 48, etc., up to 240}
Mohannad Al-Hanahnah
153. Given the Class C network of 204.15.5.0/24, subnet the network in order to create
the network in Figure with the host requirements shown.?
You need three subnet bits>>> 23 =8 subnetwork
Number of host >>>> 25 -2=32-2=30 hosts
Subnetmask >>>>255.255.255.224
Block size = 256- 25 =256-224=32
netA: 204.15.5.0/27 host address range 1 to 30
netB: 204.15.5.32/27 host address range 33 to 62
netC: 204.15.5.64/27 host address range 65 to 94
netD: 204.15.5.96/27 host address range 97 to 126
netE: 204.15.5.128/27 host address range 129 to 158
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154. In this example, you are given two address / mask combinations, written with the
prefix/length notation, which have been assigned to two devices. Your task is to
determine if these devices are on the same subnet or different subnets.??
DeviceA: 172.16.17.30/20
DeviceB: 172.16.28.15/20
DeviceA and DeviceB have addresses that are part of the same subnet.
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155. In all of the previous examples of subnetting, notice that the same subnet mask
was applied for all the subnets.
This means that each subnet has the same number of available host
addresses. You can need this in some cases, but, in most cases, having the
same subnet mask for all subnets ends up wasting address space.
Subnet 172.16.1.0/24 is divided into smaller subnets.
– Subnet with one mask (/27).
– Then further subnet one of the unused /27 subnets into multiple /30 subnets
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156. Given the Class C network of 204.15.5.0/24, subnet the network in order to create
the network in Figure with the host requirements shown.?
netA: 204.15.5.0/27
netB: 204.15.5.32/27
netC: 204.15.5.64/27
netD: 204.15.5.96/27
netE: 204.15.5.128/27
NetA, NetC, and NetD have a lot of unused host
address space. It is possible that this was a
deliberate design accounting for future growth, but
in many cases this is just wasted address space
due to the fact that the same subnet mask is being
used for all the subnets.
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157. Solution using VLSM::
netA: must support 14 hosts
netB: must support 28 hosts
netC: must support 2 hosts
netD: must support 7 hosts
netE: must support 28 host
Determine what mask allows the required number
of hosts.
netA: requires a /28
netB: requires a /27
netC: requires a /30
netD: requires a /28
netE: requires a /27
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158. Question: What subnet and broadcast address is the IP address 172.16.66.10 /18
a member of?
Answer: The interesting octet is the third octet instead of the fourth octet.
Block size=256 – 192 = 64.
0, 64, 128. The subnet is 172.16.64.0. The broadcast must be 172.16.127.255
since 128.0 is the next subnet.
Question: A router receives a packet on an interface with a destination address of
172.16.46.191/26. What will the router do with this packet?
Answer: 172.16.46.191/26 is a 255.255.255.192 mask, which gives us a block
size of 64. Our subnets are then 0, 64, 128, 192. 191 is the broadcast address of
the 128 subnet, so a router, by default, will discard any broadcast packets.
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159. introduced to improve both address space utilization and routing scalability in the
Internet. It was needed because of the rapid growth of the Internet and growth of
the IP routing tables held in the Internet routers.
CIDR moves way from the traditional IP classes (Class A, Class B, Class C, and so
on). In CIDR , an IP network is represented by a prefix, which is an IP address and
some indication of the length of the mask.
This allows for the summarization of the domains to be done at the higher level. For
example, if an ISP owns network 172.16.0.0/16, then the ISP can offer
172.16.1.0/24, 172.16.2.0/24, and so on to customers. Yet, when advertising to
other providers, the ISP only needs to advertise 172.16.0.0/16.
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161. Classful Routing Overview
– Classful routing protocols do not include the subnet mask with the network
in the routing advertisement.
– Within the same network, consistency of the subnet masks is assumed, one
subnet mask for the entire network.
– Summary routes are exchanged between foreign networks.
– Examples of classful routing protocols include:
• RIPv1
• IGRP
• Note: Classful routing protocols are legacy routing protocols typically used to
address compatibility issues.
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162. Classless Routing Overview
– Classless routing protocols include the subnet mask with the network in the
advertisement.
– Classless routing protocols support VLSM; one network can have multiple masks.
– Summary routes must be manually controlled within the network.
