1
Networks Fundamentals
Based On Cisco Systems
2
Course Introduction
3
Cisco Career Certifications
CCNA Exam 640-801
CCIE
CCNP
Expert
Professional
Required
Exam
Recommended Training Through
Cisco Learning Partners
CCNA
Cisco Certified Network Associate
INTRO and
ICND
CCNA
Associate
Introduction to Cisco Networking
Technologies and Interconnecting
Cisco Network Devices
http://www.cisco.com/go/certifications4
Course Topics
- Day 1 : Introduction , OSI & TCP/IP Introduction
- Day 2 : OSI & TCP/IP Layers
- Day 3 : IP Addressing
- Day 4 : Introduction to Cisco IOS
- Day 5 : Routing Fundamentals & WAN Overview
5
Networking Technologies
• Network:
is basically all the components (H/W &
S/W) involved in connecting computer across
small and large distance
• Importance of Networks:
Easy access and sharing of information
Sharing of expensive devices and network
resources
Modern Technologies (IP telephony, Video
on Demand, ….etc)
6
Network components
• Network has three main components
 Computers (servers and hosts)
- Source of applications (network aware applications)
- ex: HTTP (Hyper Text Transmission Protocol),
FTP (File Transfer Protocol),
SNMP (Simple Network Management Protocol)
Telnet
 Network Devices
- Devices that interconnect different computers together
- ex: Repeaters, hub, bridge, switch, router, NIC and modems
 Connectivity
- Media that physically connect the computers and network devices
- ex: Wireless and cables
7
Network Types
• LAN (Local Area Network):
It is a group of network components that work
within small area
• MAN (Metropolitan Area Network):
It is a group of LANs that are interconnected
within small area
• WAN (Wide Area Network):
It is a group of LANs that are interconnected
within large area
8
Reference Models
- describe data transfer standards
- a framework (guideline) for network
implementation and troubleshooting
- divides complex functions in to simpler
components
- Reference model types :
- OSI
- TCP/IP
9
Reference Models
7 Application
6 Presentation
Application
5 Session
4 Transport
Transport
3 Network
Internet
2 Data Link
Network
Access
1 Physical
10
OSI Model Overview
Application
Application
(Upper)
Layers
Presentation
Session
Transport Layer
Network Layer
Data Link
Data Flow
Layers
Physical
11
The OSI Reference model
transmission example
A
B
7 Application
7 Application
6 Presentation
6 Presentation
5 Session
5 Session
4 Transport
4 Transport
3 Network
3 Network
2 Data Link
2 Data Link
1 Physical
1 Physical
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Encapsulation Process
13
Layer 7 - The Application Layer
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical
This layer deals with
networking applications.
Examples:

Email

Web browsers
Each application uses a
certain service from
Transport Layer
(reliable or unreliable)
PDU - User Data
14
Layer 6 - The Presentation Layer
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical
- Presenting the data in
the required format which
may include:
 Encryption
 Compression
- Translates between
multiple data format by
using a common format .
PDU - Formatted Data
15
Layer 5 - The Session Layer
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
Establishes, manages, and
terminates sessions between two
communicating hosts.
Example:

Client Software
( Used for logging in)
PDU - Formatted Data
1 Physical
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Layer 4 - The Transport Layer
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
-Breaks up the data from the
sending host and then
reassembles it in the receiver.
(segmentation)
-Insure reliable data transport
across the network
(reliability and flow control)
PDU - Segments
1 Physical
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Layer 3 - The Network Layer
7 Application
-Logical addressing (IP address)
6 Presentation
- Selects the best Path Determination
(routing)
5 Session
4 Transport
PDU - Packets
3 Network
2 Data Link
1 Physical
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Layer 2 - The Data Link Layer
7 Application
6 Presentation
- provides reliable transit of data
across a physical link hop by hop
4 Transport
- Makes decisions based on
physical addresses
(usually MAC addresses)
3 Network
- Provides error detection
5 Session
2 Data Link
PDU - Frames
1 Physical
19
Layer 1 - The Physical Layer
7 Application
6 Presentation
5 Session
4 Transport
This is the physical media
through which the data,
represented as electronic
signals, is sent from the source
host to the destination host.
