Ccna Slides

Networking Basics

How a LAN Is Built

1999, Cisco Systems, Inc.www.cisco.com

Local-Area NetworkLAN

What is a LAN? A collection of computers, printers, and other

devices that can communicate with each other in a small area (< ~ 3000 m or 1000 feet)

What are the components? Computers, operating system (OS),

network interface card (NIC), and hubs

How is a LAN controlled? ProtocolsFormal descriptions of sets of rules and

conventions that govern how devices on a network exchange information

Local-Area Networks

LANs are designed to:

Operate within a limited geographic area

Allow multi-access to high-bandwidth media

Control the network privately under local administration

Provide full-time connectivity to local services

Connect physically adjacent devices

Network Operating System (OS)

Software that allows communicating and sharing of data and network resources

Examples: AppleTalk

NetWare

Win NT

PC or Workstation

Loaded with NOS

Connector Port

PC or Workstation

Loaded with NOS

Network Interface

Card (NIC)

Network Interface Card

Amplifies electronic signals

Packages data for transmission

Physically connects computer to transmission media (cable)

1990sGlobal Internetworking

19921 major backbone, 3,000 networks, 200K computers

1995Multiple backbones, hundreds of regional nets, tens of thousands

of LANs, millions of hosts, tens of millions of users

Doubling every year!

The OSI Model

OSI Layer is meant for Networking manufacturers and developers to provide them a standard based on which they can make their products.

All OSI Layers are independent from each other, which makes introducing changes easier as no other layers are effected.

Ease of Troubleshooting.

The Layered Model

1999, Cisco Systems, Inc. www.cisco.com

Layered Communication

Source: Tanenbaum, 1996

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Message

Information

for the

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Information

for the

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Location A


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Information

for the

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Information

for the

Remote

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Location A Location B

Message


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Information

for the

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for the

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secretary

Location A Location B

1

2

3

Layers

Message

Why a Layered Network Model?

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Reduces complexity (one big problem to seven smaller ones)

Standardizes interfaces

Facilitates modular engineering

Assures interoperable technology

Accelerates evolution

Simplifies teaching and learning

Devices Function at Layers

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

NIC Card

Hub

Host Layers

7 Application

6 Presentation

5 Session

4 Transport

Network

3 Data Link

1

Host layers: Provide accurate data delivery

between computers}Physical

Media Layers

7 Application

6 Presentation

5 Session

4

Transport

3 Network

2 Data Link

1 Physical

Host layers: Provide accurate data delivery

between computers

Media layers: Controlphysical delivery of messages

over the network}}

Layer Functions

Provides network services to

application processes (such as

electronic mail, file transfer, and

terminal emulation)

7 Application

Layer Functions

Network services to applications

Ensures data is readable by receiving system

Format of data Data structures Negotiates data transfer

syntax for application layer

7 Application

6 Presentation Data representation

Layer Functions

Inter-host communication

Establishes, manages, and terminates sessions between

applications

7 Application

6 Presentation

5 Session


Data representation

Layer Functions

7 Application

6 Presentation

5 Session

Transport4



Data representation

End-to-end connection reliability Concerned with data transport

issues between hosts

Data transport reliability Establishes, maintains, and

terminates virtual circuits

Fault detection and recovery Information flow control

Layer Functions

7 Application

6 Presentation

5 Session

Transport4

Network3



Data representation

End-to-end connection reliability

Addresses and best path Provides connectivity and path

selection between two end

systems

Domain of routing

Layer Functions7 Application

6 Presentation

5 Session

Transport4

Network3

Data Link2



Data representation


Addresses and best path

Access to media Provides reliable transfer of data

across media

Physical addressing, network topology, error notification, flow

control

Layer Functions

7 Application

6 Presentation

5 Session

Transport4

Network3

Data Link2

Physical1



Data representation


Addresses and best path

Access to media

Binary transmission

Wires, connectors, voltages, data rates

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Host A

Peer-to-Peer Communications

Application

Presentation

Session

Transport

Network

Data Link

PhysicalBits

Frames

Packets

Segments

Host B

Application Layer

This is where users communicate to the computer.

This is where communication between two users are established.

This is a point where user or application interfaces with the protocols to gain access to the network.

Examples are WWW, Telnet, FTP, TFTP, E-mail, SNMP, DNS

Presentation Layer

Tasks like Translation, Encryption, decryption, compression, decompression are associated with this layer.

It receives the data in native format & converts in standard format or receives data in standard format and converts in native format, ie. EBCDIC to ASCII.

It is mainly responsible for how the data is to be presented to the Application Layer.

Examples are PICT, TIFF, JPEG, MIDI, MPEG, GIFF etc.

Presentation Layer

ASCIIEBCDIC

Encrypted

Text

Data

login:

PICTTIFF

JPEGGIF

Graphics

Visual images

Sound

VideoMPEG

QuickTime

MIDI

Provides code formatting and conversion for applications

Session Layer

Session EstablishmentEstablishes a session between two devices before actual transmission of data.

Dialog ControlSimplex

Half Duplex

Full Duplex

Simplex

Data travels only one way.

Radio transmission is the best example of this.

Half Duplex

Both way but one at a time. By default all LAN Cards (NICs) work on Half Duplex.

Full Duplex

Both way at the same time.

Session Layer

Session Layer

Network File System (NFS)

Structured Query Language (SQL)

Remote-Procedure Call (RPC)

X Window System

AppleTalk Session Protocol (ASP)

DEC Session Control Protocol (SCP)

Service Request

Service Reply

Coordinates applications as they interact on different hosts

Transport Layer

Segments upper-layer applications

Establishes an end-to-end connection

Sends segments from one end host to another

Optionally, ensures data reliability

Transport Layer

Transport Layer never actually transports the data but only prepares for transporting.

Uses Socket to define the services running on a particular node, the data is associated with.

Responsible for the following :

Segmentation

End-to-end Communication

Flow Control

Error Control

Multiplexing of Applications

TCP, UDP and SPX work at this layer

Socket Socket is a software component and points to a particular service running

on a particular node.

Structure of a socket

IP Address + Port Address

Each service has a unique Port address

Max. Port Addresses can be 65,536

Port address 1-1023 is reserved for specific Services like

WWW - 80

FTP - 21

SMTP - 25

Port Addresses are reserved for standardization purpose.

Transport LayerSegments Upper-Layer

Applications

Electronic

Mail

File

Transfer

Application

Presentation

Session

Segments

DataApplication

Port

Transport DataApplication

Port

Terminal

Session

Port Numbers

TCP

Port

Numbers

FTP

Transport

Layer

TELNET

DNS

SNMP

TFTP

SMTP

UDP

Application

Layer

21 23 25 53 69 161

RIP

520

Segmentation

This is a mechanism wherein the data is divided into multiple segments and sent over the network.

By doing this different segments can use different links for travelling across the network.

If one segment is lost the only segment is required to be re-sent and not the entire data.

Once all segments reach to the destination the received segments have to be sequenced back, which is also done at

this layer.

Transport LayerSends Segments with Flow Control

Transmit

Buffer FullNot Ready

StopProcess

Segments

Buffer OKReadyGo

Resume Transmission

ReceiverSender

Flow Control

Used while connection oriented communication

It helps to have a control on over flow of Buffer.

Advantages are:

The segments delivered are acknowledged if received

Any segment not acknowledged are retransmitted

segments are sequenced back upon their arrival

Congestion, Overloading and data loss are avoided

To achieve all this it uses the technique of Sliding window or Windowing

Transport LayerEstablishes Connection

Synchronize

Synchronize

Acknowledge

Negotiate Connection

Receiver

Data Transfer

Connection Established

(Send Segments)

Sender

End-to-End Communication

Connection Less Transmission UDP is used

Not reliable

Faster

Connection Oriented Transmission TCP or SPX is used

Reliable

Slower

Connection Oriented Protocol

These protocols relies on Acknowledgement.

Positive acknowledgement means data has been received.

Negative acknowledgement means data is lost no further data is sent till positive acknowledgement is received.

It is slow but Reliable.

Eg. TCP and SPX

Transport LayerReliability with Windowing

Window Size = 1

Sender

Send 1 Receive 1

Receiver

Ack 2

Send 2 Receive 2

Ack 3

Sender

Send 1

Send 2Receive 1Receive 2

Receiver

Window Size = 3

Send 3 Receive 3Ack 4

Send 4

Transport LayerAn Acknowledgement Technique

Sender Receiver

Send 2Send 1

Send 3

Ack 4

Send 5Send 4

Send 6

Ack 5

Send 5Ack 7

1 2 3 4 5 6 7 1 2 3 4 5 6 7

Connection Less Protocol

They do not provide acknowledgement neither sequence numbers.