– Examples of classless routing protocols include:
• RIPv2
• EIGRP
• OSPF
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164. Introduction to Routers
A router is a special type of computer. It has the same basic components as a
standard desktop PC. However, routers are designed to perform some very specific
functions. Just as computers need operating systems to run software applications,
routers need the Internetwork Operating System software (IOS) to run configuration
files. These configuration files contain the instructions and parameters that control the
flow of traffic in and out of the routers. The many parts of a router are shown below:
Mohannad Al-Hanahnah
165. RAM
Random Access Memory, also called dynamic RAM (DRAM)
RAM has the following characteristics and functions:
• Stores routing tables
• Holds ARP cache
• Performs packet buffering (shared RAM)
• Provides temporary memory for the configuration file of
the router while the router is powered on
• Loses content when router is powered down or restarted
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166. NVRAM
Non-Volatile RAM
NVRAM has the following characteristics and functions:
• Provides storage for the startup configuration file
• Retains content when router is powered down or
restarted
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167. Flash
Flash memory has the following characteristics and
functions:
• Holds the operating system image (IOS)
• Allows software to be updated without
removing and replacing chips on the processor
• Retains content when router is powered down
or restarted
• Can store multiple versions of IOS software
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168. ROM
Read-Only Memory
ROM has the following characteristics and functions:
• Maintains instructions for power-on self test
(POST) diagnostics
• Stores bootstrap program and basic operating
system software
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170. Interfaces
Interfaces have the following characteristics and functions:
• Connect router to network for frame entry and exit
• Can be on the motherboard or on a separate module
Types of interfaces:
• Ethernet
• Fast Ethernet
• Serial
• Token ring
• ISDN BRI
• Console
• Aux
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174. Fixed Interfaces
When cabling routers for serial connectivity, the routers will either have
fixed or modular ports. The type of port being used will affect the syntax
used later to configure each interface.
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176. Router Power-On/Bootup
Sequence
1. Perform power-on self test (POST).
2. Load and run bootstrap code.
3. Find the Cisco IOS software.
4. Load the Cisco IOS software.
5. Find the configuration.
6. Load the configuration.
7. Run the configured Cisco IOS software.
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178. show version Command
Router#show version
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-JS-M), Version 12.0(7a), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2002 by cisco Systems, Inc.
Compiled Tue 05-Feb-02 01:48 by pwade
Image text-base: 0x80008088, data-base: 0x80B0404C
ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)
Router uptime is 1 minute
System restarted by reload
System image file is "flash:c2600-js-mz.120-7a.bin"
cisco 2610 (MPC860) processor (revision 0x300) with 53248K/12288K bytes of memory.
Processor board ID JAD06090BMD (2719249260)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
SuperLAT software (copyright 1990 by Meridian Technology Corp).
TN3270 Emulation software.
Basic Rate ISDN software, Version 1.1.
1 Ethernet/IEEE 802.3 interface(s)
2 Serial(sync/async) network interface(s)
1 ISDN Basic Rate interface(s)
32K bytes of non-volatile configuration memory.
16384K bytes of processor board System flash (Read/Write)
Configuration register is 0x2102
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190. Configuring an Interface
Router(config)#interface type number
Router(config-if)#
• type includes serial, ethernet, token ring, fddi, hssi, loopback,
dialer, null, async, atm, bri, tunnel, and so on
• number is used to identify individual interfaces
Router(config)#interface type slot/port
Router(config-if)#
• For modular routers, selects an interface
Router(config-if)#exit
• Quits from current interface configuration mode
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191. Configuring an Interface
Description
RouterX(config-if)# description string
string is a comment or a description to help you remember
what is attached to this interface.
The maximum number of characters for the string argument
is 238.
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192. Disabling or Enabling an Interface
RouterX#configure terminal
RouterX(config)#interface serial 0
RouterX(config-if)#shutdown
%LINK-5-CHANGED: Interface Serial0, changed state to administratively down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down
Administratively turns off an interface
RouterX#configure terminal
RouterX(config)#interface serial 0
RouterX(config-if)#no shutdown
%LINK-3-UPDOWN: Interface Serial0, changed state to up
%LINEPROTO-5-UPDOWN: Line Protocol on Interface Serial0, changed state to up
Enables an interface that is administratively shut down
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193. Serial Interface show controller
Command
Router#show controller serial 0
HD unit 0, idb = 0x121C04, driver structure at 0x127078
buffer size 1524 HD unit 0, V.35 DTE Cable
cable
.