2 Data Link
Examples:

UTP

Coaxial (like cable TV)

Fiber optic
1 Physical
PDU - Bits
3 Network
20
TCP/IP model
7 Application
6 Presentation
Application
5 Session
4 Transport
Transport
3 Network
Internet
2 Data Link
Network
Access
1 Physical
21
Hierarchical Network Model
22
The Physical Layer
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23
Physical Layer Responsibilities
Description of LAN/WAN cables & connectors
Description of LAN/WAN standards
(maximum length, bit rates, pin assignment, voltage levels)
Physical Layer Devices
24
LAN Physical Layer
Ethernet cables :
- Copper ( UTP , STP , Coaxial )
- Fiber
25
Unshielded Twisted Pair (UTP) Cable
prevents EMI , RFI
CAT5
CAT 5e , CAT6
RJ-45
to avoid attenuation
26
Using UTP cable to connect devices
1- straight cable
2- cross cable
3- roll over cable
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Straight-Through or Crossover cables
Cross
cable
switch
PC
hub
router
Cross
cable
modem
straight
cable
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Shielded Twisted Pair (STP) Cable
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Coaxial Cable
thick coaxial , thin coaxial (200 m)
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Fiber Optic Cable
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Fiber Optic Connectors
single mode fiber
multimode fiber
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WAN Physical Layer
serial cables
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Transmission modes
- Full duplex :
devices can send , receive data at the
same time (two ways for transmission)
- Half duplex:
one circuit for transmission , so only one
device can use the bus (send or receive)
at a time , if two devices sent at the same
time collision occurs .
34
Layer 1 devices
1- 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. Rule : no more than four
repeaters can be used between hosts on a LAN.
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2- Hub
A Hub is a multi-port
Repeater
Hubs takes data bits from
input port and forward it to
all other ports
repeater and hub work in
half duplex mode
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The Data-Link Layer
37
37
Data-Link Layer Responsibilities
Description of H/W addressing
MAC (Media Access Control) address
frame format
Error detection between hop to hop
Data-Link layer standards :
LAN: Ethernet, Token Ring, FDDI
WANs: HDLC, PPP, ISDN, X.25, Frame-Relay, ATM
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Ethernet Overview
- Ethernet is now the dominant LAN technology in the world.
- Ethernet is not one technology but a family of LAN
technologies.
- Ethernet specifications support different media,
bandwidths, and other Layer 1 and 2 variations.
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MAC Address
- MAC address is 48 bits in length and expressed as twelve
hexadecimal digits.
- MAC addresses are burned into read-only memory (ROM) of the NIC
- each NIC has a unique MAC address
- MAC address can represent unicast , broadcast and multicast
ex.
A34C.52BD.1234
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Ethernet Frame Structure
41
Layer 2 devices
• A layer 2 device is a device that understand MAC,
for example:
 NIC (Network Interface Card)
 Bridge :
- address learning
- forwarding decisions are based on software
- bridge is used for LAN segmentation
 Switch:
- a multi-port bridge
- forwarding decisions are based on hardware ASIC
(faster than bridge)
42
Ethernet Switches and Bridges
• Transparent Bridge and Switches has 3 main
functions
 Address learning
 Forward/filter decision
 Loop avoidance
43
1- Address Learning
Switch learns which MAC’s are connected to
which ports by checking the frame source
MAC address .
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2- Forwarding
- Forwarding is done by checking the destination MAC address
- The frame is flooded if the destination MAC is unknown unicast or
broadcast or multicast
- for the known unicast, switch perform micro segmentation45
Forwarding modes
Cut-Through
• Switch checks destination
address and immediately
begins forwarding frame.
