Design of Ip Configuration of Router

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DESIGN OF IP CONFIGURATION OF ROUTER

The report of the Mini project submitted to JNTUH in partial fulfilment of

requirements for the award of the

Bachelor of Technology

In

Electronics and Communication Engineering

Submitted by

Y.SRAVYA 08L01A0460

Y.SACHIN BABU

08L01A0459

G.TIMOTHY MANOHAR

08L01A0422

Under the guidance of

N. MURALI MOHAN

(Assistant Professor)

Department of Electronics and Communication Engineering

TRR COLLEGE OF ENGINEERING

(Affiliated to JNTUH)

Inole (V), Patancheru(M), Medak (Dist), Andhra Pradesh-502319


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DEPARTMENT OF ELECTRONICS AND COMMUNICATION

ENGINEERING

TRR COLLEGE OF ENGINEERING

(Affiliated to JNTUH)

Inole (V), Patancheru, Medak (dist), Andhra Pradesh.

CERTIFICATE

This is to certify that this report on the mini-project entitled DESIGN OF IP

CONFIGURATION OF ROUTER has been submitted by

Y.SRAVYA 08L01A0460

Y.SACHIN BABU 08L01A0459

G.TIMOTHY MANOHAR 08L01A0423

in partial fulfillment of the requirement for the award ofBachelor of Technology

in Electronics and Communications Engineering. This is a record of the

bonafide work carried out by them from 1st June to 1st July.

Internal Guide Head of the Department

Mr. K. MURALI MOHAN Prof.L.Rangaiah


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Associate Professor

ACKNOWLEDGEMENT

With great pleasure we want to take this opportunity to express our

heartfelt gratitude to all the people who helped us in making this project a grand

success.

We are thankful to Mr.N.Murali Mohan our internal guide, for his

valuable suggestions and guidance given by him during the execution of this

project work.

We are thankful to Mrs.M.Sunitha, our project coordinator, for her

valuable suggestions and guidance given by her during the execution of this

project work.

We are grateful to Prof.L.Rangaiah, Head of the Department of

Electronics and Communication Engineering, for giving us moral support

throughout the period of execution of the project.

We would like to thank ourPrincipalDr.K.Srinivas Rao, for giving us

permission to carry out the project.

We would also like to thank the teaching and non-teaching Staff of

Electronics and Communication Engineering Department for sharing their

knowledge with us.

We express our gratitude to the faculty of ZONTA TECHNOLOGIES,

for permitting us to do this project work with their esteemed thoughts and also for

guiding us through the entire project.

Last but not the least we extend our sincere thanks to our parents and

friends for their moral support throughout the project work. Above all we thankGod Almighty for his manifold mercies in carrying out the project successful.


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ABSTRACT

As we know the importance of IP in our life, even we can say we can

identify the person with statistic IP to that extent.

As part of it, we are going to do mini-project on IP-switch which is a laye-

3 device w.r.to OSI stack and here we are going to perform the following

activities.

We are going to work on CISCO XXXX ROUTER and by end of project;

we should learn/practise the following info.

We are going to configure CISCO XXXX ROUTER step-by-step. This

router is a layer-3 data router which we are going to configure step-by-step. As

part of config, we are going to learn hard-ware, routing protocols like, RIP, OSPF,

BGP, EIGRP and etc... We are going to learn about static/dynamic/de-fault

routing techniques. We are also going to learn VLAN IP ROUTING, INTER

VLAN ROUTING, ACL, NAT and etc. We are also test some of the applications

like, FTP, PING, TRACEROUTE, HTTP, TELNET, DNS and etc


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INDEX

CHAPTERS NAMES PAGES

ABSTRACT i

LIST OF FIGURES iii

LIST OF TABLES iv

ABBREVIATIONS v

1. INTRODUCTION 1

1.1 OSI reference model

1.2 Protocols

1.3 Network elements

1.4 IP address

1.5 Sub netting

1.6 Router

1.7 Routing

2. OPEN SYSTEM INTERCONNECTION 4-8

2.1 History of OSI

2.2 OSI reference model and its layers

3. PROTOCOLS 9-11

4. NETWORK ELEMENTS 12-19

5. IP ADDRESS AND SUBNETTING 20-25

5.1 Internet protocol version 4

5.2 Internet protocol version 6


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5.3 Concept of sub netting

6. ROUTER 26-33

6.1 Types of router

6.2 Significance of MAC address

6.3 Interface and protocols of router

6.4 Memories in router

7. ROUTING 34-54

7.1 Types of routing

7.1.1 Static routing

7.1.2 Dynamic routing

7.1.2.1 RIP

7.1.2.2 OSPF

7.1.2.3 EIGRP

8. CONFIGURATION OF ROUTERS 55-72

8.1 Router commands

8.2 Simulator

8.3 Description of workspace

8.4 Implementing of routing protocol


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LIST OF FIGURES PAGE NO.

Fig 2.1: OSI model 2

Fig 4.1: Repeater 11

Fig 4.2: Hub 13

Fig 4.3: Bridge 13

Fig 4.4: Switch 16

Fig 4.5: Router (wireless) 16

Fig 4.6: wired router 17

Fig 4.7: Gateway (wired) 18

Fig 4.8: Gateway (wireless) 18

Fig 4.9: Network Topology 19

Fig 7.1: Network hierarchy 45

Fig 7.2: AsBRs &ABRs 46

Fig 7.3: Stub area 47

Fig 7.4: NSSA Stub area 48

Fig 8.1: Cisco packet tracer open page 62

Fig 8.2: packet tracer block diagram 72


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LIST OF TABLES page no.

Table 8.1: Router Commands 55-57

Table 8.2: Simulating Item 59-61

Table 8.3: Description of workspace 61-64


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ABBREVIATIONS

OSI Open System Interconnection

IP Internet protocol

LAN Local Area Networking

WAN Wide Area Networking

TCP Transfer Control Protocol

UDP User Diagram Protocol

SDLC Synchronous Data Link Control

HDLC High Level Data Link Control

FDDI Fibre Distributed Data Interface

BRI Basic Rate Interface

PRI Primary Rate Interface

ISDN Integrated Service Digital Network

RIP Routing Information Protocol

OSPF Open Shortest Path First

EIGRP Extended Interior Gateway Routing Protocol

NSSA Not-so-stubby Area

VLSM Variable Length Subnet Mask

AsBRs As Boundary Routers


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DRAM Dynamic Random Access Memory

EPROM Erasable Programmable Read Only Memory

NVRAM Non Volatile Random Access Memory


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CHAPTER 1

INTRODUCTION

This chapter gives a brief introduction of OSI reference model, protocols,

network elements, ip address, sub netting, routers, ACL and password recovery.

1.1.OSI REFERNCE MODEL

The OSI layer shows WHAT needs to be done to send data from an

application on one computer through a network to an application in another

computer but not HOW it should be done. The main idea in OSI is that the process

of communication between two end points in a communication network can be

divided into layers, with each layer adding its own set of special, related functions.

1.2. PROTOCOLS

The OSI model provides a conceptual frame work for communication

between computers, but the model itself is not a method of communication. Actual

communication is made possible by using communication protocols. In context of

data networking a protocol is a set of rules and conventions that governs how

computers exchange information over a network medium. A protocol implements

the functions of one or more of the OSI layers. A wide variety of protocols exist

some of they include:

1.3 .NETWORK ELEMENTS

The basic building blocks those are required in construction and

maintenance of a network is called as the network elements. The various network

elements are:

1. Repeaters


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2. Hubs

3. Switches

4. Bridges

5. Routers

6. Gateway etc

1.4.IP ADDRESS

An internet protocol address (IP ADDRESS) is a numerical label that is

assigned to any device participating in a computer network that uses the internet

protocol for communication between nodes. An IP address serves two principal

functions host or network interfacing identification and location addressing. There

are two types of internet protocol versions that are being widely used IPV4 and

IPV6.

1.5. SUB NETTING

A sub network or subnet, is a logically visible subdivision of an IP Network.

Subnetting is the process of designating some high order bits from the host part

and grouping them with the network mask to form the subnet mask. This divides a

network into smaller subnets. In precise it is a sub network in a network.

