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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.
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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