Store and Forward
Complete frame is received
and checked before
forwarding.
Fragment-Free
• Switch checks
the first 64 bytes, then
begins forwarding frame.
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3- Remove Layer 2 loops
MAC
port
A
3
A
1
• Solution : using Spanning tree protocol (STP)
47
Frame creation
Source
MAC
Burned
on the NIC
Destination
MAC
Source
IP
- ARP
- Static
- Proxy ARP
- Dynamic
(RARP ,
BOOTP ,
DHCP)
Destination
IP
DNS
48
- Source MAC
Burned
on the NIC
49
- Source IP
1- by static configuration
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- Source IP
- DHCP :
- Dynamic host configuration
protocol
- DHCP allows a host to obtain
an IP address dynamically
without the network
administrator having to set
up an individual profile for
each device.
- a range of IP addresses on a
DHCP server is defined .
- the entire network
configuration of a computer
can be obtained in one
message from the server.
51
- Destination IP
DNS :
• Application specified in the TCP/IP suite
• Means to translate human-readable names into IP
addresses
52
- Destination MAC
- ARP :
- each PC
form an
ARP table
containing
the learned
MAC’s
53
- Destination MAC
- Proxy ARP :
A
B
A
B
Router R
I take care, to forward
IP packets to B
Broadcast Message to all:
If your IP address matches “B”
then please tell me your
Ethernet address
Yes, I know the destination
network, let me give you my
Ethernet address
54
The Transport Layer
55
55
The Transport Layer
reliable
service
unreliable
service
56
Flow Control
- Windowing (PAR):
error in
2
2
2
2
3
3
Flow Control
- Windowing (PAR):
58
Multiplexing applications
2
1
12.0.0.1
13.0.0.1
web server
12.0.0.2
3
Source IP
Destination IP Source port Destination port
1
12.0.0.1
13.0.0.1
1200
80
2
12.0.0.1
13.0.0.1
1500
80
3
12.0.0.2
13.0.0.1
1200
80
59
TCP Header
UDP Header
The Application Layer
62
62
TCP/IP Application Layer Overview
• File transfer
– FTP
– TFTP
• E-mail
– Simple Mail Transfer Protocol
• Remote login
– Telnet
• Network management
– Simple Network Management
Protocol
• Name management
– Domain Name System
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Port Numbers
64
The TCP/IP Internet Layer
65
65
Internet Layer
• Internet Layer is responsible for the following:
 Support of logical addressing for network components
 Routing (Finding the best path for data)
 Layer 3 devices
• Internet Layer protocols are
 IP (Internet Protocol)
 ICMP (Internet Control Management Protocol)
 ARP (Address Resolution Protocol), RARP (Revere ARP)
 Routing Protocols ex. OSPF , EIGRP ,
66
IP (Internet Protocol)
• IP has the following characteristics
 Provide Logical addressing
 Provide connectionless “best effort” delivery of data
67
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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IP addressing
- Each host in the network must have a unique IP address
because duplicate addresses would make routing impossible
- IP Addressing is a hierarchical structure as the IP address
combines two identifiers into one number .
the first part identifies the network address , the second part,
called the host part, identifies which particular machine
it is on the network.
- IP address is a 32 bit (4 bytes= 4 octets) address that is
mainly divided to network part (representing the network ID
where the device is located in) & Host part (representing the
ID of the host)
- It is represented in a dotted decimal form, where each octet
is transformed to its decimal value.
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ex. 192.168.1.3
IP Address Classes
IP addresses are divided into classes to define the large,
medium, and small networks.
Class A addresses are assigned to larger networks.
Class B addresses are used for medium-sized networks,
Class C for small networks,
Class D for Multicasting
Class E for Experimental purposes
70
Identifying Address Classes
Note : for Class A , networks 0 & 127 are reserved (class A range 1 - 126)
71
Public IP Addresses
- Unique addresses are required for each device on a network
- Originally, an organization known as the Internet Assigned
Numbers Authority (IANA) handled this procedure.