.
.
• Shows the cable type of serial cables
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194. Setting
the Clock
with Help
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195. Configuring Interfaces
An interface needs an IP Address and a Subnet Mask to be configured.
All interfaces are “shutdown” by default.
The DCE end of a serial interface needs a clock rate.
Router#config t
Router(config)#interface serial 0/1
Router(config-if)#ip address 200.100.50.75 255.255.255.240
Router(config-if)#clock rate 56000 (required for serial DCE only)
Router(config-if)#no shutdown
Router(config-if)#exit
Router(config)#int f0/0
Router(config-if)#ip address 150.100.50.25 255.255.255.0
Router(config-if)#no shutdown
Router(config-if)#exit
Router(config)#exit
Router#
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197. Examining the show Commands
There are many show commands that can be used to examine the contents of files
in the router and for troubleshooting. In both privileged EXEC and user EXEC
modes, the command show ? provides a list of available show commands. The list
is considerably longer in privileged EXEC mode than it is in user EXEC mode.
show interfaces – Displays all the statistics for all the interfaces on the router.
show int s0/1 – Displays statistics for interface Serial 0/1
show controllers serial – Displays information-specific to the interface hardware
show clock – Shows the time set in the router
show hosts – Displays a cached list of host names and addresses
show users – Displays all users who are connected to the router
show history – Displays a history of commands that have been entered
show flash – Displays info about flash memory and what IOS files are stored there
show version – Displays info about the router and the IOS that is running in RAM
show ARP – Displays the ARP table of the router
show start – Displays the saved configuration located in NVRAM
show run – Displays the configuration currently running in RAM
show protocol – Displays the global and interface specific status of any configured
Layer 3 protocols
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198. Cisco Discovery Protocol “CDP”
– Cisco Discovery Protocol is a proprietary utility that provides
a summary of directly connected switches, routers, and
other Cisco devices.
– Cisco Discovery Protocol discovers neighboring devices,
regardless of which protocol suite they are running.
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199. Discovering Neighbors with Cisco
Discovery Protocol
– Cisco Discovery Protocol runs on
Cisco IOS devices.
– Summary information includes:
– Device identifiers
– Address list
– Port identifier
– Capabilities list
– Platform
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200. Using Cisco Discovery Protocol
RouterA#show cdp ?
entry Information for specific neighbor entry
interface CDP interface status and configuration
neighbors CDP neighbor entries
traffic CDP statistics
…
RouterA(config)#no cdp run
! Disable CDP Globally
RouterA(config)#interface serial0/0/0
RouterA(config-if)#no cdp enable
! Disable CDP on just this interface
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201. Using the show cdp neighbors
Command
RouterA#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater
Device ID Local Intrfce Holdtme Capability Platform Port ID
SwitchA fa0/0 122 S I WS-C2960 fa0/2
RouterB s0/0/0 177 R S I 2811 s0/0/1
Mohannad Al-Hanahnah
202. Using the show cdp entry
Command
Device ID: RouterB
Entry address(es):
IP address: 10.1.1.2
Platform: Cisco 2811, Capabilities: Router Switch IGMP
Interface: Serial0/0/0, Port ID (outgoing port): Serial0/0/1
Holdtime : 155 sec
Version :
Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M),
Version 12.4(12), RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Fri 17-Nov-06 12:02 Mohannad Al-Hanahnah
by prod_rel_team
203. Additional Cisco Discovery Protocol
Commands
RouterA#show cdp traffic
CDP counters :
Total packets output: 8680, Input: 8678
Hdr syntax: 0, Chksum error: 0, Encaps failed: 5
No memory: 0, Invalid packet: 0, Fragmented: 0
CDP version 1 advertisements output: 0, Input: 0
CDP version 2 advertisements output: 8680, Input: 8678
RouterA#show cdp interface s0/0/0
Serial0/0/0 is up, line protocol is up
Encapsulation PPP
Sending CDP packets every 60 seconds
Holdtime is 180 seconds Mohannad Al-Hanahnah
205. Anatomy of an IP Packet
IP packets consist of the data from upper layers plus an IP
header. The IP header consists of the following:
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206. Static vs. Dynamic Routes
Routing is the process that a router uses to forward packets toward
the destination network. A router makes decisions based upon the
destination IP address of a packet. All devices along the way use the
destination IP address to point the packet in the correct direction so
that the packet eventually arrives at its destination. In order to make
the correct decisions, routers must learn the direction to remote
networks.