1.6. ROUTER

A router is a networking device whose software and hardware are

customized to the tasks of routing and forwarding information. A router has two

or more network interfaces, which may be different types of network (such as

copper cables, fibre or wireless) or different network standards.


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1.7. ROUTING

Routing is the act of moving information across an inter-network from a

source to a destination. Along the way, at least one intermediate node typically is

encountered. Its also referred to as the process of choosing a path over which to

send the packets. Routing is often contrasted with bridging, which might seem to

accomplish precisely the same thing to the casual observer. The primary

difference between the two is that bridging occurs at Layer 2 (the data link layer)

of the OSI reference model, whereas routing occurs at Layer 3 (the network layer).


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CHAPTER 2

OPEN SYSTEM INTERCONNECTION

2.1 HISTORY 0F OSI

The international standard organization introduced the OSI model for

standardization in 1984 in order to provide a reference model to guide product

implementers so that products will consistently work with other products of

different vendors to interoperate in networks. OSI stands for open system

interconnection

The OSI layer shows WHAT needs to be done to send data from an

application on one computer through a network to an application in another

computer but not HOW it should be done. The main idea in OSI is that the process

of communication between two end points in a communication network can be

divided into layers, with each layer adding its own set of special, related functions.

The basic definitions that have to be known before having a detail study

about OSI system are as follows:

SYSTEM:

A system is one or more autonomous computers and their associated

software, peripherals and users, which are capable of information processing

and/or transfer.

SUBSYSTEM:

A logically independent smaller unit of a system. A succession of

subsystems makes up a system.


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LAYER:

A layer is composed of subsystems of the same rank of all the interconnect

systems.

ENTITY:

The functions in a layer are performed by hardware subsystems and/or

software packages. These are known as entities. Entities in the same layer but not

in the same subsystem are known as peer entities. Peer entities communicate using

peer protocols. Data exchange between peer entities is in the form of protocol data

units (PDU). Data exchange between entities of adjacent layers is in the form of

interface data units (IDU). Service data unit (SDU) is a unit of data that has been

passed down from an OSI layer to a lower layer and that has not yet been

encapsulated into a PDU by the lower layer.

2.2 OSI REFERENCE MODEL AND ITS LAYERS:

OSI reference model propose a general layered concept, with provision for

adding or deleting layers as demanded by factors like service complexity,

technology options etc. OSI model is a 7 layered model. These seven layers can be

divided into two categories: upper layers and lower layers.


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The upper layers deal with application issues and generally are implemented

only in software. The lower layers deal with data transport issues. These are

implemented in hardware and software. The seven layers are as described below.

1. Application layer (layer 7)

1. Presentation layer (layer 6)

1. Session layer (layer 5)

1. Transport layer (layer 4)

2. Network layer (layer 3)

3. Data link layer (layer 2)

4. Physical layer (layer 1)

OSI MODEL


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Fig2.1:OSI model

PHYSICAL LAYER:

This layer defines the electrical, mechanical, procedural, and functional

specifications for activating, maintaining, and deactivating the physical link

between communicating network systems. The data is in the form of bits. This

layer specifications define characteristics such as voltage levels, timing of voltage

changes, physical data rates, and physical connectors.


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DATA LINK LAYER:

The data link layer deals with error detections and automatic recovery

procedures required when a message is lost or corrupted. Another important

function performed by data link layer is the data flow control, traffic regulation

mechanism. The data is in the form of frames.

NETWORK LAYER:

The data is in the form of packets. This layer is concerned with

transmission of packets from the source node to destination node. It deals with

routing and switching considerations that are required in establishing a network

connection. It assures a certain quality of service to the upper layers. Since an end

to end connection may involve routing through a number of different networks,

internetworking is an important function of network layer. Addressing schemes,

network capabilities, protocol differences, accounting and billing are all issues to

be handled in internetworking. Network congestion which may occur due to many

messages on a particular route is also tackled by the network layer.

TRANSPORT LAYER:

This layer is first end to end layer in OSI architecture. It provides reliable

data transfer services to the upper layers. It establishes, maintains and terminates

virtual circuits. It makes sure that the data is delivered error free and in the correct

sequence. It also provides acknowledgement of the successful data transmission.

Data is in the form of segments.

SESSION LAYER:


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This layer controls the dialogues (connections) between computers. It

establishes, manages and terminates the connections between local and remote

applications

.

PRESENTATION LAYER:

This layer defines coding and conversion functions. It ensures that

information sent from application layer of one system is readable by the

application layer of another system. Data compression, encryption, translation

functions are supported in this layer. This layer is also sometimes called as syntax

layer.

APPLICATION LAYER:

This layer provides network services directly to applications. This layer is

the closest to the end user, which means that both the OSI application layer and

the user interact directly with the software application. Application layer functions

typically include Identifying communication partners, determining resource

availability, and synchronizing communication.


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CHAPTER 3

PROTOCOLS

The OSI model provides a conceptual frame work for communication

between computers, but the model itself is not a method of communication. Actual

communication is made possible by using communication protocols. In context of

data networking a protocol is a set of rules and conventions that governs how

computers exchange information over a network medium. A protocol implements

the functions of one or more of the OSI layers. A wide variety of protocols exist

some of they include:


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LAN PROTOCOLS:

They operate at physical and data link layers of the OSI model and define

communication over the various LAN media. E.g.: FDDI (fiber distributed data

interface), Ethernet, token ring etc. examples of data link layer protocols are

SDLC (synchronous data link control), HDLC (high level data link control) etc.

WAN PROTOCOLS:

They operate at the lowest three layers of the OSI model and define

communication over the wide area media. SDLC and HDLC are few examples of

these types of protocol

ROUTING PROTOCOLS:

These are network layer protocols that are responsible for exchanging

information between routers so that the routers can select the proper path for

network traffic. E.g.: RIP (router information protocol), OSPF (open shortest path

first) etc.

ROUTED PROTOCOLS:

A routed protocol is a network layer protocol that is used to move traffic

between networks. IP, IPX, and AppleTalk are all examples of these protocols.

TRANSPORT LAYER PROTOCOLS:


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TCP (transfer control protocol), this is a connection oriented protocol it is

reliable. UDP (user datagram protocol) this is a connectionless protocol. It is less

reliable. Etc.

SESSION LAYER PROTOCOLS:

Examples of this layer protocols are NFS (network file system) it allows a

user on a client computer to access files over a network. Zone information

protocols (ZIP) etc.

PRESENTATIONLAYERPROTOCOL:

ASCII (American standard code for information interchange), MPEG

(moving pictures experts group), JPEG ( joint photographic experts group).these

protocols help in data conversion and coding.

APPLICATIONLAYERPROTOCOLS:

FTP (file transfer protocol), SMTP (simple mail transfer protocol), HTTP

(hyper text transfer protocol) etc. All these protocols help in providing services to

the users through various applications.

These are the different protocols present in the various layers of the OSI

reference model

CHAPTER 4


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NETWORK ELEMENTS

The basic building blocks those are required in construction and

maintenance of a network is called as the network elements. The various network

elements are:

1. Repeaters

2. Hubs

3. Switches

4. Bridges

5. Routers

6. Gateway etc

REPEAPTER:

A repeater regenerates a signal from one port to another to which they are

connected. These are operated in physical layer. Hence these devices are also

called as layer one devices.. There are various multiple port repeaters available

e.g.16 port, 8 ports etc. it suppresses noise and helps inefficient transmission of

data. They dont require any addressing information. They are inexpensive and

simple. The disadvantage is that they only support broadcasting and also passes

electrical storms generated by huge amount of computers.


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Fig4.1: repeater

HUBS:

In computer networking, a hub is a small, simple, inexpensive device that

joins multiple computers together. Many network hubs available today support the

Ethernet standard. Other type including USB hub also exist, but Ethernet is the

type traditionally used in home networking. A hub is a layer one device. It does


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not read any of the data passing through them and are not aware of their source or

destination. A hub simply receives the incoming packets and broadcasts these

packets out to all devices on the network. It is generally a rectangular box made of

plastic or fiber that receives power from an ordinary wall outlet. A hub remains

very popular in small networks for its low cost.