- No two machines that connect to a public network can have
the same IP address because public IP addresses are global
and standardized.
72
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.
73
IP address types
• IP address could be one of three categories
 Network address
 Host address
 Broadcast address
74
Network / Broadcast Addresses
- Network address :
the first IP address in it which all host part bits = 0
- Broadcast address:
the last IP address in the network which all host part bits = 1
no. of host bits
- other addresses are host addresses = 2
- Here are some examples:
-2
Class
Network Address
Broadcast Address
A
12.0.0.0
12.255.255.255
B
172.16.0.0
172.16.255.255
C
192.168.1.0
192.168.1.255
75
Subnet Mask
- 32 bit mask ( 1’s followed by 0’s )
- Used by routers and hosts to determine the number of
network- significant bits ( identified by 1’s )
and host- significant bits in an IP address (identified by 0’s)
- example :
Class
A
B
C
Network Address
12.0.0.0
172.16.0.0
192.168.0.0
Default subnet mask
255.0.0.0
or
255.255.0.0
or
255.255.255.0
or
/8
/16
/24
76
Octet Values of a Subnet Mask
• Subnet masks like IP addresses can be represented in the dotted
decimal format like 255.255.255.0.
77
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.
- Subnetting is done by taking part of host bits then add it to
the network part
IP
address
Network part
Host part
Subnet
bits
Network part
Host part
78
Subnetting Example
Divide network 192.168.1.0/24 into 4 subnets
Solution: 4 subnets need 2 bits
192.168.1 . 0
192.168.1 . 0000 0000 to 0011 1111
192.168.1 . 0100 0000 to 0111 1111
192.168.1 . 1000 0000 to 1011 1111
192.168.1 . 1100 0000 to 1111 1111
subnet mask is 255.255.255.192 or /26
The first subnet is
192.168.1.0/26
The second subnet is 192.168.1.64/26
The third subnet is
192.168.1.128/26
The fourth subnet is
192.168.1.192/26
0 - 63
64 - 127
128 - 191
192 - 255
79
Divide network 192.168.1.0/24 into 4 subnets
Solution :
- 4 subnets need 2 bits
- subnet mask = 255.255.255.192
- interesting octet is 192
- hop count = 256 – 192 = 64
- The first subnet is
192.168.1.0/26
- The second subnet is 192.168.1.64/26
- The third subnet is
192.168.1.128/26
- The fourth subnet is
192.168.1.192/26
80
Determine if this IP is network address or host
address or broadcast address
172.16.5.0/23
Solution :
- subnet mask = 255.255.254.0
- interesting octet is 254
- hop count = 256 – 254 = 2
- The first subnet is
172.16.0.0/23
- The second subnet is 172.16.2.0/23
- The third subnet is
172.16.4.0/23
- The fourth subnet is
172.16.6.0/23
So 172.16.5.0/23 is a host address
172.16.5.0/23
81
- Which IP address should be assigned to PC B ?
A . 192.168.5.5
B . 192.168.5.32
C . 192.168.5.40
D . 192.168.5.63
E . 192.168.5.75
A
B
192.168.5.33/27
?
Answer : C
82
- Given the choices below, which address
represents a unicast address?
A.
B.
C.
D.
E.
224.1.5.2
FFFF. FFFF. FFFF.
192.168.24.59/30
255.255.255.255
172.31.128.255/18
Answer : E
83
Layer 3 devices
Router :
- Best path determination
- Creating routing table
- Connecting different LANs
- Network traffic filtration
- Quality Of Serves .
84
Find number of broadcast domains and number
of collision domains
Solution :
no. of broadcast domains = 2
no. of collision domains
=4
85
86
Operating Cisco IOS Software
87
87
Cisco Software components
• Cisco IOS (Internetwork Operating System)
 It is the operating system that manages the hardware
platform it is working on.