• Static Route • Dynamic Route
–Uses a route that a
– Uses a route
network routing
that a network
protocol adjusts
administrator
automatically for
enters into the
topology or traffic
router manually
changes
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207. Static Routes
• Configure unidirectional static routes to and from a
stub network to allow communications to occur.
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210. Default Routes
• This route allows the stub network to reach all known
networks beyond router A.
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211. Verifying the Static
Route Configuration
router#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
U - per-user static route
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
10.0.0.0/8 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, Serial0
S* 0.0.0.0/0 is directly connected, Serial0
Mohannad Al-Hanahnah
212. What Is a Dynamic Routing
Protocol?
Routing protocols are
used between routers to
determine paths to remote
networks and maintain
those networks in the
routing tables.
After the path is determined,
a router can route a routed
protocol to the learned networks.
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213. Autonomous Systems: Interior and
Exterior Routing Protocols
An autonomous system is a collection of networks within
a common administrative domain.
Interior gateway protocols operate within an autonomous system.
Exterior gateway protocols connect different autonomous systems.
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216. Classful Routing Protocol
– Classful routing protocols do not include the
subnet mask with the route advertisement.
– Within the same network, consistency of the
subnet masks is assumed.
– Summary routes are exchanged between foreign
networks.
– These are examples of classful routing protocols:
• RIPv1
• IGRP
Mohannad Al-Hanahnah
217. Classless Routing Protocol
– Classless routing protocols include the subnet mask with
the route advertisement.
– Classless routing protocols support a variable-length
subnet mask (VLSM).
– Summary routes can be manually controlled within the
network.
– These are examples of classless routing protocols:
• RIPv2
• EIGRP
• OSPF
• IS-IS
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222. Inconsistent Routing Entries:
Counting to Infinity and Routing Loops
Each node maintains the distance from itself
to each possible destination network.
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224. Counting to Infinity (Cont.)
Router C concludes that the best path to
network 10.4.0.0 is through router B.
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225. Counting to Infinity (Cont.)
Router A updates its table to reflect
the new but erroneous hop count.
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226. Counting to Infinity (Cont.)
The hop count for network 10.4.0.0 counts to infinity.
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227. Solution to Counting to Infinity:
Defining a Maximum
A limit is set on the number of hops to prevent infinite loops.
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228. Routing Loops
Packets for network 10.4.0.0 bounce
(loop) between routers B and C.
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229. Solution to Routing Loops: Split
Horizon
It is never useful to send information about a route back
in the direction from which the original information came.
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230. Solution to Routing Loops:
Route Poisoning and Poison Reverse
Routers advertise the distance of routes
that have gone down to infinity.
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231. Solution to Routing Loops:
Route Poisoning and Poison Reverse (Cont.)
Poison reverse overrides split horizon.
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232. Solution to Routing Loops:
Hold-Down Timers
The router keeps an entry for the “possibly down” state in the network,
allowing time for other routers to recompute for this topology change.
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234. Link-State Routing Protocols
After an initial flood of LSAs, link-state routers pass small,
event-triggered link-state updates to all other routers.
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235. OSPF Hierarchical Routing
Consists of areas and autonomous systems
Minimizes routing update traffic
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237. Benefits and Drawbacks of Link-State Routing
– Benefits of link-state routing:
• Fast convergence:
– Changes are reported immediately by the affected source
• Robustness against routing loops:
– Routers know the topology
– Link-state packets are sequenced and acknowledged
• Hierarchical network design enables optimization of resources.
– Drawbacks of link-state routing:
• Significant demands for resources:
– Memory (three tables: adjacency, topology, forwarding)
– CPU
• Requires very strict network design
• Configuration can be complex when tuning various parameters and
when design is complex
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238. RIP Overview
– Hop-count metric selects the path
– Routes update every 30 seconds
– Administrative distance 120
239. RIPv1 and RIPv2 Comparison
RIPv1 RIPv2
Routing protocol Classful Classless
Supports variable-length subnet mask? No Yes
Sends the subnet mask along with the routing
No Yes
update?