Fig4.2 : Hub

BRIDGES:

A bridge is a layer two device. It has only two ports and all its decisions

are made on basis of MAC addresses or layer two addresses but do not depend on

logical addressing. It is used for managing traffic. Basically there are two types of


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bridges. A bridge called as translating bridge connects two different LAN

segments such as token rings, Ethernets etc. and the other type of bridge known as

transparent bridges move data between two similar LAN segments.

fig4.3: Bridge

SWITCHES:

A switch is a layer two device that forwards traffic based on media access

control (MAC) layer i.e. Ethernet or token ring addresses. It is a multiport bridge

and a successor of bridge. It is used to interconnect a number of Ethernet local

area networks to form a large Ethernet network. The purpose of the switch is to

forward the packets only to the desired destination segment of the network

whenever possible minimising the traffic on the network. The disadvantage is that

the switch cannot connect different LAN segments like Ethernets; token rings etc.

There are three distinct features of switch they are:


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ADDRESS LEARNING:

Layer two switches remember the source hardware address of each frame

received on an interface, and they enter this information into a Mac database

called as forward/filter table.

FORWARD FILTER DECISIONS:

When a frame is received on an interface, the switch looks at the

destination hardware address and finds the exit interface in the MAC database.

The frame is only forwarded out the specified destination port.

LOOP AVOIDANCE:

If multiple connections between switches are created for redundancy

purposes network loops can occur. Spanning tree protocol is used to stop network

loops while still permitting redundancy.


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Fig4.4: Switch

ROUTERS:

A router is an electronic device that interconnects two or more computer

networks and selectively interchanges packets of data between them. It is also

called as a layer three switch. They work on the logical addresses known as IP

(internet protocol) addresses. When multiple routers are used in large collection of

interconnected networks, the routers exchange information about target system

addresses, so that each router can build up a table showing the preferred paths

between any two systems on the interconnected networks. The main function of

router is routing and forwarding the data packets.


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Fig4.5:Wireless Router

GATEWAY:

A gateway can translate information between different network data

formats or network architectures. It can translate TCP/IP to AppleTalk so

computers supporting TCP/IP can communicate with Apple brand computers.

Most gateways operate at the application layer, but can operate at the network or

session layer of the OSI model. Gateways will start at the lower level and strip

information until it gets to the required level and repackage the information and

work its way back toward the hardware layer of the OSI model


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Fig 4.6:Router (wired)

Fig4.7:Gateway (wired)


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Fig4.8:Gateway (wireless)

These are the various network elements that are most commonly used in a

network for establishing a efficient connectivity required for effective data

exchange between different devices in different networks.

GENERAL NETWORK TOPOLOGY


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A network topology shows all the network elements that are connected in a

network. It is as shown below:

Fig4.9: Network topology

CHAPTER.5

IP ADDRESSES AND SUBNETTING


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An internet protocol address (IP ADDRESS) is a numerical label that is

assigned to any device participating in a computer network that uses the internet

protocol for communication between nodes. An IP address serves two principal

functions host or network interfacing identification and location addressing. There

are two types of internet protocol versions that are being widely used IPV4 and

IPV6.

5.1 INTERNET PROTOCOL VERSION 4:

It is the fourth revised version in the development of the internet protocol

and it is the first version of the protocol to be widely deployed. IPV4 is

connectionless protocol for use on packet switched link layer network (Ethernet).

It is 32 bit addresses, which limits the address space to 2^32 possible unique

addresses. There are two types of IP addresses private IP addresses and public

addresses.

PUBLIC IP ADDRESSES:

These IPs are allocated to general public and can be used only by the

persons who purchase these IPs. These are unique and are not accessible by

everyone and are publicly registered in the network information system.

PRIVATE IP ADDRESSES:

These IPs are not registered and can be used extensively available for the

public use i.e. anyone can access these IPs. Almost all the LAN IPs are private

IPs.


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CLASSIFICATION OF IP ADDRESSES:

CLASS A:

The range of these IPs is 0.0.0.0 to 127.255.255.255.255. All the IPs in this

range except 10.0.0.0 network are used for private IPs while 10.0.0.0 network is

allocated as public IP. As we know that these are 32 bit addressing the first 8 bits

represent network bits and the remaining 21 bits represent host bits. Class A IPs

are mostly used for large networks.

CLASS B:

The range of this IPs is from 128.0.0.0 to 191.255.255.255.255. All the IPs

in this range except from 172.16.0.0 to 172.32.0.0 are used for private use while

172.16.0.0 172.32.0.0 are used in public IP addressing. The first two octets i.e.

the first 16 address bits represent network bits while the other two octets represent

host bits. This IPs are generally allocated to a medium sized network.

CLASS C:

The range of these IPs is from 192.0.0.0 to 223.255.255.255. all the IPs in

this range are used for private IP addressing except the IPs in the range

192.168.0.0 to 192.168.255.0 which are used for public addressing. The first three

octets represent network bits while the last octet represents host bits. These IPs are

used for small to medium networks.

CLASS D:


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The range of these IPs is from 224.0.0.0 to 239.255.255.255. these IPs are

known as multicast IP addresses .Multicasting is the process of sending packets

from one device to many other devices without any packet duplication.

CLASS E:

The range of these IPs is from 240.0.0.0 to 254.255.255.255. These IPs are

used for experimental purposes only and cannot be assigned for general users.

LIMITATIONS OF IPV4:

ADDRESSING SPACE:

The IPv4 address is 32 bit, which allows to allocate 2^32 address.IPv4

present two level addressing hierarchy i.e. network number and host number. Each

network interface is identified with one or more unique addresses. Two level

addressing hierarchy is convenient but wasteful of the address space.

AUTO CONFIGURATION AND MOBILITY:

New technologies (mobile equipment, wireless network) are emerging and its

use is quickly becoming common. IPV4 did not foresee its use. There is no

automatic way of automatically configure this kind of equipment.

SUPPORT AND REAL TIME APPLICATIONS:


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Services such as the transmission of real time audio and video are becoming

common nowadays. IPV4 does not provide for ways of managing and reserving

bandwidth, which is a drawback to the user of real time services with IPV4.

SECURITY: No security at the network layer.

RAPID GROWTH: Growth of TCP/IP usage into new areas will result in a rapid

growth in the demand for unique IP addresses.

PROLIFERATION: Networks are proliferating rapidly.

5.2 INTERNET PROTOCOL VERSION 6:

IPV6 is an improved version of the current and most widely used internet

protocol, IPV4. Generally the message sent via an IP is broken up into packets,which may travel via a number of different routes to their final destination and are

reassembled into their original form. IPV6 is also known as IPNG (IP Next

Generation). IPV6 includes the following enhancements over IPV4:

1. Expanded address space

2. Improved option mechanism


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3. Address auto configuration

4. Increased addressing flexibility

5. Support for resource allocation

6. Security capabilities

7. It is a hexadecimal addressing system i.e. 128 bit

addressing

In most regards, IPv6 is a conservative extension of IPv4. Most transport and

application-layer protocols need little or no change to operate over IPv6;

exceptions are application protocols that embed internet-layer addresses, such as

FTP etc.IPV6 specifies a new packet format designed to minimize packet header

processing by routers because the headers of IPV4 packets and IPV6 packets are

significantly different, the two protocols are not interoperable.

IPV6 is still in infant stage i.e. not completely used. It takes some time for

the penetration of IPV6 in the market.

5.3 CONCEPT OF SUBNETTING:

A sub network or subnet is a logically visible subdivision of an IP network.

Sub netting is the process of designating some high order bits from the host part


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and grouping them with the network mask to form the subnet mask. This divides a

network into smaller subnets. In precise it is a sub network in a network.

The default subnet mask of class A IP addresses is 255.0.0.0 so it can handle

2^24 host i.e. 16,777,216 hosts. The default subnet mask of class B IP addresses is

255.255.0.0 so it can handle2^16 hosts i.e. 65,536 hosts. The default subnet mask

of class C is 255.255.255.0 so it can handle 2^8 hosts i.e. 256 hosts.

In brief sub netting can be defined as conversion of network bits into host bits.

There are two types of subnet masks fixed length subnet mask and variable length

subnet mask.

FIXED LENGTH SUBNET MASK:

FLSM follows a network wide rule that each network is assigned a fixed

number of subnets irrespective of their requirement and demand. In this type of

sub netting there is a chance of wastage of IP addresses if there are no much hosts

present in the network.