• Configuration File
 It is a program file that contains commands that
reflect how the router will react.
88
Router Internal Components
89
An Overview of Cisco Device Startup
90
Step in Router Initialization
91
External Components of a 2600 Router
92
Computer/Terminal Console Connection
93
HyperTerminal Session Properties
94
Setup mode
- Permit the administrator to install a minimal configuration for a router
( appeared if no saved configuration , Ctrl-C to skip )
95
Other Router Modes
96
IOS Features
• Support context help and abbreviations ( ? )
• Support of auto complete ( Tab button )
• Support syntax error detection
97
Context help features
98
Configuring Router Identification
99
Configuring a Router Password
100
Configuring Interfaces
S0/0
S0/1
192.168.1.2/30
192.168.1.1/30
Router#config t
RouterA(config)# interface serial 0/0
RouterA(config-if)# ip address 192.168.1.1 255.255.255.252
RouterA(config-if)# no shutdown
RouterA(config-if)# clock rate 56000
(required for serial DCE only)
RouterA(config-if)# bandwidth 64
(a value in kbps)
RouterA(config-if)# exit
RouterB(config)# int serial 0/1
RouterB(config-if)# ip address 192.168.1.2 255.255.255.252
RouterB(config-if)# no shutdown
RouterB(config-if)# exit
RouterB(config)# exit
Router#
To know which interface is the DCE :
RouterA# show controller s0/0
101
monitoring and debugging
show commands are typed in both privileged EXEC and user EXEC modes
#show interfaces
– Displays all the statistics for all the interfaces
#show int s0/1
– Displays statistics for interface Serial 0/1
#show ip interface brief
– Displays a summary about interfaces
#show flash
– Displays info about flash memory and what IOS in it
#show start
– Displays the saved configuration located in NVRAM
#show run
– Displays the configuration currently running in RAM
#show version
– Displays info about the router and the IOS
#show ARP
– Displays the ARP table of the router
#show protocol
– Displays the global and interface specific status of any
configured Layer 3 protocols
#show controllers serial0/0
#erase nvram
#reload
#copy run start
– Displays information-specific to the
interface hardware
– erase the saved configuration file
– restart the router
– save the current configuration in RAM into the NVRAM102
show version Command
103
Configuration Register Values
The configuration register value set the boot option
0x2100
0x2101
0x2102 to
0x210F
The value 0x2142 is used to bypass the NVRAM
104
Boot system command
- beside the configuration register you can
use the boot system command to force
booting location.
Router(config)# boot system flash
Router(config)# boot system rom
Router(config)# boot system tftp
105
show flash command
106
show running-config and
show startup-config Commands
• Displays the current and saved configuration
107
show interfaces Command
108
Interpreting the Interface Status
S0/1
S0/0
Interface
is working
properly
Layer 1 status
Layer 2 status
Other interface status :
- Serial0/1 is administratively down , line protocol is down
interface is shut down
- Serial0/1 is down , line protocol is down
interface or cable H/W failure ( no keep-alives )
- Serial0/1 is up , line protocol is down
different encapsulation type ( PPP , HDLC , FR ) or no clock rate
on the DCE device.
109
Serial Interface show controller
Command
• Shows the cable type of serial cables
110
Discovering Neighbors with CDP
• CDP runs on routers with Cisco IOS
to get information about the direct
connected Cisco devices.
• Summary information
includes:
– Device identifiers
– Address list
– Port identifier
– Capabilities list
– Platform
111
Using the show cdp
neighbors Command
RouterA# show cdp neighbors detail
provide also the neighbors ip addresses.
112
Using Telnet to Connect to
Remote Devices
Telnet is used to check all the TCP/IP stack
113
Using the ping and trace
Commands
Ping commands tests the connectivity and path to a remote device
( test layer 3 in TCP/IP )
114
Cisco IOS copy Command
To save IOS image or
configuration file
#
#
#
#
#
#
115
116