1 2 Networks Fundamentals Based On Cisco Systems.

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Networks Fundamentals Based On Cisco Systems

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Course Introduction

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Cisco Career Certifications

Professional

CCIE

CCNPCCNP

CCNACCNAAssociate

http://www.cisco.com/go/certifications

Recommended Training Through Cisco Learning Partners

Required Exam

CCNA

INTRO and ICND

Cisco Certified Network Associate

Introduction to Cisco Networking Technologies and Interconnecting Cisco Network Devices

Expert

CCNA Exam 640-801

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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

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• 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 informationSharing of expensive devices and network resourcesModern Technologies (IP telephony, Video on Demand, ….etc)

Networking Technologies

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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

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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

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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

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Reference Models

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Application

Transport

Internet

Network Access

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OSI Model OverviewOSI Model Overview

Data Flow Layers

Transport Layer

Data Link

Network Layer

Physical

Application (Upper) Layers

Session

Presentation

Application

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The OSI Reference model

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

transmission example

AB

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

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Encapsulation Process

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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

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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

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Layer 5 - The Session Layer

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Establishes, manages, and terminates sessions between two communicating hosts.

Example: Client Software

( Used for logging in)

PDU - Formatted Data

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Layer 4 - The Transport Layer

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

-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

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Layer 3 - The Network Layer

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

-Logical addressing (IP address)

- Selects the best Path Determination (routing)

PDU - Packets

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Layer 2 - The Data Link Layer

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

- provides reliable transit of data across a physical link hop by hop

- Makes decisions based on physical addresses (usually MAC addresses)

- Provides error detection PDU - Frames

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Layer 1 - The Physical Layer

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

This is the physical media through which the data, represented as electronic signals, is sent from the source host to the destination host.

Examples: UTP Coaxial (like cable TV) Fiber optic

PDU - Bits

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TCP/IP model

Application

Transport

Internet

Network Access

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

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Hierarchical Network Model

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The Physical Layer

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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

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LAN Physical Layer

Ethernet cables :

- Copper ( UTP , STP , Coaxial )- Fiber

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Unshielded Twisted Pair (UTP) Cable

CAT5 CAT 5e , CAT6

RJ-45

prevents EMI , RFI

to avoid attenuation

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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

PC

router

switch

hub

modem

Cross cable

straight cable

Cross 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 .

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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

Hubs takes data bits from input port and forward it to all other ports

A Hub is a multi-port Repeater

repeater and hub work in half duplex mode

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The Data-Link Layer

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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

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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)

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• Transparent Bridge and Switches has 3 main functions Address learningForward/filter decisionLoop avoidance

Ethernet Switches and Bridges

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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 segmentation

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Store and ForwardComplete frame is received and checked before forwarding.

Forwarding modes

Cut-Through• Switch checks destination

address and immediately begins forwarding frame.

Fragment-Free • Switch checks the first 64 bytes, then

begins forwarding frame.

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3 -Remove Layer 2 loops

MAC port

A

A

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1• Solution : using Spanning tree protocol (STP)

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Frame creation

Destination MAC

Source MAC

Source IP

Destination IP

Burnedon the NIC

-ARP

-Proxy ARP

-Static

-Dynamic (RARP , BOOTP ,

DHCP)

DNS

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-Source MAC

Burnedon the NIC

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-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.

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-Destination IP

• Application specified in the TCP/IP suite

• Means to translate human-readable names into IP addresses

DNS:

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-Destination MAC

- ARP :

-each PC form an ARP table containing the learned MAC’s

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-Destination MAC

A

Router R

Broadcast Message to all:If your IP address matches “B”

then please tell me your Ethernet address

B

A

B

Yes, I know the destinationnetwork, let me give you my

Ethernet address

I take care, to forwardIP packets to B

-Proxy ARP:

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The Transport Layer

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The Transport Layer

reliable service

unreliable service

Flow Control- Windowing (PAR):

2error in

22 2

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Flow Control- Windowing (PAR):

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Multiplexing applications

12.0.0.1

12.0.0.213.0.0.1

web server

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13.0.0.112.0.0.1 1200 801

13.0.0.112.0.0.1 1500 80

13.0.0.112.0.0.2 1200 80

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Source IP Destination IP Source port Destination port

TCP Header

UDP Header

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The Application Layer

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• File transfer

– FTP

– TFTP

• E-mail

– Simple Mail Transfer Protocol

• Remote login

– Telnet

• Network management

– Simple Network Management Protocol

• Name management

– Domain Name System

TCP/IP Application Layer Overview

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Port Numbers

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The TCP/IP Internet Layer

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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 ,

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IP (Internet Protocol)

• IP has the following characteristics

Provide Logical addressing

Provide connectionless “best effort” delivery of data

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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. ex. 192.168.1.3

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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 MulticastingClass E for Experimental purposes

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Identifying Address Classes

Note : for Class A , networks 0 & 127 are reserved (class A range 1 - 126)

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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.