If there is an increased demand for IPs in a network, through FLSM more

subnets other than what they were allocated cannot be provided. For equal

distribution of IPs FLSM is used. To overcome this problem variable length

subnet mask was introduced.

VARIABLE LENGTH SUBNET MASK:

VLSM is a means of allocating IP addressing resources to subnets according

to their individual need rather than some general network-wide rule. This is a

technique used to allow more efficient assignment of IP addresses. To conserve

address space, making it possible to define subnets of varying sizes variable length


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subnet masking was introduced. Through this technique subnets can be provided

as required and there is no wastage or deficit of IPs. For unequal distribution of

IPs VLSM is used.

Number of network bits, number of host bits and the number of masks can be

calculated using the formula: 2^h=required number of hosts.

Thus this topic on IP addresses can be summarised as IP addresses are very

useful in identifying a device on a network and in providing extensive

connectivity and enormous data exchange between remote devices on a network.


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CHAPTER-6

ROUTERS

A router is an electronic device that interconnects two or more computer

networks and selectively interchanges packets of data between them. Each data

packet contains address information that a router can use to determine if the

source and destination are on the same network or if the data packet must be

transferred from one network to another. When multiple routers are used in large

collection of interconnected networks, the routers exchange information about

target system addresses, so that each router can build up a table showing the

preferred paths between any two systems on the interconnected networks and such

table is called as routing table.

A router is a networking device whose software and hardware are

customized to the tasks of routing and forwarding information. A router has two

or more network interfaces, which may be different types of network (such as

copper cables, fiber or wireless) or different network standards. Each network


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interface is a specialised device that converts electric signals from one form to

another.

Routers connect two or more logical subnets each having a different

network addresses. The subnets in the router do not necessarily map one to one to

the physical interfaces of the router. The term layer 3 switching is often used

interchangeably with the term routing. The term switching is generally used to

refer to data forwarding between two network devices with the same network

address. This is also called layer 2 switching or LAN switching.

OPERATION:

Conceptually, a router operates in two operational planes

CONTROL PLANE:

where a router builds a table (routing table) as how a packet

should be forwarded through which interface, by using either statically configured

statements (called static routes) or by exchanging information with other routers in

the network through a dynamical routing protocol.

FORWARDING PLANE:


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where the router actually forwards traffic (called packets) from ingress

(incoming) interfaces to an egress (outgoing) interface that is appropriate for the

destination address that the packet carries with it, by following rules derived from

the routing table that has been built in the control plane.

6.1 TYPES OF ROUTERS:

CUSTOMER EDGE ROUTER:

In short these routers are known as CE routers. These routers are located at

the customer premises that interface to a service provider router i.e. it provides

Ethernet interface between customers LAN and the service provider.

PROVIDER EDGE ROUTER:

In short these routers are known PE routers. These are located at the

service providers network and are connected to CE router directly.

P ROUTER:

A P router is a provider router is a label switch router. These routers have

no knowledge of the customer prefixes; they just label the switch packets. Based

on the way they are connected there are two types of routers. Wired router and

wireless router.

Functions of a router:

1. It performs packet switching i.e. logical addressing


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2. It does packet filtering i.e. access control.

3. It helps in internetwork communication

4. It performs path selection.

6.2 SIGNIFICANCE OF MAC ADDRESS:

MAC stands for Media Access Control. MAC address is a unique

identifier assigned to network interfaces for communications on the physical

network segment. These addresses are often assigned by the manufacturer of the

network interface card and are stored in its hardware, the cards ROM or some

other firmware mechanism. If assigned by the manufacturer, a MAC address

usually encodes the manufacturers registered identification number. It may also

be known as an Ethernet hardware address (EHA) or physical address

6.3 INTERFACES OF A ROUTER:

The interfaces on a router provide network connectivity to the router.

Console and auxiliary ports are used for managing the router. Routers also have

ports for LAN and WAN connectivity.

The LAN interfaces usually include Ethernet, fast Ethernet, fiber

distributed data interface (FDDI) or token ring. The auxiliary port is used to

provide LAN connectivity. One can use a converter to attach LAN to the router.

Synchronous and asynchronous serial interfaces are used for WAN connectivity.

ISDN (Integrated Services Digital Network) interfaces are used to provide ISDN

connectivity. Using ISDN, one can transmit both video and data.


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ETHERNET INTERFACE:

Ethernet is one of the earliest LAN technologies. An Ethernet LAN

typically uses special grades of twisted pair cabling. Ethernet networks can also

use coaxial cable, but this cable medium is becoming less common. The most

commonly installed Ethernet systems are called 10BaseT. The router provides the

interfaces for twisted pair cables.

The Ethernet interfaces on the router are E0, E1, E2, and so on. E stands

for Ethernet, and the number that follows represents the port number. These

interfaces provide connectivity to an Ethernet LAN. In a non-modular Cisco

router, the Ethernet ports are named as above, but in modular routers they are

named as E0/1, where E stands for Ethernet, 0 stands for slot number, and 1 stands

for port number in the slot. Similarly another Ethernet interface called as Fast

Ethernet is available. It is denoted as fa and numbered similar to the Ethernet

interface.

TOKEN RING INTERFACE:

Token Ring is the second most widely used LAN technology after

Ethernet, where all computers are connected in a logical ring topology. Physically,

each host attaches to an MSAU (Multistation Access Unit) in a star configuration.

MSAUs can be chained together to maintain the logical ring topology. An empty

frame called a token is passed around the network. A device on the network can

transmit data only when the empty token reaches the device.

The Token Ring interfaces on a non-modular router are To0, To1, To2 and

so on. To stands for Token Ring and the number following To signifies the

port number. In a modular router, To will be followed by the slot number/port

number.


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FIBER DISTRIBUTED DATA INTERFACE:

Fiber Distributed Data Interface (FDDI) is a LAN technology that uses

fiber optic cable. FDDI is a ring topology that uses four-bit symbols rather than

eight-bit octets in its frames. The 48-bit MAC addresses have 12 four-bit symbols

for FDDI. FDDI is very fast and provides a data transfer rate of 100 Mbps and

uses a token-passing mechanism to prevent collisions.

FDDI uses two rings with their tokens moving in opposite directions to

provide redundancy to the network. Usually only one ring is active at a given

time.

FDDI interfaces on a non-modular Cisco router are F0, F1, F2 and so on.

F stands for FDDI and the number following F signifies the port number. In a

modular router, a slot number/port number will follow F.

INTEGRATED SERVICES DIGITAL NETWORK INTERFACE:

Integrated Services Digital Network (ISDN) is a set of ITU-T

(Telecommunication Standardization Sector of the International

Telecommunications Union) standards for digital transmission over ordinary

telephone copper wire as well as over other media. ISDN provides the integration

of both analog or voice data together with digital data over the same network.

ISDN has two levels of service:


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1. Basic Rate Interface (BRI)

2. Primary Rate Interface (PRI)

The BRI interfaces for ISDN on a non-modular router are BRI0, BRI1, and

so on, with the number following BRI signifying the port number. In a modular

router, BRI is followed by the slot number/port number.

SYNCHRONOUS AND ASYNCHRONOUS INTERFACES:

Synchronous transmission signals occur at the same clock rate and all

clocks are based on a single reference clock. Since asynchronous transmission is a

character-by-character transmission type, each character is delimited by a start and

stop bit, therefore clocks are not needed in this type of transmission. Synchronous

communication requires a response at the end of each exchange of Frames, while

asynchronous communications do not require responses.

Support for the Synchronous Serial interface is supplied on the Multiport

Communications Interface (CSC-MCI) and the Serial Port Communications

Interface (CSC-SCI) network interface cards. The Asynchronous Serial interface

is provided by a number of methods, including RJ-11, RJ-45, and 50-pin Telco

connectors

Some ports can function both as Synchronous Serial interfaces and

Asynchronous Serial interfaces. Such ports are called Async/Sync ports. The

Async/Sync ports support Telco and RJ-11 connectors

TYPES OF PROTOCOLS:


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In general two types of protocols are present they are routed protocols and routing

protocols.