Addressing type Broadcast Multicast
RFCs 1721, 1722,
Defined in … RFC 1058
and 2453
Supports manual route summarization? No Yes
Authentication support? No Yes
240. RIP Configuration
RouterX(config)# router rip
–Starts the RIP routing process
RouterX(config-router)# version 2
Enables RIP version 2
RouterX(config-router)# network network-number
Selects participating attached networks
Requires a major classful network number
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242. Verifying the RIP Configuration
A#show ip protocol
Routing Protocol is "rip"
Sending updates every 30 seconds, next due in 6 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Redistributing: rip
Default version control: send version 2, receive version 2
Interface Send Recv Triggered RIP Key-chain
FastEthernet0/0 2 2
Serial0/0/2 2 2
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
10.0.0.0
172.16.0.0
Routing Information Sources:
Gateway Distance Last Update
10.1.1.2 120 00:00:25
Distance: (default is 120)Mohannad Al-Hanahnah
243. Displaying the IP Routing Table
RouterA# show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default
U - per-user static route, o - ODR
T - traffic engineered route
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 1 subnets
C 172.16.1.0 is directly connected, fastethernet0/0
10.0.0.0/24 is subnetted, 2 subnets
R 10.2.2.0 [120/1] via 10.1.1.2, 00:00:07, Serial0/0/2
C 10.1.1.0 is directly connected, Serial0/0/2
R 192.168.1.0/24 [120/2] via 10.1.1.2, 00:00:07, Serial0/0/2
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244. debug ip rip Command
RouterA# debug ip rip
RIP protocol debugging is on
RouterA#
00:06:24: RIP: received v1 update from 10.1.1.2 on Serial0/0/2
00:06:24: 10.2.2.0 in 1 hops
00:06:24: 192.168.1.0 in 2 hops
00:06:33: RIP: sending v1 update to 255.255.255.255 via FastEthernet0/0 (172.16.1.1)
00:06:34: network 10.0.0.0, metric 1
00:06:34: network 192.168.1.0, metric 3
00:06:34: RIP: sending v1 update to 255.255.255.255 via Serial0/0/2 (10.1.1.1)
00:06:34: network 172.16.0.0, metric 1
Mohannad Al-Hanahnah
245. EIGRP Features
Advanced distance vector Flexible network design
Rapid convergence Multicast and unicast instead of broadcast
Easy configuration address
Incremental updates Support for VLSM and discontiguous subnets
Support for multiple network layer protocols
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250. Verifying the EIGRP Configuration
RouterX# show ip route eigrp
Displays the current EIGRP entries in the routing table
RouterX# show ip protocols
Displays the parameters and current state of the active process
RouterX# show ip eigrp interfaces
Displays information about interfaces configured for EIGRP
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251. Verifying the EIGRP Configuration
(Cont.)
RouterX# show ip eigrp neighbors
Displays the neighbors discovered by IP EIGRP
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252. Verifying the EIGRP Configuration
(Cont.)
RouterX# show ip eigrp topology
Displays the IP EIGRP topology table
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253. Verifying the EIGRP Configuration
(Cont.)
RouterX# show ip eigrp traffic
Displays the number of IP EIGRP packets sent and received
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254. debug ip eigrp Command
RouterX# debug ip eigrp
IP-EIGRP: Processing incoming UPDATE packet
IP-EIGRP: Ext 192.168.3.0 255.255.255.0 M 386560 - 256000 130560 SM 360960 –
256000 104960
IP-EIGRP: Ext 192.168.0.0 255.255.255.0 M 386560 - 256000 130560 SM 360960 –
256000 104960
IP-EIGRP: Ext 192.168.3.0 255.255.255.0 M 386560 - 256000 130560 SM 360960 –
256000 104960
IP-EIGRP: 172.69.43.0 255.255.255.0, - do advertise out Ethernet0/1
IP-EIGRP: Ext 172.69.43.0 255.255.255.0 metric 371200 - 256000 115200
IP-EIGRP: 192.135.246.0 255.255.255.0, - do advertise out Ethernet0/1
IP-EIGRP: Ext 192.135.246.0 255.255.255.0 metric 46310656 - 45714176 596480
IP-EIGRP: 172.69.40.0 255.255.255.0, - do advertise out Ethernet0/1
IP-EIGRP: Ext 172.69.40.0 255.255.255.0 metric 2272256 - 1657856 614400
IP-EIGRP: 192.135.245.0 255.255.255.0, - do advertise out Ethernet0/1
IP-EIGRP: Ext 192.135.245.0 255.255.255.0 metric 40622080 - 40000000 622080
IP-EIGRP: 192.135.244.0 255.255.255.0, - do advertise out Ethernet0/1
Note: EIGRP routes are exchanged only when a change in topology occurs.
