TRANING/ PROJECT REPORT

ON NETWORKING

Submitted in partial fulfillment of the requirement for the award of degree of

Bachelors of Technology

In

Computer Science & Engineering (Batch: )

Under the Guidance of:

ACKNOWLEDGEMENT

I owe a great many thanks to a great many people who helped and supported me during the writing of this report .My deepest thanks to Lecturer Mr __________the Guide of the project for guiding and correcting various documents of mine with attention and care. He has taken pain to go through the project and make necessary correction as and when needed. I express my thanks to the director[Mr. _________] of, [Networker Mind], for extending his support.Thanks and appreciation to the helpful people at [____], for their support. I would also thank my Institution and my faculty members without whom this project would have been a distant reality. I also extend my heartfelt thanks to my family and well wishers.

TABLE OF CONTENTS

Sr.No. Content1 What is network?2 What is networking?3 Network Categories4 Network Topology5 Network Types6 OSI model7 Network Cabels8 Network Devices9 A Small School Network10 Software used11 Network addressing12 Routing Protocols13 DHCP14 TFTP15 Tunneling16 Vlan17 Appendix18 Bibliography

What is a Network?

A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.

A computer network connects two or more devices together to share anearly limitless range of information and services, including:• Documents• Email and messaging• Websites• Databases• Music• Printers and faxes• Telephony and videoconferencing

What is networking?

Networks consist of the computers, wiring, and other devices, such as hubs, switches and routers, that make up the network infrastructure. Some devices, such as network interface cards, serve as the computer’s connection to the network. Devices such as switches and routers provide traffic- control strategies for the network. All sorts of different technologies can actually be employed to move data from one place to another, including wires, radio waves, and even microwave technology.Network CategoriesThere are two main types of network categories which are:

Server based Peer-to-peer

Client/Server Networks

 Server based networks, or client/server networks as they are properly called, has a machine at the heart of its operations called the server. A server is a machine that provides services over a network by responding to client requests. Servers rarely have individuals operating it, and even then, it is usually to install, configure or manage its capabilities. The server's essential role on the network is to be continuously available to handle the many requests generated by its clients.

Server-based networks provide centralised control of the entire network environment. The computer systems used for this role are generally more powerful than end-user machines, incorporating faster CPUs, more memory, larger disk drives and other drive types installed, like a tape drive for backup purposes. These are required, because servers are dedicated to handling multiple simultaneous requests from their client communities.

 Server based networks provide centralised verification of user accounts and passwords. Only valid account name and password combinations are allowed access to the network. Client/Server networks typically require a single login to the network itself, meaning that users need to remember long password lists to access various resources. Concentrations of resources on a single server, mean that they are easier to find, as opposed to the peer-to-peer model, were resources were distributed throughout the network since they were attached to multiple machines. The server being a central data repository, means that not only is data more accessible to users, but it also makes life much easier in terms of performing backups, since the data is in a location know to the administrator.

Server-based networks are easier to scale. Peer-to-peer networks bog down seriously as they grow beyond ten users, and serious slow up with 20 users. On the other hand, client/server networks can handle a few users, up to a thousand users as such networks grow to keep pace with an organisations growth and expansion.

Unlike peer-to-peer networks, client/server networks don't come cheap. The server machine itself may cost several thousands of pounds, along with the software to make it run; another thousand pounds. Because of the complex nature of this kind of networking environment, a dedicated administrator is required to be on site at all times to be involved in the day to day running of the network. Hiring an individual of this nature adds considerably to the cost of client/server networks.

Lastly, because the networks operability is so dependant upon the server, this introduces a single point of failure, if the server goes down the network goes down. There are measures available, that can legislate for such failures, however these techniques add even more cost to this solution.

Advantages

Centralised user accounts, security and access controls simplify network administration.

More powerful equipment means more efficient access network resources. Single password login, means access to all resources. Supports greater numbers of users, or networks where resources are heavily

used.

 

Disadvantages More costly to install and maintain. Single point of failure, server goes down, the network goes down. Complex special-purpose software requires appointment of expert staff,

increasing costs. Dedicated hardware and software increases costs.