ROUTED PROTOCOLS:

A routed protocol is a network layer protocol that is used to move traffic

between networks. IP, IPX, and AppleTalk are all examples of these protocols.

Routed protocols allow the host on one network to communicate with a host on

another network, with routers forwarding traffic between the source and

destination networks. They are characterized by logical addressing (such as an IP

or IPX address) that only identifies a source or destination host but also the

network (or subnet) on which they reside.

ROUTING PROTOCOLS:

These protocols serve a different purpose. Instead of being used to send

data between source and destination hosts, a routing protocol is used by routers to

exchange routing information with one another. Routing information includes

defining the route, updating the routing table etc. examples of routing protocols is

RIP, EIGRP, OSPF etc

6.4 MEMORIES IN ROUTER:

The various types of memories present in a router are DRAM, EPROM, NVRAM

and FLASH memories.

DRAM:


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DRAM stands for Dynamic Random Access Memory. It has two types of

memories.

Primary, main or processor memory, which is reserved for the CPU to

execute IOS software and to hold the running configuration and routing tables.

Shared, packet or I/O memory which buffers data transmitted or received

by the routers network interfaces.

EPROM:

EPROM stands for Erasable Programmable Read Only Memory is usually

referred to as a boot ROM. EPROM is generally programmed at some point

during the latter stages of manufacture, and cannot generally be changed by the

users. EPROM is generally loaded with two crucial firmware components.

The first is a boot loader which takes over should the device fail to find a

valid bootable image in flash memory, and provides alternate boot options.

NVRAM:

NVRAM stands for Non Volatile Random Access Memory. It stores

important configuration information used by the IOS during boot and by some

programs during start up, which is stored in the starting configuration file.

FLASH MEMORY:


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Flash memory is the most diverse of each of these types and it comes in

many forms, however, its primary use is to store a bootable IOS image from

which a device can start.

Most devices have onboard flash memory from which the device boots,

however some equipment particularly higher end hardware components also have

the capability to boot from an image stored on a flash memory, which ids

removable.

DESIRABLE PROPERTIES OF ROUTERS:

CORRECTNESS AND SIMPLICITY: The packets are to be correctly

delivered. Simpler

Routing algorithm, it is better.

ROBUSTNESS: Ability of the network to deliver packets via some route even in

the face of failures.

STABILITY: The algorithm should converge to equilibrium fast in the face of

changing conditions in the network.

FAIRNESS AND OPTIMALITY: obvious requirements, but conflicting.

EFFICIENCY: Minimum overhead while designing a routing protocol it is

necessary to take into account the following design parameters:

PERFORMANCE CRITERIA:Number of hops, Cost, Delay, Throughput, etc

DECISION TIME: Per packet basis (Datagram) or per session (Virtual-circuit)

basis


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DECISION PLACE: Each node (distributed), Central node (centralized),

Originated node (source)

NETWORK INFORMATION SOURCE: None, Local, Adjacent node, Nodes

along route, All nodes

NETWORK INFORMATION UPDATE TIMING: Continuous, Periodic,

Major load change, Topology change

To summarize the topic about routers, in brief Routers are the layer three

switches belong to the network layer of OSI reference model. They play vital role

in exchange of data packets even between remote devices in a network. Router has

various interfaces that help the user to connect them to various networks.


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CHAPTER-7

ROUTING

Routing is the act of moving information across an inter-network from a

source to a destination. Along the way, at least one intermediate node typically is

encountered. Its also referred to as the process of choosing a path over which to

send the packets. The primary difference between the two is that bridging occurs

at Layer 2 (the data link layer) of the OSI reference model, whereas routing occurs

at Layer 3 (the network layer). The routing algorithm is the part of the network

layer software responsible for deciding which output line an incoming packet

should be transmitted on, i.e. what should be the next intermediate node for thepacket

Routing protocols use metrics to evaluate what path will be the best for a

packet to travel. A metric is a standard of measurement; such as path bandwidth,

reliability, delay, current load on that path etc; that is used by routing algorithms

to determine the optimal path to a destination.

Routing algorithms fill routing tables with a variety of information. Mainly

Destination/Next hop associations tell a router that a particular destination can be


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reached optimally by sending the packet to a particular node representing the

"next hop" on the way to the final destination.

Some of the routing algorithm allows a router to have multiple next hop

for a single destination depending upon best with regard to different metrics. For

example, lets say router R2 is be best next hop for destination D, if path length

is considered as the metric; while Router R3 is the best for the same destination if

delay is considered as the metric for making the routing decision.

8.1 TYPES OF ROUTING:

Depending upon the way the data packets are routed between the routers in

a network and the way in which the routing table is updated, routing is mainly

classified into two types, static routing and dynamic routing.

8.1.1 STATIC ROUTING:

Static routing is the term used to refer to a manual method that is used to

set up routing between networks. The network administrator configures static

routes in a router by entering routes directly into the routing table of a router.

Static routing is a hard coded path in the router that specifies how the router will

get to a certain subnet by using certain path. A static route to everynetwork must

be configured on everyrouter for full connectivity.


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Advantages of Static Routing:

1. Static routes are simple and quick to configure.

1. Static routing is supported on all routing devices and all routers

2. Static routes are easy to predict and understand in small networks.

3. Routers will not share static routes with each other, thus reducing

CPU/RAM overhead and saving bandwidth.

4.

Disadvantages of static routing:

1. Static routes require extensive planning and have high management

overhead. The more routers exist in a network, the more routes that need to

be configured.

2. It is easy to manage in small networks but does not scale well compared to

dynamic routing.

3. Static routing is not fault-tolerant, as any change to the routing

infrastructure (such as a link going down, or a new network added)

requires manual intervention.

4. Routers operating in a purely static environment cannot seamlessly choose

a better Route if a link becomes unavailable.

8.1.2 DYNAMIC ROUTING:


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Dynamic routing is typically used in larger networks to ease the

administrative and operational overhead of using only static routes.

Dynamic routing has evolved to meet the demands of changing network

requirements. It is an adaptive routing that describes the capability of a system,

through which routes are characterized by their destination, to alter the path that

the route takes through the system in response to a change in conditions.

A dynamic routing table is created, maintained, and updated by a routing

protocol running on the router.

Advantages of Dynamic Routing:

1. Scalability and adaptability.

2. Simpler to configure on larger networks.

3. Will dynamically choose a different (or better) route if a link goes down.

4. Ability to load balance between multiple links.

Disadvantages of Dynamic Routing:

1. Routing protocols put additional load on router CPU/RAM.

2. The choice of the best route is in the hands of the routing protocol, and

not the network administrator.


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TYPES OF DYNAMIC ROUTING PROTOCOLS:

There are two types of dynamic routing protocols: Interior gateway routing

protocols and exterior routing protocols.

EXTERIOR ROUTING PROTOCOLS:

To get from place to place outside your network i.e. on the internet you

must use an Exterior Gateway Protocol. Exterior Gateway Protocols handle

routing outside an Autonomous System and get you from your network, through

your Internet provider's network and onto any other network. BGP is used by

companies with more than one Internet provider to allow them to have redundancy

and load balancing of their data transported to and from the internet. used to

connect different router

INTERIOR GATEWAY ROUTING PROTOCOLS:

Interior Gateway Protocols (IGPs) handle routing within an Autonomous

System (one routing domain). In plain English, IGP's figure out how to get from

place to place between the routers you own. The dynamic keep track of paths used

to move data from one end system to another inside a network or set of networks

that you administrate (all of the networks you manage combined are usually just

one Autonomous System). IGP's are how you get all the networks communicating

with each other. These protocols are used to connect the routers of the same

service provider.

Examples of IGRP: Routing Information Protocol (RIP), Extended Interior

Gateway Protocol (EIGRP), Open Shortest Path First (OSPF) etc.


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7.1.2.1 ROUTING INFORMATION PROTOCOL

The Routing Information Protocol (RIP) provides the standard IGP

protocol for local area networks, and provides great network stability,

guaranteeing that if one network connection goes down the network can quickly

adapt to send packets through another connection. In short this protocol is called

as RIP. RIP is Distance vector routing protocol type. Before discussing about RIP

it is important to know certain basic definitions.

METRIC:

Metric is a property of a route in computer networking consisting of any

value used by routing algorithms to determine whether one route should perform

better than another (the route with the lowest metric is the preferred route).