Mohannad Al-Hanahnah
255. EIGRP Metric
• The criteria that EIGRP uses by default to calculate its
metric:
– Bandwidth
– Delay
• The optional criteria that EIGRP can be configured to use
when calculating its metric:
– Reliability
– Load
• Note: Although MTU is exchanged in EIGRP packets between
neighbor routers, MTU is not factored into the EIGRP metric
calculation.
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256. EIGRP Load Balancing
– By default, EIGRP does equal-metric load
balancing:
• By default, up to four routes with a metric equal to
the minimum metric are installed in the routing
table.
– There can be up to 16 entries in the routing
table for the same destination:
• The number of entries is configurable with the
maximum-paths command.
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257. OSPF Overview
– (OSPF) is an open standard routing protocol
– Creates a neighbor relationship by exchanging hello packets
– Floods LSAs to all OSPF routers in the area, not just directly connected
routers
– Pieces together all the LSAs generated by the OSPF routers to create
the OSPF link-state database
– Uses the SPF algorithm to calculate the shortest path to each
destination and places it in the routing table
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258. OSPF Hierarchy Example
Minimizes routing table entries
Localizes the impact of a topology change within an area
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260. SPF Algorithm
10
10
1
1
1
Places each router at the root of a tree and calculates the
shortest path to each destination based on the cumulative cost
Cost = Reference Bandwidth / Interface Bandwidth (b/s)
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261. Configuring Wildcards
If you want to advertise a partial octet (subnet),
you need to use wildcards.
– 0.0.0.0 means all octets match exactly
– 0.0.0.255 means that the first three match exactly,
but the last octet can be any value
After that, you must remember your block sizes….
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262. Wildcard
The wildcard address is always one less than the block
size….
– 192.168.10.8/30 = 0.0.0.3
– 192.168.10.48/28 = 0.0.0.15
– 192.168.10.96/27 = 0.0.0.31
– 192.168.10.128/26 = 0.0.0.63
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263. Configuring Single-Area OSPF
RouterX(config)#
router ospf process-id
Defines OSPF as the IP routing protocol
RouterX(config-router)#
network address wildcard-mask area area-id
Assigns networks to a specific OSPF area
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264. Verifying the OSPF Configuration
Router#show ip protocols
• Verifies that OSPF is configured
Router#show ip route
• Displays all the routes learned by the router
Router#show ip ospf interface
• Displays area-ID and adjacency information
Router#show ip ospf neighbor
• Displays OSPF-neighbor information on a per-interface basis
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270. Transmitting Frames
Cut-Through Store and Forward
• Switch checks destination address Complete frame is received and
and immediately begins checked before forwarding.
forwarding frame.
Fragment-Free
• Switch checks the first 64 bytes,
then immediately
begins forwarding frame.
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271. Layer 2 Addressing
– MAC address
– Assigned to end devices
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272. MAC Address Table
• Initial MAC address table is empty.
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273. Learning Addresses
• Station A sends a frame to station C.
• Switch caches the MAC address of station A to port E0 by
learning the source address of data frames.
• The frame from station A to station C is flooded out to all
ports except port E0 (unknown unicasts are flooded).
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274. Learning Addresses (Cont.)
• Station D sends a frame to station C.
• Switch caches the MAC address of station D to port E3 by
learning the source address of data frames.
• The frame from station D to station C is flooded out to all ports
except port E3 (unknown unicasts are flooded).
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275. Filtering Frames
• Station A sends a frame to station C.
• Destination is known; frame is not flooded.
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276. Filtering Frames (Cont.)