Peer-to-Peer Networking

This is a simple network configuration that requires some basic know-how to set up. Each of the interconnected machines share dual capability and responsibility on the network. That is to say, that each machine serves a dual purpose or role, i.e. they are both clients and servers to some extent.

The server capability of the machines is very basic. The services provided by each, is no more than the ability to share resources like files, folders, disk drives and printers. They even have the ability to share Internet access.

However, the server functionality of these machines stops there. They cannot grant any of the benefits mentioned previously, since these are functions provided only by a dedicated server operating system.

Because all machines on the network have equal status, hence the term peers, there is no centralised control over shared resources. Sharing is endorsed or repealed by each machine's user. Passwords can be assigned to each individual shared resource whether it is a file, folder, drive or peripheral, again done by the user.

Although this solution is workable on small networks, it introduces the possibility that users may have to know and remember the passwords assigned to every resource, and then re-learn them if the user of a particular machine decides to change them! Due to this flexibility and individual discretion, institutionalised chaos is the norm for peer-to-peer networks.

Security can also be a major concern, because users may give passwords to other unauthorised users, allowing them to access areas of the network that the company does not permit. Furthermore, due to lack of centralisation, it is impossible for users to know and remember what data lives on what machine, and there are no restrictions to prevent them from over-writing the wrong files with older versions of the file.

It may appear that peer-to-peer networks are hardly worthwhile. However, they offer some powerful incentives, particularly for smaller organisations. Networks of this type are the cheapest and easiest to install, requiring only Windows95, a network card for each machine and some cabling. Once connected, users can start to share information immediately and get access to devices.As a result, networks of this type are not scalable and a limit of no more than 10 machines is the general rule.

 

 

Advantages Easy to install and configure. No dedicated server required. Users control their own resources. Inexpensive to purchase and operate. No specialist software required. No dedicated administrator to run the network required.

 

Disadvantages Difficult to employ security. Too many passwords for shared resources. Backups difficult to manage. No centralisation. Limited users.

Three Network Topologies

The network topology describes the method used to do the physical wiring of the network. The main ones are bus,star, and ring.

1. Bus - Both ends of the network must be terminated with a terminator. A barrel connector can be used to extend it.

2. Star - All devices revolve around a central hub, which is what controls the network communications, and can communicate with other hubs. Range limits are about 100 meters from the hub.

3. Ring - Devices are connected from one to another, as in a ring. A data token is used to grant permission for each computer to communicate.

There are also hybrid networks including a star-bus hybrid, star-ring network, and mesh networks with connections between various computers on the network. Mesh networks ideally allow each computer to have a direct connection to each of the other computers. The topology this documentation deals with most is star topology since that is what ethernet networks use.

Basic Network Types

Network types are often defined by function or size. The two most common categories of networks are:• LANs (Local Area Networks)• WANs (Wide Area Networks)

A local area network (LAN) is a group of computers and associated devices that share a common communications line or wireless link. Typically, connected devices share the resources of a single processor or server within a small geographic area (for example, within an office building). Usually, the server has applications and data storage that are shared in common by multiple computer users. A local area network may serve as few as two or three users (for example, in a home network) or as many as thousands of users (for example, in an FDDI network). 

A WAN can be defined one of two ways. The book definition of a WAN is a network that spans large geographical locations, usually to connect multiple LANs. This is a general definition, and not always accurate. A more practical definition of a WAN is a network that traverses a public or commercial carrier, using one of several WAN technologies. A WAN is often under the administrative control of several organizations (or providers), and does not necessarily need to span large geographical distances.

Other networks:-

A MAN (Metropolitan Area Network) is another category of network, though the term is not prevalently used. A MAN is defined as a network that connects LAN’s across a city-wide geographic area.

An internetwork is a general term describing multiple networks connected together. The Internet is the largest and most well-known internetwork. Some networks are categorized by their function, as opposed to their size.

A SAN (Storage Area Network) provides systems with high-speed, lossless access to high-capacity storage devices.