It is faster but not reliable

Eg. UDP

Network Layer

It is responsible for communicating Networks

It recognizes Networks with the help of Netwok Addresses

Network Address is a logical address like IP Address or IPX Address

It is common for a group of computers

It works only with Network IDs and has got nothing to do with host Ids.

Path determination or Routing is performed at this layer.

Router works at this layer.

Network Layer: Path

Determination

Which Path?Which Path?

Layer 3 functions to find the best path through the internetwork

Network Layer: Communicate

Path

1

2

3

4

5

6

7

8

9

10 11

Addresses represent the path of media connections

AddressingNetwork and Node

Network Node

1

2

123

1

3 1

1.1

2.1

3.1

1.2

1.3

Network addressPath part used by the router

Node addressSpecific port or device on the network

Protocol Addressing Variations

Network Node

1 1

General

Example

Network Host

10. 8.2.48

TCP/IP

Example(Mask 255.0.0.0)

Network Node

1aceb0b. 0000.0c00.6e25

Novell IPX

Example

Network Layer

Protocol Operations

Each router provides its services to support upper layer functions

X Y

AA

CC

Routed Versus Routing Protocol

Routed protocol

used between

routers to direct

user traffic

Examples: IP, IPX,

AppleTalk

Routing protocolused only between

routers to maintain

routing tables

Examples: RIP, IGRP, OSPF

Static Versus Dynamic Routes

Uses a protocol route that a network

administrator enters into the router

Static Route

Uses a route that a network protocoladjusts automatically for topology or

traffic changes

Dynamic Route

Static Route Example

Point-to-point orcircuit-switched

connection

Stub network

Only a single network

connection with no need

for routing updates

AA

BB

Fixed route to address reflects administrators knowledge

Adapting to Topology Change

AA BB

CCDD

Can an alternate route substitute for a failed route?


AA BB

CCDD

XX


AA BB

CCDD

XX

Can an alternate route substitute for a failed route?

YesWith dynamic routing enabled

Data Link Layer

It uniquely identifies each device in the Network.

It translates data from Network Layer into bits for the Physical layer to transmit.

It formats the messages into Data Frames

Adds a customized header containing Source and Destination hardware address

This layer works with Frames

This layer is logically divided in two sub-layers:

LLC (Logical Link Control)

MAC (Media Access Control)

Physical Layer

Electrical and Mechanical settings are provided at this layer.

Transmits data in the form of bits.

This layer communicates directly with actual communication media.

At this layer DCE & DTE are identified

DCE (Data Circuit-Terminating Equipment)

Located at Service Providers side

DTE (Data Terminal Equipment)

The attached device at customer Place eg. Modem

Services available to a DTE is most often accessed via a Modem or Channel Service Unit (CSU) Data Service Unit (DSU).

HUBs & REPEATERS are working at this layer.

Max. troubleshooting occurs at this layer.

DOD MODEL

The DoD Model The Process / Application Layer

The Host-to-Host Layer

The Internet Layer

The Network Layer

The DoD & OSI

Application

Application

Presentation

Session

Transport

Network

Data Link

Physical

Host-to-Host

Internet

Network

Access

DoD Model OSI Model

Process/Application Layer

The Process / Application layer defines protocols for node-to-node application communication and

also controls user-interface specification.

A vast array of protocols combine at this layer of DoDs Model to integrate the activities and duties of upper layer of OSI.

Examples for this layer are :

Telnet, FTP, TFTP, NFS, SMTP, SNMP, DNS

DHCP, BootP etc.

Host-to-Host Layer

The Host-to-Host layer parallels the functions of the OSIs Transport layer

It performs the following:

Defining protocols for setting up the level of transmission service for Applications

It tackles issues like creating reliable ene-to-end communication.

It ensures the error free delivery of data

It handles packet sequencing and maintains data integrity.

Internet Layer

Internet Layer corresponds to the OSIs Network Layer.

It performs the following:

Designating the protocols relating to the logical transmission of packets over the entire network.

It takes care of the addressing of hosts by giving them an IP address.

It handles routing of packets among multiple networks.

Network Access Layer

This layer is equivalent of the Data Link and Physical Layer of OSI model.

It performs the following It monitors the data exchange between the host and

the network.

Network Access Layer overseas hardware addressing and defines protocols for the physical transmission of the Data.

Lets have a look on how TCP/IP Protocol suit relates to the DoD model layers.

TCP/IP Protocol Suit at DoD

DoD Model

Process /

Application

Host-to-Host

Internet

Network

Access

TCP/IP Protocol Suit

Telnet FTP LPD SNMP

X WindowNFSSMTPTFTP

TCP UDP

ICMP

Ethernet

ARP RARP

IP

Fast

Ethernet

Token

Ring FDDI

BootP

LOWER LAYERS

PROTOCOLS

Common LAN Technologies

Ethernet

Token Ring

FDDIFDDI

Dual Ring

TokenRing

Ethernet

1999, Cisco Systems, Inc. www.cisco.com

Introduction

Ethernet is a methodology for accessing a media

It allows all hosts on a network to share the same bandwidth of a link.

It is popular because :

It is easy to implement & Troubleshoot

It is easy to add new technologies like Fast Ethernet and Gigabit Ethernet to existing infrastructure.

Ethernet uses Data Link Layer and Physical Layer Specification

It uses something called CSMA/CD

Ethernet Operation

AA BB CC DD

Ethernet Operation

AA BB CC DD

D

Data Link

Network

Transport

Session

Presentation

Application

Physical

Ethernet Operation

AA BB CC DD

D

Data Link

Network

Transport

Session

Presentation

Application

Physical

B and C

Data Link

Network

Transport

Session

Presentation

Application

Physical

Ethernet LANs:How do they work?

Multiple workstations are connected to a

segment

Each station has to take turns sending traffic

All stations listen to all traffic on their segment

Stations can only send data (Ethernet Frames)

when no one else is

sending

Ethernet LANs:MAC Addresses

Every workstation has a Network Interface

Card (NIC)

Every NIC has a unique MAC address

Stations use MAC addresses to send

Ethernet Frames to a

specific station

0000.0c12.3456

0000.0c12.11110000.1018.321a

Ethernet LANs:Unicast Frames

Ethernet frames contain the MAC address of the

station that the frame

was sent to

These are called unicast frames

All stations receive the Ethernet frame, but

ignore the frames that

are not addressed to

their MAC address

0000.0c12.3456

0000.0c12.11110000.1018.321a

Frame

To: 0000.0c12.3456

Ethernet LANs:Broadcast Frames

Some Ethernet frames are sent to all stations

These are called broadcast frames

All stations process this frame

0000.0c12.3456

0000.0c12.11110000.1018.321a

Frame

To: FFFF.FFFF.FFFF

Flow Control Mechanism

on Ethernet

CSMA/CD is the mechanism that

regulates the segment

Each station listens for other traffic before they

transmit

PacketFrame

Ethernet Collisions

Sometimes stations transmit simultaneously

Two frames on the same segment collide

Collisions require each station to wait and resend

Collision!

PacketFrame PacketFrame

Packe

t

Packe

tFrameFrame

Ethernet Reliability

B C DA

B C DAFigure 1

Figure 2

Collision


Collision

C

B C DA

BA D

JAMJAMJAMJAMJAM JAM


B C DA

Collision

B C DA

JAMJAMJAMJAMJAM JAM

Carrier sense multiple access with collision detection (CSMA/CD)

CSMA/CD CSMA/CD stands for Carrier Sense Multiple Access /

Collision Detect.

It is used by all NICs in Ethernet Networking

In this method all NICs first sense whether the cable is free or not.

If it is free the request is sent otherwise it waits.

Half Duplex Ethernet

It is defined in 802.3 Ethernet specifications

It uses only one wire pair for signals running in both direction.

CSMA/CD is used to prevent collision.

Half Duplex typically 10base T is 50-60 % efficient. (In CISCO views)

In a large 10 base T network you only get 3 to 4 MBPS at most.

Full Duplex

Full Duplex Ethernet uses two pairs of wires.