• Station A sends a frame to station B.
• The switch has the address for station B in the MAC
address table.
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306. Redundant Topology
Redundant topology eliminates single points of failure.
Redundant topology causes broadcast storms, multiple
frame copies, and MAC address table instability problems.
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307. Broadcast Frames
Station D sends a broadcast frame.
Broadcast frames are flooded to all ports
except the originating port.
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308. Broadcast Storms
Host X sends a broadcast.
Switches continue to propagate
broadcast traffic over and over.
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309. Multiple Frame Copies
Host X sends a unicast frame to router Y.
The MAC address of router Y has not been
learned by either switch.
Router Y will receive two copies of the same frame.
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310. MAC Database Instability
Host X sends a unicast frame to router Y.
The MAC address of router Y has not been learned by either switch.
Switches A and B learn the MAC address of host X on port 1.
The frame to router Y is flooded.
Switches A and B incorrectly learn the MAC address of host X on port 2.
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311. Loop Resolution with STP
Provides a loop-free redundant network topology
by placing certain ports in the blocking state
Published in the IEEE 802.1D specification
Enhanced with the Cisco PVST+ implementation
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312. Spanning-Tree Operation
One root bridge per broadcast domain.
One root port per nonroot bridge.
One designated port per segment.
Nondesignated ports are unused.
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313. STP Root Bridge Selection
BPDU (default = sent every 2 seconds)
Root bridge = bridge with the lowest bridge ID
Bridge ID = Bridge MAC
Priority Address
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317. Configuring and Verifying PortFast
SwitchX(config-if)#
spanning-tree portfast
Configures PortFast on an interface
OR
SwitchX(config)#
spanning-tree portfast default
Enables PortFast on all non-trunking interfaces
SwitchX#
show running-config interface interface
Verifies that PortFast has been configured on an interface
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324. Default Spanning-Tree
Configuration
– Cisco Catalyst switches support three types of
STPs:
• PVST+
• PVRST+
• MSTP
– The default STP for Cisco Catalyst switches is
PVST+ :
• A separate STP instance for each VLAN
• One root bridge for all VLANs
• No load sharing
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325. PVRST+ Configuration Guidelines
1. Enable PVRST+.
2. Designate and configure a switch to be the root bridge.
3. Designate and configure a switch to be the secondary
root bridge.
4. Verify the configuration.
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329. Configuring the Root and
Secondary Bridges: SwitchA
SwitchA(config)#
spanning-tree vlan 1 root primary
This command forces this switch to be the root for VLAN 1.
SwitchA(config)#
spanning-tree vlan 2 root secondary
This command configures this switch to be the secondary root
for VLAN 2.
OR
SwitchA(config)#
spanning-tree vlan # priority priority
This command statically configures the priority (increments of 4096).
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330. Configuring the Root and
Secondary Bridges: SwitchB
SwitchB(config)#
spanning-tree vlan 2 root primary
This command forces the switch to be the root for VLAN 2.
SwitchB(config)#
spanning-tree vlan 1 root secondary
This command configures the switch to be the secondary root VLAN 1.
OR
SwitchB(config)#
spanning-tree vlan # priority priority
This command statically configures the priority (increments of 4096).
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333. Virtual LANs (VLANs)
• Definition: A logical grouping of network users and
resources connected to administratively defined
ports on a switch.
– Smaller broadcast domains
– Organized by:
• Location
• Function
• Department
• Application or protocol
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335. Features of VLANs
• Simplify network management
• Provides a level of security over a
flat network
• Flexibility and Scalability
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337. Flexibility & Scalability
• Layer-2 switches only read frames
– Can cause a switch to forward all broadcasts
• VLANs
– Essentially create broadcast domains
• Greatly reduces broadcast traffic
• Ability to add wanted users to a VLAN regardless of their
physical location
• Additional VLANs can be created when network growth
consumes more bandwidth
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341. VLAN Memberships
• Static VLANs
– Typical method of creating VLANs
– Most secure
• A switch port assigned to a VLAN always maintains that assignment
until changed
• Dynamic VLANs
– Node assignment to a VLAN is automatic
• MAC addresses, protocols, network addresses, etc
– VLAN Management Policy Server (VMPS)
• MAC address database for dynamic assignments
• MAC-address to VLAN mapping
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