A VPN (Virtual Private Network) allows for information to be securely sent across a public or unsecure network, such as the Internet. Common uses of a VPN are to connect branch offices or remote users to a main office.

What is a Protocol?

A protocol is a set of rules that governs the communications between computers on a network. In order for two computers to talk to each other, they must be speaking the same language. Many different types of network protocols and standards are required to ensure that your computer (no matter which operating system, network card, or application you are using) can communicate with another computer located on the next desk or half-way around the world. The OSI (Open Systems Interconnection) Reference Model defines seven layers of networking protocols.

OSI Reference Model

The Open Systems Interconnection (OSI) model was developed by the International Organization for Standardization (ISO), and formalized in 1984. It provided the first framework governing how information should be sent across a network.

The OSI model consists of seven layers, each corresponding to a specific network function:7 Application6 Presentation5 Session4 Transport3 Network2 Data-link1 Physical

ISO further developed an entire protocol suite based on the OSI model; however, the OSI protocol suite was never widely implemented. The OSI model itself is now somewhat deprecated – modern protocol suites, such as the TCP/IP suite, are difficult to fit cleanly within the OSI model’s seven layers. This is especially true of the upper three layers. The bottom (or lower) four layers are more clearly defined, and terminology from those layers is still prevalently used. Many protocols and devices are described by which lower layer they operate at.

OSI Model - The Upper Layers

The top three layers of the OSI model are often referred to as the upper layers:• Layer-7 - Application layer• Layer-6 - Presentation layer• Layer-5 - Session layer

Protocols that operate at these layers manage application-level functions, and are generally implemented in software. The function of the upper layers of the OSI model can be difficult tovisualize. Upper layer protocols do not always fit perfectly within a layer, and often function across multiple layers.

OSI Model - The Application Layer

The Application layer (Layer-7) provides the interface between the user application and the network. A web browser and an email client are examples of user applications. The user application itself does not reside at the Application layer – the protocol does. The user interacts with the application, which in turn interacts with the application protocol.Examples of Application layer protocols include:• FTP, via an FTP client• HTTP, via a web browser• POP3 and SMTP, via an email client• TelnetThe Application layer provides a variety of functions:• Identifies communication partners• Determines resource availability

• Synchronizes communicationThe Application layer interacts with the Presentation layer below it. As it isthe top-most layer, it does not interact with any layers above it.OSI Model - The Presentation Layer

The Presentation layer (Layer-6) controls the formatting and syntax of user data for the application layer. This ensures that data from the sending application can be understood by the receiving application. Standards have been developed for the formatting of data types, such as text, images, audio, and video. Examples of Presentation layer formats include:• Text - RTF, ASCII, EBCDIC• Images - GIF, JPG, TIF• Audio - MIDI, MP3, WAV• Movies - MPEG, AVI, MOVIf two devices do not support the same format or syntax, the Presentation layer can provide conversion or translation services to facilitate communication.Additionally, the Presentation layer can perform encryption and compression of data, as required. However, these functions can also be performed at lower layers as well. For example, the Network layer can perform encryption, using IPSec.

OSI Model - The Session Layer

The Session layer (Layer-5) is responsible for establishing, maintaining, and ultimately terminating sessions between devices. If a session is broken, this layer can attempt to recover the session.Sessions communication falls under one of three categories:• Full-Duplex – simultaneous two-way communication• Half-Duplex – two-way communication, but not simultaneous• Simplex – one-way communicationMany modern protocol suites, such as TCP/IP, do not implement Session layer protocols. Connection management is often controlled by lower layers, such as the Transport layer.The lack of true Session layer protocols can present challenges for high availability and failover. Reliance on lower-layer protocols for session management offers less flexibility than a strict adherence to the OSI model.

OSI Model - The Lower Layers

The bottom four layers of the OSI model are often referred to as the lower layers:• Layer-4 – Transport layer• Layer-3 – Network layer• Layer-2 – Data-Link layer• Layer-1 – Physical layer

Protocols that operate at these layers control the end-to-end transport of data between devices, and are implemented in both software and hardware.