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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.

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IP address types

• IP address could be one of three categories

Network address Host address Broadcast address

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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 - 2- Here are some examples:

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

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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 Network Address Default subnet mask A 12.0.0.0 255.0.0.0 or /8 B 172.16.0.0 255.255.0.0 or /16 C 192.168.0.0 255.255.255.0 or /24

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Octet Values of a Subnet Mask

• Subnet masks like IP addresses can be represented in the dotted decimal format like 255.255.255.0.

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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

Network part Host part

Subnet bits

Network part Host part

IP address

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Subnetting Example

Divide network 192.168.1.0/24 into 4 subnetsSolution: 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 /26The first subnet is 192.168.1.0/26

The second subnet is 192.168.1.64/26The third subnet is 192.168.1.128/26The fourth subnet is 192.168.1.192/26

0 - 63

64 - 127

128 - 191

192 - 255

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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

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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 172.16.6.0/23So 172.16.5.0/23 is a host address

172.16.5.0/23

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-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 . 192.168.5.75 192.168.5.33/27?

A

B

Answer : C

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-Given the choices below, which address represents a unicast address?

Answer : E

A . 224.1.5.2B . FFFF. FFFF. FFFF.

C . 192.168.24.59/30D . 255.255.255.255E . 172.31.128.255/18

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Layer 3 devices

Router :- Best path determination

- Creating routing table

- Connecting different LANs

- Network traffic filtration

- Quality Of Serves .

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Find number of broadcast domains and numberof collision domains

Solution:

no. of broadcast domains = 2

no. of collision domains = 4

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Operating Cisco IOS Software

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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.

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Router Internal Components

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An Overview of Cisco Device Startup

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Step in Router Initialization

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External Components of a 2600 Router

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Computer/Terminal Console Connection

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HyperTerminal Session Properties

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Setup mode

-Permit the administrator to install a minimal configuration for a router ( appeared if no saved configuration , Ctrl-C to skip )

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Other Router Modes

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IOS Features

• Support context help and abbreviations ( ? )

• Support of auto complete ( Tab button )

• Support syntax error detection

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Context help features

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Configuring Router Identification

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Configuring a Router Password

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Configuring Interfaces

Router#config tRouterA(config)# interface serial 0/0RouterA(config-if)# ip address 192.168.1.1 255.255.255.252RouterA(config-if)# no shutdownRouterA(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 192.168.1.2 255.255.255.252RouterB(config-if)# no shutdownRouterB(config-if)# exitRouterB(config)# exitRouter#To know which interface is the DCE :RouterA# show controller s0/0

S0/0S0/1

192.168.1.1/30192.168.1.2/30

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monitoring and debuggingshow 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 – Displays information-specific to the interface hardware#erase nvram – erase the saved configuration file#reload – restart the router#copy run start – save the current configuration in RAM into the NVRAM

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show version Command

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Configuration Register Values

0x2100

0x2101

0x2102 to 0x210F

The configuration register value set the boot option

The value 0x2142 is used to bypass the NVRAM

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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

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show flash command

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• Displays the current and saved configuration

show running-config and show startup-config Commands

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show interfaces Command

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Interpreting the Interface Status

Layer 1 status Layer 2 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.

Interface is working properly

Other interface status:

S0/1 S0/0

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• Shows the cable type of serial cables

Serial Interface show controller Command

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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

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Using the show cdp neighbors Command

RouterA# show cdp neighbors detail

provide also the neighbors ip addresses.

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Using Telnet to Connect to Remote Devices

Telnet is used to check all the TCP/IP stack

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Using the ping and trace Commands

Ping commands tests the connectivity and path to a remote device( test layer 3 in TCP/IP )

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Cisco IOS copy Command

#

#

#

#

#

#

To save IOS image or configuration file

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