The routing table stores only the best possible routes, while link state or

topological databases may store all other information as well. For example RIP

uses hop count (number of hops) to determine the best possible route. So in simple

language metric is a measure or a unit followed by the routing protocol.

A Metric can include:


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1. Number of hops (hop count)

2. Speed of the path

3. Packet loss (router congestion/conditions)

4. Latency (delay)

5. Path reliability

6. Path bandwidth

7. Cost

8. Load etc.

RIP:

RIP is also called as Routing by rumour .RIP is a dynamic routing protocol

used in local and wide area networks. As we know it is classified as an interior

gateway protocol (IGP). It uses the distance vector routing algorithm. The

protocol has since been extended several times, resulting in RIP Version 2. Both

versions are still in use today, however, they are considered to have been madetechnically obsolete by more advanced techniques such as Open Shortest Path

First (OSPF) etc. RIP has also been adapted for use in IPV6 networks, a standard

known as RIPng (RIP next generation) protocol was also introduced.

HISTORY OF RIP:


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The Routing Information Protocol (RIP) was written by C. Hedrick from

Rutgers University in June 1988, and has since become the most common internet

routing protocol for routing within networks. RIP is based on the computer

program "routed", which was widely distributed with the Unix 4.3 Berkeley

Software Distribution (BSD) operating system, and became the actual standard for

routing in research labs supported by vendors of network gateways.

The earliest RIP protocol was the PUP protocol, which used the Gateway

Information Protocol to exchange routing information, and was invented by a

team that included R. M. Metcalfe, who later developed the Ethernet physical

layer network protocol. The PUP protocol was later upgraded to support the Xerox

Network Systems (XNS) architecture, and named "Routing Information Protocol",

usually just called RIP.

TECHNICAL DETAILS & WORKING:

RIP is a distance-vector routing protocol, which employs the hop count as

a routing metric. The hold down time is 180 seconds. RIP prevents routing loops

by implementing a limit on the number of hops allowed in a path from the source

to a destination. The maximum number of hops allowed for RIP is 15. A hop

count of 16 is considered an infinite distance and used to deprecate inaccessible,

inoperable, or otherwise undesirable routes in the selection process.

What makes RIP work is a routing database that stores information on the

fastest route from computer to computer, an update process that enables each

router to tell other routers which route is the fastest from its point of view, and an

update algorithm that enables each router to update its database with the fastest

route communicated from neighbouring routers:

DATABASE: Each RIP router on a given network keeps a database that stores thefollowing information for every computer in that network.


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IP ADDRESS: The Internet Protocol address of the computer.

Gateway: The best gateway to send a message addressed to that IP address.

DISTANCE: The number of routers between this router and the router that can

send the message directly to that IP address.

ROUTE CHANGE FLAG: A flag that indicates that this information has

changed, used by other routers to update their own databases.

TIMERS: Various timers are also used to help in proper functioning of the

protocol.

ALGORITHM:

The RIP algorithm works like this:

UPDATE: At regular intervals each router sends an update message describing its

routing database to all the other routers that it is directly connected to. Some

routers will send this message as often as every 30 seconds, so that the network

will always have up-to-date information to quickly adapt to changes as computers

and routers come on and off the network.

PROPAGATION: When a router X finds that a router Y has a shorter and faster

path to a router Z, then it will update its own routing database to indicate that fact.


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Any faster path is quickly propagated to neighbouring routers through the update

process, until it is spread across the entire RIP network.

VERSIONS:

There are three versions of the Routing Information Protocol: RIPv1, RIPv2, and

RIPng.

RIP VERSION 1

The original specification of RIP uses class full routing. The periodic

routing updates do not carry subnet information, lacking support for VLSM. This

limitation makes it impossible to have different-sized subnets inside of the same

network class. In other words, all subnets in a network class must have the same

size. There is also no support for router authentication, making RIP vulnerable to

various attacks. The RIP version 1 works when there is only 16 hop counts (0-

15).If there are more than 16 hops between two routers it fails to send data packets

to the destination address.

RIP VERSION 2

Due to the deficiencies of the original RIP specification, RIP version 2

(RIPv2) was developed in 1993 and last standardized in 1998. It included the

ability to carry subnet information, thus supporting Classless Inter-Domain

Routing (CIDR). To maintain backward compatibility, the hop count limit of 15

remained. RIPv2 has facilities to fully interoperate with the earlier specification if

all Must Be Zero protocol fields in the RIPv1 messages are properly specified.
http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routinghttp://en.wikipedia.org/wiki/Classless_Inter-Domain_Routinghttp://en.wikipedia.org/wiki/Classless_Inter-Domain_Routinghttp://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing


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In addition, a compatibility switch feature allows fine-grained

interoperability adjustments.

In an effort to avoid unnecessary load on hosts that do not participate in

routing, RIPv2 multicasts the entire routing table to all adjacent routers at the

address 224.0.0.9, as opposed to RIPv1 which uses broadcast. Unicast addressing

is still allowed for special applications.

RIPng

RIPng (RIP next generation), defined in is an extension of RIPv2 for

support of IPV6 the next generation Internet Protocol. The main differences

between RIPv2 and RIPng are:

1. Support of IPv6 networking.

2. While RIPv2 supports RIPv1 updates authentication, RIPng does not. IPv6

routers were, at the time, supposed to use IPsec for authentication.

3. RIPv2 allows attaching arbitrary tags to routes, RIPng does not;

4. RIPv2 encodes the next-hop into each route entries, RIPng requires

specific encoding of the next hop for a set of route entries

LIMITATIONS OF RIP


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1. Results in network congestions.

2. Time consuming when considered with other types of protocols

3. Convergence is slow

4. Most RIP networks are flat. There is no concept of areas or boundaries in

RIP networks Cannot handle VLSM

These are the various details of routing information protocol.

7.1.2.2OPEN SHORTEST PATH FIRSTOpen Shortest Path First (OSPF) is a routing protocol developed for

Internet Protocol (IP) networks by the Interior Gateway Protocol (IGP) working

group of the Internet Engineering Task Force (IETF). The working group was

formed in 1988 to design an IGP based on the Shortest Path First (SPF) algorithm

for use in the Internet. Similar to the Interior Gateway Routing Protocol (IGRP),

OSPF was created because in the mid-1980s, the Routing Information Protocol

(RIP) was increasingly incapable of serving large, heterogeneous internetworks.

OSPF is a link state routing protocol. OSPF sends link-state

advertisements (LSAs) to all other routers within the same area. OSPF routers use

the SPF (Shortest Path First) algorithm to calculate the shortest path to each node.

SPF algorithm is also known as Dijkstra algorithm.

HISTORY


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OSPF was derived from several research efforts, including Bolt, Beranek,

and Newman's (BBN's) SPF algorithm developed in 1978 for the ARPANET (a

landmark packet-switching network developed in the early 1970s by BBN), Dr.

Radia Perlman's research on fault-tolerant broadcasting of routing information

(1988), BBN's work on area routing (1986).

TECHNICAL DETAILS & WORKING

OSPF is a link-state protocol. We could think of a link as being an

interface on the router. A description of the interface would include, for example,

the IP address of the interface, the mask, the type of network it is connected to, the

routers connected to that network and so on. The collection of all these link-states

would form a link-state database.

LINK-STATE ALGORITHM

OSPF uses a link-state algorithm in order to build and calculate the

shortest path to all known destinations. The algorithm by itself is quite

complicated. The following is a very high level, simplified way of looking at the

various steps of the algorithm:

1) Upon initialization or due to any change in routing information, a router will

generate a link state advertisement. This advertisement will represent the

collection of all link-states on that router.


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2) All routers will exchange link-states by means of flooding. Each router that

receives a link state update should store a copy in its link-state database and then

propagate the update to other routers.

3) After the database of each router is completed, the router will calculate a

Shortest Path Tree to all destinations. The router uses the Dijkstra algorithm to

calculate the shortest path tree. The destinations, the associated cost and the next

hop to reach those destinations will form the IP routing table.