It uses Point-to-Point connection

There is no collision in Full Duplex

Full Duplex is suppose to offer 100% efficiency in both direction

Means you can get 20 MBPS in 10 MBPS or 200 MBPS in Fast Ethernet running Full

Duplex.

Auto Detect Mechanism

When a Full Duplex port is powered on, it first checks with remote end and decides whether it can run on 10 or 100 MBPS.

Then it checks to see whether it can run Full duplex or half duplex.

This is called Auto Detect Mechanism.

Ethernet Addressing Ethernet Addressing uses MAC Address

MAC addresses are burned on every NIC

It is a 48-bit address

It is written in the same format even if different LAN Technologies are used.

Organizationally

Unique Identifier (OUI)

(Assigned by IEEE)

Vender Assigned

24 bits 24 bits

Ethernet Addressing using MAC Addresses

Ethernet and IEEE 802.3

Benefits and background

Ethernet is the most popular physical layer LAN technology because it strikes a good balance between speed, cost, and ease of installation

Supports virtually all network protocols

Xerox initiated, then joined by DEC & Intel in 1980

Revisions of Ethernet specification

Fast Ethernet (IEEE 802.3u) raises speed from 10 Mbps to 100 Mbps

Gigabit Ethernet is an extension of IEEE 802.3 which increases speeds to 1000 Mbps, or 1 Gbps

Ethernet and IEEE 802.3

Several framing variations exist for this common LAN technology

Ethernet Frames

Frames are used at the Data Link Layer to encapsulate packets coming down for transmission on a type of Media Access

Types of Media Access Contention (Ethernet)

Token Passing (Token Ring or FDDI) We will be covering only Contention, as rest all are beyond the scope of our course.

DataSource add FCSLengthDest add

Variable266 4

0000.0C xx.xxxx

Vendor assigned

IEEE assigned

MAC Layer - 802.3

MAC SUB-LAYER

Preamble

Ethernet II

uses Type here and

does not use

802.2.

MAC Address

8# Bytes

Preamble

It allows the receiving devices to lock the incoming bit stream.

The Peamble is used to indicate to the receiving station that the data portion of

the message will follow.

Destination Address (DA)

DA is used by receiving stations to determine if an incoming packet is addressed to a particular node.

Uses LSB (Least Significant Bit) first

Destination can be individual, multicast or broadcast Broadcast will be all 1s or Fs and will be sent to

all.

Multicast will be sent to the specific subnet

Source Address (SA)

SA is a 48 bit MAC Address supplied by the transmitting device.

Broadcast and Multicast address formats are illegal within the SA fields.

It uses LSB (Least significant bit first)

Length or Type Field

802.3 uses length field where as Ethernet frame uses type field to identify the network layer

protocol.

802.2 can identify upper-layer protocol and must be used with 802.3 frame.

Data

This is the packet sent down to the Data Link Layer from the Network layer.

The size can vary from 46-1500 bytes.

Frame Check Sequence (FCS)

FCS is a field at the end of the frame that is used to store the cyclic redundancy

check.

DataDest

SAP

Source

SAP

DataSource add FCSLengthDest add

Variable11

802.2 (SAP)

MAC Layer - 802.3

Data Link Layer Functions (cont.)

Ctrl

1 or 2

3 2

Preamble

DataDest SAP

AASource SAP

AA

Variable11

802.2 (SNAP)

Ctrl

03

1 or 2

OR

OUI

IDType

# Bytes

# Bytes

802.2 Frame

802.2 Frame has two new fields DSAP (Destination Service Access Pointer)

SSAP (Source Service Access Pointer)

802.2 frame type is nothing but 802.3 frame with LLC information

Because of the LLC information we know what upper layer protocol is.

SNAP Frame The SNAP Frame has its own protocol field to identify

the upper layer protocol. To Identify SNAP Frame:

DSAP and SSAP fields are always AA to indicate that this is a SNAP header coming up.

it is an LLC data unit (sometimes called a Logical Protocol Data Unit (LPDU)) of Type 1 (indicated by 03)

The SNAP header then indicates the vender via the Organisational Unique Identifier (OUI) and the protocol type via the Ethertype field

CISCO uses SNAP frame with their proprietary protocol CDP (CISCO Discovery Protocol)

EXAMPLE - SNAP

In the example above we have the OUI as

00-00-00 which means that there is an Ethernet

frame, and the Ethertype of 08-00 which

indicates IP as the protocol.

ETHERNET

CABLING

Network Cabling

Media connecting network components NIC cards take turns transmitting on the cable

LAN cables only carry one signal at a time

WAN cables can carry multiple signals simultaneously

Three primary types of cabling Twisted-pair (or copper)

Coaxial cable

Fiber-optic cable

Twisted-Pair (UTP and STP)

Speed and throughput: 10/100 Mbps

Relative cost: Least costly

Media and connector size: Small

Maximum cable length: 100 m

RJ-45

Connector

Color-Coded

Plastic Insulation

Twisted-Pair

Outer Jacket

STP only:

Shielded Insulation

to Reduce EMI

Coaxial Cable

Speed and throughput: 10/100 Mbps

Relative cost: More than UTP, but still low

Media and connector size: Medium

Maximum cable length: 200/500 m

OuterJacketBraided Copper Shielding

Plastic Insulation

Copper Conductor

BNC Connector

Fiber-Optic Cable

Outer JacketKevlar Reinforcing

Material

Plastic

Shield Glass Fiber

and Cladding

Speed and throughput: 100+ Mbps

Average cost per node: Most expensive

Media and connector size: Small

Maximum cable length: Up to 2 km

Optical Fiber

Metal cables transmit signals in the form of electric current

Optical fiber is made of glass or plastic and transmits signals in the form of light.

Light, a form of electromagnetic energy, travels at 300,000 Kilometers/second ( 186,000 miles/second), in

a vaccum.

The speed of the light depends on the density of the medium through which it is traveling ( the higher

density, the slower the speed).

Ethernet Local Area Network Ethernet was first created and implemented by a group called

DIX (Digital, Intel and Xerox).

The first Ethernet specification was modified by IEEE and IEEE 802.3 was created.

This was a 10Mbps network running on co-axial, twisted pair and fiber physical media.

IEEE 802.3 was further modified by IEEE only and 802.3u (Fast Ethernet) and 802.3g (Gigabit Ethernet) was created.

802.3u and 802.3g are specified only on twisted pair and fiber physical media.

LAN

speed (bps)

100BaseFX

Base = basebandBroad = broadband

Indicates type of cable

and maximum length.

If a number,

max. length = # x 100 m

Ethernet Protocol Names

Cable Specification

Cables Distance Throughput EthernetStandard

Connectors

Co-axialThinnet

185 Mtrs. 10 MBPS 10Base2 T-connector

Co-axialThicknet

500 Mtrs. 100 MBPS 10Base5 AUI

Category 3 100 Mtrs. 10 MBPS 10BaseT RJ-45

Category 5 100 Mtrs. 100 MBPS 10BaseX /Fast Ethernet

RJ-45

UTP Connections (RJ-45) UTP Cables have eight colored wire.

These wires are twisted into 4 pairs

Four (two pairs) carry the voltage and are considered tip.

The more twists per inch in the wire, the less interference.

CAT 5 & 6 have many more twists per inch than CAT 3 UTP.

Crimping There are two types of Crimping used with UTP cables and

RJ-45 connectors. Straight-Through

This is used while connecting Router to a Hub or Switch Server to Hub or Switch Workstation to a Hub or Switch

CrossoverThis is used while connecting Uplinks between Switches Hubs to Switches Hub to another Hub Router Interface to another Router Interface

UTP Implementation

Straight-through

Wires on cable ends are in same order

Pin Label

1 RD+

2 RD-

3 TD+

4 NC

5 NC

6 TD-

7 NC

8 NC

Cable 10BaseT/100BaseTx Straight-through

Pin Label

1 TD+

2 TD-

3 RD+

4 NC

5 NC

6 RD-

7 NC

8 NC

Server/Router

81

wg

g bwo

wb

o brwbr

1

8

Straight-through Cable

8

1Hub/Switch

81

wg

g bwo

wb

o brwbr

UTP Implementation

Crossover

Some wires on cable ends are crossed

8 1

wo

ob wg

wb

gbr wbr

Cable 10BaseT/100BaseT Crossover

Pin Label

1 RD+

2 RD-

3 TD+

4 NC

5 NC

6 TD-

7 NC

8 NC

Pin Label

1 RD+

2 RD-

3 TD+

4 NC

5 NC

6 TD-

7 NC

8 NC

Crossover Cable

1

8 1

8

8 1

wg

gwb

wo

b obr wbr

Hub/Switch Hub/Switch

CISCO MODEL

118

Network Structure Defined by

Hierarchy

Distribution

Layer

Core Layer

Access

Layer

The Three Layers are :

Core Layer

Distribution Layer

Access Layer

120

Core Layer Characteristics

Fast transport to enterprise services

No packet manipulation

Core Layer

Core Layer is actually the core of the network.