SHORTEST PATH ALGORITHM

The shortest path is calculated using the Dijkstra algorithm. The algorithm

places each router at the root of a tree and calculates the shortest path to each

destination based on the cumulative cost required to reach that destination. Each

router will have its own view of the topology even though all the routers will build

a shortest path tree using the same link-state database.

OSPF COST

The cost (also called metric) of an interface in OSPF is an indication of the

overhead required to send packets across a certain interface. The cost of an

interface is inversely proportional to the bandwidth of that interface. A higher

bandwidth indicates a lower cost. There is more overhead (higher cost) and time

delays involved in crossing a 56k serial line than crossing a 10M Ethernet line.

The formula used to calculate the cost is:

Cost= 10000 0000/bandwidth in bps.


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Shortest Path Tree

Assume we have the following network diagram with the indicated

interface costs. In order to build the shortest path tree for RTA, we would have to

make RTA the root of the tree and calculate the smallest cost for each destination.

The above is the view of the network as seen from RTA. Note the direction of the

arrows in calculating the cost. For example, the cost of RTB's interface to network

128.213.0.0 is not relevant when calculating the cost to 192.213.11.0. RTA can

reach 192.213.11.0 via RTB with a cost of 15 (10+5). RTA can also reach

222.211.10.0 via RTC with a cost of 20 (10+10) or via RTB with a cost of 20

(10+5+5). In case equal cost paths exist to the same destination Cisco's

implementation of OSPF will keep track of up to six next hops to the same

destination.

After the router builds the shortest path tree, it will start building the

routing table accordingly. Directly connected networks will be reached via a

metric (cost) of 0 and other networks will be reached according to the cost

calculated in the tree.

OSPF NETWORKING HIERARCHY

As mentioned earlier, OSPF is a hierarchical routing protocol. It enables

better administration and smaller routing tables due to segmentation of entire

network into smaller areas. OSPF consists of a backbone (Area 0) network that

links all other smaller areas within the hierarchy.


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The following are the important components of an OSPF network:

Fig7.1: Networking Hierarchy

1. Areas

2. Area Border routers

3. Back bone areas

4. AS boundary routers

5. Stub areas


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6. Not-So stubby areas

7. Totally Stubby area

8. Transit Areas

AREAS:

An area consists of routers that have been administratively grouped

together. Usually, an area is a collection of contagious IP subnetted networks.

Routers that are totally within an area are called internal routers. All interfaces on

internal routers are directly connected to networks within the area.

AREA BORDER ROUTER:

An area border router (ABR) is a router that connects one or more areas to the

main backbone network. It is considered a member of all areas it is connected to.

An ABR keeps multiple copies of the link-state database in memory, one for each

area to which that router is connected.

BACKBONE AREA:

An OSPF backbone area consists of all routers in area 0, and all area

border routers (ABRs). The backbone distributes routing information between

different areas.


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Fig 7.2:ASBRs & ABRs

AS BOUNDARY ROUTERS (ASBRS):

Autonomous system boundary routers advertise externally learned routes

throughout the AS. It is a router that is connected to more than one Routing

protocol and that exchanges routing information with routers in other protocols

Stub Areas:

Stub areas are areas that do not propagate AS external advertisements. By

not propagating AS external advertisements, the size of the topological databases

is reduced on the internal routers of a stub area. This in turn reduces the

processing power and the memory requirements of the internal routers.

Not-So-Stubby Areas (NSSA):

An OSPF stub area has no external routes in it. A NSSA allows external

routes to be flooded within the area. These routes are then leaked into other areas.


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This is useful when you have a non-OSPF router connected to an ASBR of a

NSSA. The routes are imported, and flooded throughout the area. However,

external routes from other areas still do not enter the NSSA.

Fig7.3: Stub Area

Fig7.4: NSSA Stub Area

Totally Stubby Area: Only default summary route is allowed in Totally Stubby

Area.

Transit Areas:


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Transit areas are used to pass traffic from an adjacent area to the

backbone. The traffic does not originate in, nor is it destined for, the transit area.

ADVANTAGES OF OSPF:

1. OSPF is an open standard, not related to any particular vendor.

2. OSPF is hierarchical routing protocol, using area 0 (Autonomous System)

at the top of the hierarchy.

3. OSPF uses Link State Algorithm, and an OSPF network diameter can be

much larger than that of RIP.

4. OSPF supports Variable Length Subnet Masks (VLSM), resulting in

efficient use of networking resources.

5. OSPF uses multicasting within areas.

6. After initialization, OSPF only sends updates on routing table sections

which have changed; it does not send the entire routing table, which in turn

conserves network bandwidth.

7. Using areas, OSPF networks can be logically segmented to improve

administration, and decrease the size or the table.

DISADVANTAGES OF OSPF:


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1. OSPF is very processor intensive due to implementation of SPF algorithm.

OSPF maintains multiple copies of routing information, increasing the

amount of memory needed.

2. OSPF is a more complex protocol to implement compared to RIP

As mentioned, OSPF can provide better load-sharing on external links than

other IGPs. These are the various features and functioning of OSPF.

7.1.2.3 EXTENDED INTERIOR GATEWAY ROUTING PROTOCOL

INTRODUCTION:

Extended interior gateway routing protocol in short is called as EIGRP. It

is also called as enhanced interior gateway routing protocol. It is a distance vector

routing protocol with optimizations to minimize both the routing instability

incurred after topology changes, as well as the use of bandwidth and processing

power in the router.

EIGRP is an enhanced version of IGRP. The convergence properties and

the operating efficiency of this protocol have improved significantly.

This allows for an improved architecture while retaining existing

investment in IGRP.EIGRP is a hybrid routing technique. It is a combination of

both distance vector routing and link state routing. It uses band width and delay by

default to calculate its metric.

The convergence technology is based on research conducted at SRI

International. The Diffusing Update Algorithm (DUAL) is the algorithm used to

obtain loop-freedom at every instant throughout a route computation. This allows


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all routers involved in a topology change to synchronize at the same time. Routers

that are not affected by topology changes are not involved in the recomputation.

The convergence time with DUAL rivals that of any other existing routing

protocol.

EIGRP has been extended to be network-layer-protocol independent,

thereby allowing DUAL to support other protocol suites.

WORKING OF EIGRP:

EIGRP has four basic components:

1. Neighbour Discovery/Recovery

2. Reliable Transport Protocol

3. DUAL Finite State Machine

4. Protocol Dependent Modules

Neighbour Discovery/Recovery is the process that routers use to dynamically

learn of other routers on their directly attached networks. Routers must also

discover when their neighbours become unreachable or inoperative. This process

is achieved with low overhead by periodically sending small hello packets. As

long as hello packets are received, a router can determine that a neighbour is alive

and functioning. Once this is determined, the neighbouring routers can exchange

routing information.

The reliable transport is responsible for guaranteed, ordered delivery of

EIGRP packets to all neighbours. It supports intermixed transmission of multicast

or uncast packets. Some EIGRP packets must be transmitted reliably and others


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need not. For efficiency, reliability is provided only when necessary. For example,

on a multi-access network that has multicast capabilities, such as Ethernet, it is not

necessary to send hellos reliably to all neighbours individually.

The DUAL finite state machine embodies the decision process for all route

computations. It tracks all routes advertised by all neighbours. The distance

information, known as a metric, is used by DUAL to select efficient loop free

paths. DUAL selects routes to be inserted into a routing table based on feasible

successors. A successor is a neighbouring router used for packet forwarding that

has a least cost path to a destination that is guaranteed not to be part of a routing

loop.

The protocol-dependent modules are responsible for network layer,

protocol-specific requirements. For example, the IP-EIGRP module is responsible

for sending and receiving EIGRP packets that are encapsulated in IP. IP-EIGRP is

responsible for parsing EIGRP packets and informing DUAL of the new

information received. IP-EIGRP asks DUAL to make routing decisions and the

results of which are stored in the IP routing table. IP-EIGRP is responsible for

redistributing routes learned by other IP routing protocols

EIGRP Concepts:

This section describes some details about EIGRP implementation. Both

data structures and the DUAL concepts are discussed.

NEIGHBOUR TABLE:


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Each router keeps state information about adjacent neighbours. When

newly discovered neighbours are learned,the address and interface of the

neighbour is recorded. This information is stored in the neighbour data structure.