It is responsible for transporting large amount of traffic reliably and quickly.

Core Layer failure affects each individual user, hence fault tolerance becomes an issue at this layer.

Core layer is likely to see large volume of traffic, hence speed and latency is the driving concerns.

There are few thing we do not want to do at core layer but few things are recommended to do at this layer.

Core Layer

122

Distribution Layer Characteristics

Access Layer Aggregation Point

Routes traffic

Broadcast/Multicast Domains

Media Translation

Security

Possible point for remote access

Distribution Layer

It is sometimes also referred as workgroup layer.

It is communication point between Access Layer and Core Layer.

Routing, Filtering & WAN Access is the Primary function of the distribution layer.

Network policies are implemented at Distribution Layer.

Best path is determined and request are forwarded to Core Layer.

Distribution Layer

At Distribution LayerWe do the following:

Implementation of tools like access lists, packet filtering etc.

Implementation of security and network policies like address translation and firewalls

Redistribution between routing protocols, including static routing

Routing between VLANs

Definition of Broadcast and Multicast Domains

125

Access Layer Characteristics

End station entry point to the network

Access Layer

The Access Layer Access Layer controls users and workgroup

access to network resources.

This layer is also referred to as Desktop Layer.

Continues access control and policies from distribution layer

Creation of separate collision domains (segmentation)

Workgroup connectivity into the distribution layer

UPPER LAYER PROTOCOLS

What Is TCP/IP?

A suite of protocols

Rules that dictate how packets of information are sent across

multiple networks

Addressing

Error checking

TCP/IP Protocol The Transmission Control Protocol/Internet Protocol

(TCP/IP) suit was created by the Department of Defense (DoD).

The Internet Protocol can be used to communicate across any set of interconnected networks.

TCP/IP supports both LAN and WAN communications.

IP suite includes not only Layer 3 and 4 specifications but also specifications for common applications like e-mail, remote login, terminal emulation and file transfer.

The TCP/IP protocol stack maps closely to the OSI model in the lower layers.

The DoD & OSI

Application

Application

Presentation

Session

Transport

Network

Data Link

Physical

Host-to-Host

Internet

Network

Access

DoD Model OSI Model

TCP/IP Protocol Suit at DoD

DoD Model

Process /

Application

Host-to-Host

Internet

Network

Access

TCP/IP Protocol Suit

Telnet FTP LPD SNMP

X WindowNFSSMTPTFTP

TCP UDP

ICMP

Ethernet

ARP RARP

IP

Fast

Ethernet

Token

Ring FDDI

BootP

TCP/IP Applications

Application layer File Transfer Protocol (FTP)

Remote Login (Telnet)

E-mail (SMTP)

Transport layer Transport Control Protocol (TCP)

User Datagram Protocol (UDP)

Network layer Internet Protocol (IP)

Data link & physical layer LAN Ethernet, Token Ring, FDDI, etc.

WAN Serial lines, Frame Relay, X.25, etc.

Internet Layer Overview

In the OSI reference model, the network layer corresponds to the TCP/IP Internet layer.

Internet Protocol (IP)

Internet Control MessageProtocol (ICMP)

Address ResolutionProtocol (ARP)

Reverse AddressResolution Protocol (RARP)

Application

Transport

Internet

Data-Link

Physical

Internet Protocol

Provides connectionless,best - effort delivery routing of datagrams.

IP is not concerned with the content of the datagrams.

It looks for a way to move the datagrams to their destination.

IP Datagram

Version

(4)

Destination IP Address (32)

Options (0 or 32 if Any)

Data (Varies if Any)

1Bit 0 Bit 15 Bit 16 Bit 31

Header

Length (4)Type

of Service (8)Total Length (16)

Identification (16)Flags

(3) Fragment Offset (13)

Time-to-Live (8) Protocol (8) Header Checksum (16)

Source IP Address (32)

20

Bytes

IP Datagram Version Currently used IP version

Header Length Datagram header length

TOS Level of importance assigned by a particular upper-layer protocol

Total Length- Length of packet in bytes including Data and Header

Identification Identifies current datagram (Sequence Number)

Flags Specifies whether the packet can be fragmented or not

Fragment Offset Used to piece together datagram fragments

TTL It maintains a counter that gradually decreases, in increments, to zero

Protocol It indicates which upper-layer protocol receives incoming packets

Header Checksum Calculated checksum of the header to check its integrity

Source IP Address Sending node IP Address

Destination IP Address Receiving node IP Address

Options It allows IP to support various options like security

Data Upper layer information (maximum 64Kb)

Determines destination upper-layer protocol

Protocol Field

Transport

Layer

Internet

Layer

TCP UDP

Protocol

Numbers

IP

176

Address Resolution Protocol

(ARP) ARP works at Internet Layer of DoD Model

It is used to resolve MAC address with the help of a known IP address.

All resolved MAC addresses are maintained in ARP cache table is maintained.

To send a datagram this ARP cache table is checked and if not found then a broadcast is sent

along with the IP address.

Machine with that IP address responds and the

MAC address is cached.


172.16.3.1 172.16.3.2

IP: 172.16.3.2 = ???

I need the

Ethernet

address of

176.16.3.2.


172.16.3.1 172.16.3.2

IP: 172.16.3.2 = ???

I heard that broadcast.

The message is for me.

Here is my Ethernet

address.

I need the

Ethernet

address of

176.16.3.2.


172.16.3.1

IP: 172.16.3.2

Ethernet: 0800.0020.1111

172.16.3.2

IP: 172.16.3.2 = ???



Here is my Ethernet

address.

I need the

Ethernet

address of

176.16.3.2.


Map IP Ethernet

172.16.3.1

IP: 172.16.3.2

Ethernet: 0800.0020.1111

172.16.3.2

IP: 172.16.3.2 = ???



Here is my Ethernet

address.

I need the

Ethernet

address of

176.16.3.2.

RARP (Reverse ARP) This also works at Internet Layer. It works exactly opposite of ARP

It resolves an IP address with the help of a known MAC addres.

DHCP is the example of an RARP implementation.

Workstations get their IP address from a RARP server or DHCP server with the help of RARP.

Reverse ARP

Ethernet: 0800.0020.1111 IP = ???

What is

my IP

address?

Reverse ARP

Ethernet: 0800.0020.1111 IP = ???

What is

my IP

address?

I heard that

broadcast.

Your IP

address is

172.16.3.25.

Reverse ARP

Ethernet: 0800.0020.1111

IP: 172.16.3.25

Ethernet: 0800.0020.1111 IP = ???

What is

my IP

address?

I heard that

broadcast.

Your IP

address is

172.16.3.25.

Reverse ARP

Map Ethernet IP

Ethernet: 0800.0020.1111

IP: 172.16.3.25

Ethernet: 0800.0020.1111 IP = ???

What is

my IP

address?

I heard that

broadcast.

Your IP

address is

172.16.3.25.

Bootstrap Protocol (BootP)

BootP stands for BootStrap Protocol.

BootP is used by a diskless machine to learn the following:

Its own IP address

The IP address and host name of a server machine.

The boot filename of a file that is to be loaded into memory and executed at boot-up.

BootP is an old program and is now called the DHCP.

DHCP (Dynamic Host Configuration Protocol)

The DHCP server dynamically assigns IP address to hosts.

All types of Hardware can be used as a DHCP server, even a Cisco Router.

BootP can also send an operating system that a host can boot from. DHCP can not perform this function.

Following information is provided by DHCP while host registers for an IP address:

IP Address

Subnet mask

Domain name

Default gateway (router)

DNS

Internet Control Message

Protocol

Application

Transport

Internet

Data-Link

Physical

Destination

Unreachable

Echo (Ping)

Other

ICMP

1

ICMP messages are carried in IP datagrams and used to send error and control messages.

ICMP Ping

Transport Layer Overview

Transmission ControlProtocol (TCP)

User Datagram Protocol (UDP)

Application

Transport

Internet

Data-Link

Physical

Connection-

Oriented

Connectionless

Transmission Control Protocol

(TCP)

TCP works at Transport Layer

TCP is a connection oriented protocol.

TCP is responsible for breaking messages into segments and reassembling them.

Supplies a virtual circuit between end-user application.

TCP Segment Format

Source Port (16) Destination Port (16)

Sequence Number (32)

Header

Length (4)

Acknowledgment Number (32)

Reserved (6) Code Bits (6) Window (16)

Checksum (16) Urgent (16)

Options (0 or 32 if Any)

Data (Varies)

20

Bytes

Bit 0 Bit 15 Bit 16 Bit 31

TCP Segment Format Source port Number of the calling port

Destination Port Number of the called port

Sequence Number Number used to ensure correct sequencing of the arriving data

Acknowledgement Number Next expected TCP octet

Header Length Length of the TCP header

Reserved Set to zero

Code Bits Control Functions (setup and termination of a session)

Window Number of octets that the sender is willing to accept

Checksum Calculated checksum of the header and data fields

Urgent Pointer Indication of the end of the urgent data

Options One option currently defined (maximum TCP segment size)

Data Upper layer protocol data

Port Numbers

TCP

Port

Numbers

FTP

Transport

Layer

TELNET

DNS

SNMP

TFTP

SMTP

UDP

Application

Layer

21 23 25 53 69 161

RIP

520

TCP Port Numbers

Source

Port

Destination

Port

Host A

1028 23

SP DP

Host ZTelnet Z

Destination port = 23.

Send packet to my

Telnet

application.

Send SYN (seq = 100 ctl = SYN)

SYN Received

Send SYN, ACK (seq = 300 ack = 101 ctl = syn,ack)

Established(seq = 101 ack = 301 ctl = ack)

Host A Host B

1

2

3

SYN Received

TCP Three-Way Handshake/Open

Connection

Window Size = 1

Sender Receiver

Send 1Receive 1

Receive ACK 2 Send ACK 2

Send 2Receive 2

Receive ACK 3Send ACK 3

Send 3Receive 3

Receive ACK 4 Send ACK 4

TCP Simple Acknowledgment

TCP Sequence and

Acknowledgment Numbers

Source

Port

Destination

Port

Sequence Acknowledgment

1028 23

Source Dest.

11

Seq.

2

Ack.

1028 23

Source Dest.

10

Seq.

1

Ack.

102823

Source Dest.

11

Seq.

1

Ack.

.

I just got number

10, now I need

number 11.

I just

sent number

10

Window Size = 3Send 2

TCP Windowing

Sender Window Size = 3Send 1


ACK 3Window Size = 2

Packet 3 Is

Dropped



ACK 5Window Size = 2

ReceiverWindow Size = 3

UDP (User Datagram

Protocol) A connectionless and unacknowledged protocol. UDP is also responsible for transmitting messages.

But no checking for segment delivery is provided.

UDP depends on upper layer protocol for reliability.

TCP and UDP uses Port no. to listen to a particular services.

No sequence or acknowledgment fields

UDP Segment Format

Source Port (16) Destination Port (16)

Length (16)

Data (if Any)

1Bit 0 Bit 15 Bit 16 Bit 31

Checksum (16)

8

Bytes

UDP Segment Format

Source port Number of the calling port

Destination Port Number of the called port

Length Number of bytes, including header and data

Checksum Calculated checksum of the header and data fields

Data Upper layer protocol data

Application Layer Overview

*Used by the Router

Application

Transport

Internet

Data-Link

Physical

File Transfer- TFTP*- FTP*- NFS

E-Mail- SMTP

Remote Login- Telnet*- rlogin*

Network Management- SNMP*

Name Management- DNS*

Telnet

Telnet is used for Terminal Emulation.

It allows a user sitting on a remote machine to access the resources of another machine.

It allows you to transfer files from one machine to another.

It also allows access to both directories and files.

It uses TCP for data transfer and hence slow but reliable.

Network File System (NFS)

It is jewel of protocols specializing in file sharing.

It allows two different types of file systems to interoperate.

This is striped down version of FTP.

It has no directory browsing abilities.

It can only send and receive files.

It uses UDP for data transfer and hence faster

but not reliable.

LPD (Line Printer Daemon)

The Line Printer Protocol is designed for Printer sharing.

The LPD along with the LPR (Line Printer Program) allows print jobs to spooled and sent to the networks printers using TCP/IP.

X Window X-windows defines a protocol for the writing of

graphical user interface-based client/Server

application.

Simple Network Management

Protocol SNMP enable a central management of

Network.

Using SNMP an administrator can watch the entire network.

SNMP works with TCP/IP.

IT uses UDP for transportation of the data.

DNS (Domain Name Service)

DNS resolves FQDNs with IP address.

DNS allows you to use a domain name to specify and IP address.

It maintains a database for IP address and Hostnames.

On every query it checks this database and resolves the IP.

Unique addressing allows communication between end stations.

Path choice is based on destination address.

Location is represented by an address

Introduction to TCP/IP

Addresses

172.18.0.2

172.18.0.1

172.17.0.2172.17.0.1

172.16.0.2

172.16.0.1

SA DAHDR DATA10.13.0.0 192.168.1.0

10.13.0.1 192.168.1.1

IPv4 Addressing

32-bit addresses

Commonly expressed in dotted decimal format (e.g., 192.168.10.12)

Each dotted decimal is commonlycalled an octet (8 bits)

IP Addressing

255 255 255 255

DottedDecimal

Maximum

Network Host

32 bits

IP Addressing

255 255 255 255

DottedDecimal

Maximum

Network Host

128

64

32

16 8 4 2 1

11111111 11111111 11111111 11111111Binary

32 bits

1 8 9 16 17 24 25 32

128

64

32

16 8 4 2 1

128

64

32

16 8 4 2 1

128

64

32

16 8 4 2 1

IP Addressing

255 255 255 255

DottedDecimal

Maximum

Network Host

128

64

32

16 8 4 2 1

11111111 11111111 11111111 11111111

10101100 00010000 01111010 11001100

Binary

32 bits

172 16 122 204ExampleDecimal

ExampleBinary

1 8 9 16 17 24 25 32

128

64

32

16 8 4 2 1

128

64

32

16 8 4 2 1

128

64

32

16 8 4 2 1

Class A:

Class B:

Class C:

Class D: Multicast

Class E: Research

IP Address Classes

Network Host Host Host

Network Network Host Host

Network Network Network Host

8 bits 8 bits 8 bits 8 bits

IP AddressingClass A

10.222.135.17

Network # 10

Host # 222.135.17

Range of class A network IDs: 1126

Number of available hosts: 16,777,214

IP AddressingClass B

128.128.141.245

Network # 128.128

Host # 141.245

Range of class B network IDs: 128.1191.254

Number of available hosts: 65,534

IP AddressingClass C

192.150.12.1

Network # 192.150.12

Host # 1

Range of class C network IDs: 192.0.1223.255.254

Number of available hosts: 254

IP Network Address Classes

0000000001111111

10111111

1111111111011111

00000000 00000000

11111111

11111111 00000000 00000000

00000000

# Networks

126

16,384

2,097,152

# Hosts

254

65,534

16,777,214

Class

A

B

C

Class A 35.0.0.0

Class B 128.5.0.0

Class C 132.33.33.0 Network Address Space

Host Address Space

Example

IP Address Classes

1

Class A:

Bits:

0NNNNNNN Host Host Host

8 9 16 17 24 25 32

Range (1-126)

1

Class B:

Bits:

10NNNNNN Network Host Host

8 9 16 17 24 25 32

Range (128-191)

1

Class C:

Bits:

110NNNNN Network Network Host

8 9 16 17 24 25 32

Range (192-223)

1

Class D:

Bits:

1110MMMM Multicast Group Multicast Group Multicast Group

8 9 16 17 2425 32

Range (224-239)

Private Addresses

Class A 10.0.0.0 to 10.255.255.255

Class B 172.16.0.0 to 172.31.255.255

Class C 192.168.0.0 to 192.168.255.255

11111111

Determining Available Host

Addresses

172 16 0 0

10101100 00010000 00000000 00000000

16

15

14

13

12

11

10 9 8 7 6 5 4 3 2 1

Network Host

00000000 00000001

11111111 1111111111111111 11111110

...