The neighbour table holds these entries. There is one neighbour table for each

protocol dependent module. When a neighbour sends a hello, it advertises a Hold

Time. The Hold Time is the amount of time a router treats a neighbour as

reachable and operational. In other words, if a hello packet isn't heard within the

Hold Time, then the Hold Time expires. When the Hold Time expires, DUAL is

informed of the topology change.

The last sequence number received from the neighbour is recorded so out

of order packets can be detected. A transmission list is used to queue packets for

possible retransmission on a per neighbour basis. Round trip timers are kept in the

neighbour data structure to estimate an optimal retransmission interval.

TOPOLOGY TABLE :

The Topology Table is populated by the protocol dependent modules and

acted upon by the DUAL finite state machine. It contains all destinations

advertised by neighbouring routers. Associated with each entry is the destination

address and a list of neighbours that have advertised the destination. For each

neighbour, the advertised metric is recorded. This is the metric that the neighbour

stores in its routing table. If the neighbour is advertising this destination, it must

be using the route to forward packets. This is an important rule that distance

vector protocols must follow. Also associated with the destination is the metric

that the router uses to reach the destination.


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FEASIBLE SUCCESSORS:

A destination entry is moved from the topology table to the routing table

when there is a feasible successor. All minimum cost paths to the destination form

a set. From this set, the neighbours that have an advertised metric less than the

current routing table metric are considered feasible successors.

Feasible successors are viewed by a router as neighbours that are

downstream with respect to the destination.

These neighbours and the associated metrics are placed in the forwarding

table. When a neighbour changes the metric it has been advertising or a topology

change occurs in the network, the set of feasible successors may have to be re-

evaluated. However, this is not categorized as a route recomputation

.

ROUTE STATES

A topology table entry for a destination can have one of two states. A route

is considered in the Passive state when a router is not performing a route

recomputation. The route is in Active state when a router is undergoing a route

recomputation. If there are always feasible successors, a route never has to go into

Active state and avoids a route recomputation.

When there are no feasible successors, a route goes into Active state and a route

recomputation occurs. A route recomputation commences with a router sending a

query packet to all neighbours. Neighbouring routers can either reply if they have

feasible successors for the destination or optionally return a query indicating that

they are performing a route recomputation. While in Active state, a router cannot


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change the next-hop neighbour it is using to forward packets. Once all replies are

received for a given query, the destination can transition to Passive state and a

new successor can be selected.

ADVANTAGES OF EIGRP:

1. Very low usage of network resources during normal operation; only hello

packets are transmitted on a stable network.

2. When a change occurs, only routing table changes are propagated, not the

entire routing table; this reduces the load the routing protocol itself places

on the network.

3. Rapid convergence times for changes in the network topology (in some

situations convergence can be almost instantaneous)

DISADVANTAGES OF EIGRP:

1. EIGRPs disadvantages are by default automatically summarize routes at

the classful boundaries.

2. Proprietary to CISCO

3. Routers from other vendors cannot use or understand EIGRP


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To summarize in brief EIGRP is a hybrid protocol which employs both the

features of link state and distance vector routing protocols. It is efficient and

overcomes most of the drawbacks of the other routing protocols.

CHAPTER.8

CONFIGURATION OF ROUTERS

8.1 ROUTER COMMANDS

In general there are two types of modes in a router they are privileged

mode and user mode. The following are few commands that help in configuring a

router.


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Enable To get to privileged mode

Config t To get to configuration tab

hostname To assign a name to the router

Interface It interfaces serial/Ethernet ports

No shut Activates interfaces

IP address Assigns IP address

Wr mem To Save the data

Encapsulation ppp Brings all routers on a network to point to


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TABLE 8.1:ROUTER COMMANDS

These are few router commands which are most regularly used. Using

these commands one can configure a router in a network and also can implement

required routing protocol.

In the forthcoming units we shall learn about implementation of routing

protocols especially implementation of Interior gateway routing protocols i.e. RIP,

EIGRP, and OSPF

.

8.2 SIMULATOR

The simulator used to implement the Interior Gateway Routing Protocols

is CISCO PACKET TRACER 5.1. Using this simulator Static routing, RIP,

EIGRP and OSPF are implemented.

Here is a brief introduction about the simulator, which helps to understand

how to use it before working with it.

This simulator allows using different types of routers, switches, connectors

and end devices. We can also develop different network topologies using this

simulator.

CISCO PACKET TRACER 5.1:

PROTOCOL IMPROVEMENTS:

Packet Tracer 5.1 models protocols not included in earlier versions. These

protocols include models of IPv6 Routing, IPv6 and IPv4 Dual Stack, IPv6 ND,


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IPv6 Routing Protocols, DHCPv6, NATv6, Multi-Area OSPF,

Redistribution, RSTP, SSH, Multilayer Switching, and EtherChannel. Also, a

model of the Cisco Catalyst 3560-24PS Multilayer Switch has been added.

EXTENDABLE ARCHITECTURE

GUI IMPROVEMENTS:

Packet Tracer 5.1 retains the logical topology as the primary workspacebut adds additional physical representations of devices, Real-time and Simulation

modes, and a wide variety of views and windows. The GUI supports multiple

languages so the application may be locally translated. New features included in

Packet Tracer 5.1 are the following: Multiuser, ACL Filters, user profile,

improved print functuality, the ability to toggle toolbars in the main interface,

Desktop tab for the Server including IP Configuration and Command Prompt

dialogs, and various Activity Wizard improvements including additional locking

items, the ability to import/export activity instructions, assign point values and

component categories to assessment items, lock the user profile, toggle the

Dynamic Percentage Feedback, and the ability to test an activity without restarting

from beginning.

REPRESENTATION AND VISUALIZATION TOOLS:

An Event List, a form of global network sniffer, is included in Packet

Tracer 5.1. This allows the display of the majority of simulated PDUs as events.

For detailed protocol analysis, these events may be played in a continuous

animation mode, forward, backward or in a stepped through process. Powerful

OSI Layer view and PDU view, and more sophisticated custom PDUs, are also

supported.


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Item Description

Protocol

LAN: Ethernet (including CSMA/CD*), 802.11

wireless*

Switching: VLANs, 802.1q, trunking, VTP, DTP, STP*,

RSTP, multilayer switching, Etherchannel

TCP/IP: HTTP, DHCP, DHCPv6, Telnet, SSH, TFTP,

DNS, TCP*, UDP, IP, IPv6, ICMP, ICMPv6, ARP,

IPv6 ND

Routing: static, default, RIPv1, RIPv2, EIGRP, single-

area OSPF, multi-area OSPF, inter-VLAN routing

Other: ACLs (standard, extended, and named), CDP,

NAT (static, dynamic, and overload), NATv6

WAN: HDLC, PPP, and Frame Relay*

* indicates substantial modeling limitations imposed

Logical Workspace

Network topology creation

Devices: generic, real, and modular

Routers, switches, hosts, hubs, bridges, wireless

access points, wireless routers, clouds, and DSL/cable

modems

Device interconnection through a variety of networking

media

Multiuser remote networks

Physical Workspace

Hierarchy of device, wiring closet, building, city, and

intercity views

Loading of user-created graphics


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Annotation and Authoring Capabilities

Packet Tracer 5.1 improves upon the Activity Wizard of versions 3.2 and

4.0. It also includes templates, or "design patterns," for four different types of

problem-solving activities: concept builders (network modeling problems), skill

builders (pre-lab and post-lab implementation and practice activities), design

problems, and troubleshooting problems.

Packet Tracer 5.1 is a standalone, medium-fidelity, simulation-based

learning environment for networking novices to design, configure, and

troubleshoot computer networks at a CCNA-level of complexity. Packet Tracer

supports student and instructor creation of simulations, visualizations, and

animations of networking phenomena. Like any simulation, Packet Tracer 5.1

relies on a simplified model of networking devices and protocols. Real computer

networks remain the benchmark for understanding network behavior and

developing networking skills.

More details can be available in the help tab of the simulator. The work space

looks as shown below

8.3 DESCRIPTION OF WORK SPACE

When you open Packet Tracer 5.1, by default you will be presented with

the following interface:

This initial interface contains ten components. If you are unsure of what a

particular interface item does, move your mouse over t

Documents

Design of Ip Configuration of Router