...

00000000 00000011

11111101

123

655346553565536-

...

2

65534

N

2N-2 = 216-2 = 65534

Subnet Mask

172 16 0 0

255 255 0 0

255 255 255 0

IP

Address

Default

Subnet

Mask

8-bit

Subnet

Mask

Network Host

Network Host

Network Subnet Host

Also written as /16 where 16 represents the number of 1s in the mask.

Also written as /24 where 24 represents the number of 1s in the mask.

11111111 11111111 00000000 00000000

Decimal Equivalents of Bit

Patterns

1 0 0 0 0 0 0 0 = 128

1 1 0 0 0 0 0 0 = 192

1 1 1 0 0 0 0 0 = 224

1 1 1 1 0 0 0 0 = 240

1 1 1 1 1 0 0 0 = 248

1 1 1 1 1 1 0 0 = 252

1 1 1 1 1 1 1 0 = 254

1 1 1 1 1 1 1 1 = 255

128 64 32 16 8 4 2 1

16

Network Host

172 0 0

10101100

11111111

10101100

00010000

11111111

00010000

00000000

00000000

10100000

00000000

00000000

Subnets not in usethe default

00000010

Subnet Mask without Subnets

172.16.2.160

255.255.0.0

Network

Number

Network number extended by eight bits

Subnet Mask with Subnets

16

Network Host

172.16.2.160

255.255.255.0

172 2 0

10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

00000000

00000000

00000010

Subnet

Network

Number128

192

224

240

248

252

254

255

Subnet Mask with Subnets

(cont.)Network Host

172.16.2.160

255.255.255.192

10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

Subnet

Network number extended by ten bits

16172 2 128

Network

Number128

192

224

240

248

252

254

255

128

192

224

240

248

252

254

255

Addressing Summary Example

16172 2 160

10101100 00010000 1010000000000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

4

1


10101100

11111111

00010000

11111111 11111111

10100000

11000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

16172 2 160


10101100

11111111

00010000

11111111 11111111

10100000

11000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

7

16172 2 160


10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

16172 2 160


10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

5

6

16172 2 160


10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

10000001

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

5

6

16172 2 160


10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

10000001

10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

5

6

7

16172 2 160


10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

10101100 00010000 00000010 10111111

10101100 00010000 00000010 10000001

10101100 00010000 00000010 10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

5

6

7

8

16172 2 160


10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

10101100 00010000 00000010 10111111

10101100 00010000 00000010 10000001

10101100 00010000 00000010 10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

172.16.2.128

172.16.2.191

172.16.2.129

172.16.2.190

1

2

3

4

5

6

7

89

16172 2 160

Variable-Length

Subnet Masks

2001, Cisco Systems, Inc. 3-2003-200

What Is a Variable-Length Subnet Mask?

HQ172.16.0.0/16

HQHQ172.16.0.0/16

What Is a Variable-Length Subnet Mask? (cont.)

172.16.14.32/27

172.16.14. 64/27

172.16.14.96/27

C

B

A

Subnet 172.16.14.0/24 is divided into smaller subnets:

Subnet with one mask at first (/27)

HQHQ172.16.0.0/16


172.16.14.32/27

172.16.14. 64/27

172.16.14.96/27

Subnet 172.16.14.0/24 is divided into smaller subnets:

Subnet with one mask at first (/27)

Then further subnet one of the unused /27 subnets into multiple /30 subnets

C

B

A

HQHQ172.16.0.0/16


Calculating VLSMs

Subnetted Address: 172.16.32.0/20

In Binary 10101100. 00010000.00100000.00000000

Calculating VLSMs (cont.)

VLSM Address: 172.16.32.0/26

In Binary 10101100. 00010000.00100000.00000000


In Binary 10101100. 00010000.00100000.00000000

Network Subnet VLSM

subnet

Host

10101100 . 00010000 .0010 0000.00 000000=172.16.32.0/261st subnet:

VLSM Address: 172.16.32.0/26

In Binary 10101100. 00010000.00100000.00000000


In Binary 10101100. 00010000.00100000.00000000



In Binary 10101100. 00010000.00100000.00000000

VLSM Address: 172.16.32.0/26

In Binary 10101100. 00010000.00100000.00000000

1st subnet: 10101100 . 00010000 .0010 0000.00 000000=172.16.32.0/26

172 . 16 .0010 0000.01 000000=172.16.32.64/26

172 . 16 .0010 0000.10 000000=172.16.32.128/26

172 . 16 .0010 0000. 1 000000=172.16.32.192/26

172 . 16 .0010 0001.00 000000=172.16.33.0/26

Network Subnet VLSM

Subnet

Host

1

2nd subnet:

3rd subnet:

4th subnet:

5th subnet:


A Working VLSM Example

Derived from the 172.16.32.0/20 Subnet


(cont.)

172.16.32.0/26

172.16.32.64/26

172.16.32.128/26

172.16.32.192/26

26 bit mask

(62 hosts)


Derived from the

172.16.33.0/26 Subnet

30 bit mask

(2 hosts)

172.16.32.0/26

172.16.32.64/26

172.16.32.128/26

172.16.32.192/26

26 bit mask

(62 hosts)



(cont.)

172.16.33.0/30

172.16.33.4/30

172.16.33.8/30

172.16.33.12/30

Derived from the

172.16.33.0/26 Subnet

30-Bit Mask

(2 Hosts)

172.16.32.0/26

172.16.32.64/26

172.16.32.128/26

172.16.32.192/26

26-Bit Mask

(62 Hosts)



(cont.)

Route Summarization

2001, Cisco Systems, Inc. 3-213

What Is Route Summarization?

Routing table

172.16.25.0/24

172.16.26.0/24

172.16.27.0/24

172.16.27.0/24

172.16.26.0/24

172.16.25.0/24

A

What Is Route

Summarization? (cont.)

Routing protocols can summarize addresses of several networks into one address

I can route to the 172.16.0.0/16 network.

Routing Table

172.16.0.0/16

B

Routing Table

172.16.25.0/24

172.16.26.0/24

172.16.27.0/24

172.16.27.0/24

172.16.26.0/24

172.16.25.0/24

A

Summarizing Within an Octet

172.16.168.0/24 = 10101100 . 00010000 . 10101 000 . 00000000

Number of Common Bits = 21

Summary: 172.16.168.0/21

Noncommon

Bits = 11

172.16.169.0/24 = 172 . 16 . 10101 001 . 0

172.16.170.0/24 = 172 . 16 . 10101 010 . 0

172.16.171.0/24 = 172 . 16 . 10101 011 . 0

172.16.172.0/24 = 172 . 16 . 10101 100 . 0

172.16.173.0/24 = 172 . 16 . 10101 101 . 0

172.16.174.0/24 = 172 . 16 . 10101 110 . 0

172.16.175.0/24 = 172 . 16 . 10101 111 . 0

Summarizing Addresses in

a VLSM-Designed Network

CorporateNetwork

172.16.0.0/16

172.16.128.0/20

172.16.32.64/26

172.16.32.0/24

172.16.32.128/26

A

B

C

D172.16.64.0/20

Classless

Interdomain Routing

2001, Cisco Systems, Inc. 3-218

Classless Interdomain Routing

Mechanism developed to alleviate exhaustion of addresses and reduce

routing table size

Blocks of Class C addresses assigned to ISPsISPs assign subsets of address space to organizations

Blocks are summarized in routing tables

CIDR Example

ISP

H

B

192.168.8.0/24

192.168.9.0/24

192.168.15.0/24

Networks 192.168.8.0/24 through 192.168.15.0/24 are summarized by the ISP in one advertisement

192.168.8.0/21

A

192.168.8.0/21192.168.9.0/24

WAN Basics

A network that serves users across a broad geographic area

Often uses transmission devices provided by public carriers (Pacific Bell, AT&T, etc.)

This service is commonly referred to as plain old telephone service (POTS)

WANs function at the lower three layers of the OSI reference model

Physical layer, data link layer, and network layer

What Is a WAN?

WAN Overview

Service

Provider

WANs connect sites

Connection requirements vary depending on user requirements and cost

What is a

WAN?

A WAN is a data communications network that covers a relatively broad geographic

area and often uses transmission facilities provided by common carriers, such as

telephone companies. WAN technologies function at the lower three layers of the OSI

reference model: the physical layer, the data link layer, and the network layer.

WAN connection types

Point-to-Point Links or Leased Lines

Circuit Switching

Packet Switching

Point-to-Point Links or

Leased Lines

A point-to-point link is also known as a leased line because its

established path is permanent and fixed for each remote network reached

through the carrier facilities. It uses synchronous serial lines upto 45

Mbps

Leased Line

One connection per physical interface

Bandwidth: 56 kbps1.544 Mbps

Cost effective at 46 hours daily usage

Dedicated connections with predictable throughput

Permanent

Cost varies by distance

Dedicated physical circuit established, maintained, and terminated through a carrier network for each

communication session

Datagram and data stream transmissions

Operates like a normal telephone call

Example: ISDN

WANModem Modem

Circuit Switching

Sets up line like a phone call. No data can transfer before the end-to-end

connection is established.

Uses dial-up modems and ISDN. It is used for low-bandwidth data transfers.

Circuit Switching

POTS Using Modem Dialup

Widely available

Easy to set up

Dial on demand

Asynchronous transmission

Low cost, usage-based

Lower bandwidth access requirements

Telecommuters

Mobile

Users

Modem

Corporate Network

Server

ModemAccess Router

Basic

Telephone

Service

Integrated Services Digital

Network (ISDN)

High bandwidth

Up to 128 Kbps per basic rate interface

Dial on demand

Multiple channels

Fast connection time

Monthly rate plus cost-effective, usage-based billing

Strictly digital

LAN

Server

Company Network

Telecommuter/After-

Hours, Work-at-

Home

BRI

2B+DBRI/PRI

23B+D

30B+D (Europe)

ISDN

Network devices share a point-to-point link to transport packets from a source to a destination across a carrier

network

Statistical multiplexing is used to enable devices to share these circuits

Examples: ATM, Frame Relay, X.25

WANModem Modem

MultiplexingDemultiplexing

Packet Switching

WAN switching method that allows you to sharebandwidth with other companies to save money.

Think of packet switching networks as a party line. As long as you are not constantly transmit-ting data and are instead

using bursty data transfers, packet switching can save you

a lot of money. However, if you have constant data

transfers,then you will need to get a leased line.

Frame Relay and X.25 are packet-switching technologies. Speeds can range from 56Kbps to 2.048Mbps.

Packet Switching

Frame Relay

Permanent, not dialup

Multiple connections per physical interface (permanent virtual circuits)

Efficient handling of bursty (peak performance period) data

Guaranteed bandwidth (typical speeds are 56/64 Kbps, 256 Kbps, and 1.544 Mbps)committed information rate (CIR)

Cost varies greatly by region

Permanent Virtual Circuit (PVC)

X.25

Very robust protocol for low-quality lines

Packet-switched

Bandwidth: 9.6 kbps64 kbps

Well-established technology; large installed base

Worldwide availability

X.25DCE

DTE DTE

DCE

Asynchronous Transfer Mode

(ATM)

Technology capable of transferring voice, video, and data through private and public networks

Uses VLSI technology to segment data, at high speeds, into units called cells

5 bytes of header information

48 bytes of payload

53 bytes total

Cells contain identifiers that specify the data stream to which they belong

Primarily used in enterprise backbones or WAN links

DataHeader

5 48

Cabling the WAN

Core_

Server core_sw_a

ISDN Cloud

Legend

FastEthernet/

Ethernet

ISDN

Dedicated

core_sw_b core_sw_b

ISL

Leased Line/

Frame Relay

WAN Physical Layer

Implementations

Physical layer implementations vary

Cable specifications define speed of linkP

PP

Fra

me

Rela

y

EIA/TIA-232

EIA/TIA-449

X.21 V.24 V.35

HSSI

ISDN BRI (with PPP)

RJ-45

NOTE: Pinouts are

different than RJ-45

used in campus

HD

LC

Differentiating Between WAN

Serial ConnectorsRouter connections

Network connections at the CSU/DSU

EIA/TIA-232 EIA/TIA-449 EIA-530V.35 X.21

CSU/

DSU

End user

device

DTE

DCE

Service

provider

Data Terminal Equipment

End of the users deviceon the WAN link

Data Communications Equipment End of the WAN providers

side of the communication facility

DCE is responsible for clocking

DCEDTE

Modem

CSU/DSU

S S

SS

SS

DTE DTEDCE DCE

Serial Implementation of

DTE versus DCE

WAN Terminating Equipment

Modem

Data Terminal EquipmentDTE

Data Circuit-Terminating Equipment

The Service Providers

Equipment

DCE

EIA/TIA-232

V.35

X.21

HSSITo Corporate

Network

The Customers Equipment

WAN Provider

(Carrier) Network

Physical Cable Types

Usually on the

CustomersPremises

Router

Serial Transmission

WAN Serial connectors use serial transmission Serial transmission uses one bit at time over a

single channel. Parallel transmission can use 8 bits at a time,

but all WANs use serial transmission. Cisco Routers use a proprietary 60 pin serial

connector. Connector at the other end of the cable will

depend on your service provider or end device requirements.

LAN/WAN Devices

1999, Cisco Systems, Inc.www.cisco.com

Hubs

Bridges

Switches

Routers

LAN/WAN Devices

Hub

Device that serves as the center of a star topology network, sometimes

referred to as a multiport repeater,

no forwarding intelligence

Hubs

123

124

125

126

127

128

Hub

Amplifies signals

Propagates signals through the network

Does not filter data packets based on destination

No path determination or switching

Used as network concentration point

Hubs Operate at Physical layer

A B C D

Physical

All devices in the same collision domain

All devices in the same broadcast domain

Devices share the same bandwidth

Hubs: One Collision Domain

More end stations means more collisions

CSMA/CD is used

Bridge

Device that connects and passes packets between two network

segments.

More intelligent than hubanalyzes incoming packets and forwards (or

filters) them based on addressing

information.

Bridge

Segment 1 Segment 2

123

124

125

126

127

128

Corporate Intranet

Hub Hub

More intelligent than a hubcan analyze incoming packets and forward (or filter) them based on addressing information

Collects and passes packets between two network segments

Maintains address tables

Bridge Example

Switches

Use bridging technology to forward traffic between ports.

Provide full dedicated data transmission rate between two stations that are directly connected to the switch ports.

Build and maintain address tables called content-addressable memory (CAM).

10-Mbps

UTP Cable

Dedicated

Workstation

31

Switch

Corporate Intranet

32

3336

100 Mbps 100 Mbps

Uses bridging technology to forward traffic (i.e. maintains address tables, and can filter)

Provides full dedicated transmission rate between stations that are connected to switch ports

Used in both local-area and in wide-area networking

All types availableEthernet, Token Ring, ATM

SwitchingDedicated Media

35

34

Each segment has its own collision domain

All segments are in the same broadcast domain

Data Link

Switches and Bridges Operate

at Data Link Layer

OR1 2 3 1 24

Switches

Each segment has its own collision domain

Broadcasts are forwarded to all segments

Memory

Switch

Routers

Interconnect LANs and WANs

Provide path determination using metrics

Forward packets from one network to another

Control broadcasts to the network

Routing Table

NET INT Metric

124

S0S0E0

100

1.0 4.0

1.3

E0

4.3

S0

2.2

E0

2.1

S0

4.1

4.2

1.1

1.2

Routing Table

NET INT Metric

124

E0S0S0

001

Logical addressing allows for hierarchical network Configuration required Uses configured information to identify paths to networks

Network Layer Functions (cont.)

Routers: Operate at the

Network Layer

Broadcast control

Multicast control

Optimal path determination

Traffic management

Logical addressing

Connects to WAN services

Using Routers to Provide

Remote Access

Internet

Telecommuter

Branch Office

Modem or ISDN TA

Mobile User

Main Office

Network Device Domains

Hub Bridge Switch Router

Collision Domains:

1 4 4 4

Broadcast Domains:

1 1 1 4

Product Selection

Considerations

Provides functionality and features you need today

Capacity and performance

Easy installation and centralized management

Provides network reliability

Investment protection in existing infrastructure

Migration path for change and growth

Seamless access for mobile users and branch offices

Selection Issues:

Scale of the routing features needed

Port density/variety requirements

Capacity and performance

Common user interface

Cisco

700/800

Series

Cisco

1600/1700

Series

Cisco

2500

Series

Cisco

3600

Series

AS

5000

Series

Small Office Solutions

Branch Office Solutions

Central Site Solutions

Cisco

12000 GSR

Series

Cisco

7000

Series

Cisco

10000

Series

Home Office Solutions

Cisco

2600

Series

Cisco Router Products

Visual Objective

Use the product selection tool to

select Cisco Equipment

Router 7200

Router 7300

Router 7500

Router 7600

Router 10000

Router 12000

Fixed and Moduler Interfaces

Some Cisco Routers have fixed interfaces while other are modular.

2500 series routers have set interfaces that cant be changed.

The 2501 Router has two serial connections one 10BaseT AUI interface.

If you need to add a third serial connection you need to buy a new router.

The 1600, 1700, 2600, 3600 and higher routers have modular interfaces.

These Routers allow you to buy what you need and add almost any type of interface you may need later.

Fixed Interfaces

2500 Routerrear view

Serial WAN ports can be fixed

Console


Ethernet AUIEthernet 10BaseT ISDN BRI S/T

Serial WAN ports can be modular


Modular Interfaces

Module

WAN

Interface

Card

Router Internal Components

RAM

It contains the software and data structures that allow the router to function.

The principal software running in RAM is

the Cisco IOS image and the running

configuration. Some routers, such as the

2500 series, run IOS from Flash and not

RAM.

ROM Functions

Contains microcode for basic functions

POST : The microcode used to test the basic functionality of the router hardware and to

determine what components are present.

ROM

ROM

Bootstrap code : the bootstrap code is used to bring the router up during initialization. It contains microcode for basic functions to start and maintain the router. It reads the configuration register to determine how to boot and then, if instructed to do so, loads the IOS software.

ROM monitor : A low-level operating system normally used for manufacturing, testing and troubleshooting.

A partial IOS : This partial IOS can be used to load a new software image into Flash memory and to perform

some other maintainence operations. It does not

support the IP routing and most other routing

functions. Sometimes, this subset of the IOS is

referred to as RXBOOT code.

ROM

Flash memory

Flash memory : is used to contain the IOS software image. Some router run IOS image

directly from Flash and do not need to

transfer it to RAM.

NVRAM

NVRAM : is used mainly to store the configuration. NVRAM uses a battery to

maintain the data when the power is removed

from the router.

Configuration Register

Configuration Register : is used to control how the router boots up.

Configurations can come from many sources.

Configurations will act in device memory.

External Configuration Sources

Basics of Cisco IOS IOS Software delivers Network Services and enables network

services.

Cisco IOS enable the following network services:

Features to carry the chosen network protocols & functions.

Connectivity to provide high-speed traffic between devices.

Security to control access and discourage unauthorized network use.

Scalability to add interfaces and capability as the need for networking grows.

Reliability to ensure dependable access to networked resources.

Cisco IOS software delivers network services and enables networked

applications.

Cisco IOS Software Features

A CLI is used to enter commands.

Operations vary on different internetworking devices.

Users type or paste entries in the console command modes.

Enter key instructs device to parse and execute the command.

Two primary EXEC modes are user mode and privileged mode.

Command modes have distinctive prompts.

Cisco IOS User Interface

Functions

Setting Up A Console

Connection

PCs require an RJ-45-to-DB-9 or RJ-45-to-DB-25 adapter.

COM port settings are 9600 bps, 8 data bits, no parity, 1 stop bit, no flow control.

This provides out-of-band console access.

AUX switch port may be used for a modem-connected console.

Device with Console

Console Connection Console connection is required to configure the router for the

first time.

All Cisco devices are shipped with one Console cable.

It allows you to connect a device and configure, verify and monitor it.

The cable is a rollover cable with RJ-45 connectors

Pinouts for the rollover cable is:

1-8 4-5 7-2

2-7 5-4 8-1

3-6 6-3 ---

Setup terminal emulation program to run at 9600 bps

8 data bits

no parity

1 stop bit

no flow control

Most of the router has an auxiliary port which can connect to a modem This will give you console access to a remote router. The console port and auxiliary port are considered out-of-band

management since you are configuring router out of the network Telnet is considered in-band.

Console Connection

System startup routines initiate router software

Router falls back to startup alternatives if needed

Initial Startup of the Cisco

Router

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.

Router Configuration from

CLI First method of Router configuration is Setup utility

allows a basic initial configuration

Command Line Interface (CLI) can be used for more complex and specific configurations

CLI provides following modes of operation:

User Mode

EXEC Mode

Terminal Configuration / Global Configuration Mode

Terminal configuration Mode gives you access to different configuration Modes.

Unconfigured Versus Configured Router

Bootup Output from the Router

Router#setup

--- System Configuration Dialog ---

Continue with configuration dialog? [yes/no]: yes

At any point you may enter a question mark '?' for help.

Use ctrl-c to abort configuration dialog at any prompt.

Default settings are in square brackets '[]'.

Basic management setup configures only enough connectivity

for management of the system, extended setup will ask you

to configure each interface on the system

Would you like to enter basic management setup? [yes/no]: no

Setup: The Initial

Configuration Dialog

Setup Interface Summary

First, would you like to see the current interface summary? [yes]:

Interface IP-Address OK? Method Status Protocol

BRI0 unassigned YES unset administratively down down

BRI0:1 unassigned YES unset administratively down down

BRI0:2 unassigned YES unset administratively down down

Ethernet0 unassigned YES unset administratively down down

Serial0 unassigned YES unset administratively down down

Interfaces Found During Startup

Setup Initial

Global Parameters

Configuring global parameters:

Enter host name [Router]:wg_ro_c

The enable secret is a password used to protect access to

privileged EXEC and configuration modes. This password, after

entered, becomes encrypted in the configuration.

Enter enable secret: cisco

The enable password is used when you do not specify an

enable secret password, with some older software versions, and

some boot images.

Enter enable password: sanfran

The virtual terminal password is used to protect

access to the router over a network interface.

Enter virtual terminal password: sanjose

Configure SNMP Network Management? [no]:

Setup Initial

Protocol Configurations

Configure LAT? [yes]: no

Configure AppleTalk? [no]:

Configure DECnet? [no]:

Configure IP? [yes]:

Configure IGRP routing? [yes]: no

Configure RIP routing? [no]:

Configure CLNS? [no]:

Configure IPX? [no]:

Configure Vines? [no]:

Configure XNS? [no]:

Configure Apollo? [no]:

Setup Interface

ParametersBRI interface needs isdn switch-type to be configured

Valid switch types are :

[0] none..........Only if you don't want to configure BRI.

[1] basic-1tr6....1TR6 switch type for Germany

[2] basic-5ess....AT&T 5ESS switch type for the US/Canada

[3] basic-dms100..Northern DMS-100 switch type for US/Canada

[4] basic-net3....NET3 switch type for UK and Europe

[5] basic-ni......National ISDN switch type

[6] basic-ts013...TS013 switch type for Australia

[7] ntt...........NTT switch type for Japan

[8] vn3...........VN3 and VN4 switch types for FranceChoose ISDN BRI Switch Type [2]:

Configuring interface parameters:

Do you want to configure BRI0 (BRI d-channel) interface? [no]:

Do you want to configure Ethernet0 interface? [no]: yes

Configure IP on this interface? [no]: yes

IP address for this interface: 10.1.1.33

Subnet mask for this interface [255.0.0.0] : 255.255.255.0

Class A network is 10.0.0.0, 24 subnet bits; mask is /24

Do you want to configure Serial0 interface? [no]:

Setup Script

Review and UseThe following configuration command script was created:

hostname Router

enable secret 5 $1$/CCk$4r7zDwDNeqkxFO.kJxC3G0

enable password sanfran

line vty 0 4

password sanjose

no snmp-server

!

no appletalk routing

no decnet routing

ip routing

no clns routing

no ipx routing

no vines routing

no xns routing

no apollo routing

isdn switch-type basic-5ess

interface BRI0

shutdown

no ip address

!

interface Ethernet0

no shutdown

ip address 10.1.1.31 255.255.255.0

no mop enabled

!

interface Serial0

shutdown

no ip address

end

[0] Go to the IOS command prompt without saving this config.

[1] Return back to the setup without saving this config.

[2] Save this configuration to nvram and exit.

Enter your selection [2]:

Logging In to the Router

There are two main EXEC modes for entering commands.

Cisco IOS Software EXEC

Mode

You can abbreviate a command to the fewest characters that make a unique character string.

Router User-Mode

Command Listwg_ro_c>?

Exec commands:

access-enable Create a temporary Access-List entry

atms

Documents

Ccna Slides