OSI Model - The Transport Layer

The Transport layer (Layer-4) does not actually send data, despite itsname. Instead, this layer is responsible for the reliable transfer of data, byensuring that data arrives at its destination error-free and in order.Transport layer communication falls under two categories:• Connection-oriented – requires that a connection with specificagreed-upon parameters be established before data is sent.• Connectionless – requires no connection before data is sent.Connection-oriented protocols provide several important services:• Segmentation and sequencing – data is segmented into smallerpieces for transport. Each segment is assigned a sequence number, sothat the receiving device can reassemble the data on arrival.• Connection establishment – connections are established, maintained, and ultimately terminated between devices.• Acknowledgments – receipt of data is confirmed through the use of acknowledgments. Otherwise, data is retransmitted, guaranteeing delivery.• Flow control (or windowing) – data transfer rate is negotiated to prevent congestion.

The TCP/IP protocol suite incorporates two Transport layer protocols:• Transmission Control Protocol (TCP) – connection-oriented• User Datagram Protocol (UDP) – connectionless

OSI Model - The Network Layer

The Network layer (Layer-3) controls internetwork communication, and has two key responsibilities:• Logical addressing – provides a unique address that identifies both the host, and the network that host exists on.• Routing – determines the best path to a particular destination network, and then routes data accordingly.Two of the most common Network layer protocols are:• Internet Protocol (IP)• Novell’s Internetwork Packet Exchange (IPX).IPX is almost entirely deprecated. IP version 4 (IPv4) and IP version 6 (IPv6) are covered in nauseating detail in other guides.

OSI Model - The Data-Link LayerWhile the Network layer is concerned with transporting data between networks, the Data-Link layer (Layer-2) is responsible for transporting data within a network.The Data-Link layer consists of two sublayers:• Logical Link Control (LLC) sublayer

• Media Access Control (MAC) sublayerThe LLC sublayer serves as the intermediary between the physical link and all higher layer protocols. It ensures that protocols like IP can function regardless of what type of physical technology is being used.Additionally, the LLC sublayer can perform flow-control and error checking, though such functions are often provided by Transport layerprotocols, such as TCP.The MAC sublayer controls access to the physical medium, serving as mediator if multiple devices are competing for the same physical link. Datalink layer technologies have various methods of accomplishing this -Ethernet uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD), and Token Ring utilizes a token. Ethernet is covered in great detail in another guide.The Data-link layer packages the higher-layer data into frames, so that the data can be put onto the physical wire. This packaging process is referred to as framing or encapsulation.The encapsulation type will vary depending on the underlying technology.Common Data-link layer technologies include following:• Ethernet – the most common LAN data-link technology• Token Ring – almost entirely deprecated• FDDI (Fiber Distributed Data Interface)• 802.11 Wireless• Frame-Relay• ATM (Asynchronous Transfer Mode)The data-link frame contains the source and destination hardware (or physical) address. Hardware addresses uniquely identify a host within a network, and are often hardcoded onto physical network interfaces.However, hardware addresses contain no mechanism for differentiating one network from another, and can only identify a host within a network.The most common hardware address is the Ethernet MAC address.

OSI Model - The Physical Layer

The Physical layer (Layer-1) controls the signaling and transferring of raw bits onto the physical medium. The Physical layer is closely related to the Data-link layer, as many technologies (such as Ethernet) contain both datalink and physical functions.The Physical layer provides specifications for a variety of hardware:• Cabling• Connectors and transceivers• Network interface cards (NICs)• Wireless radios• Hubs

Network Cables

Primary Cable Types

The vast majority of networks today are connected by some sort of wiring or cabling that acts as a network transmission medium that carries signals between computers. Many cable types are available to meet the varying needs and sizes of networks, from small to large.

Cable types can be confusing. Belden, a leading cable manufacturer, publishes a catalog that lists more than 2200 types of cabling. Fortunately, only three major groups of cabling connect the majority of networks:

Coaxial cable Twisted-pair (unshielded and shielded) cable Fiber-optic cable

The next part of this lesson describes the features and components of these three major cable types. Understanding their differences will help you determine which type of cabling is appropriate in a given context. 

Coaxial CableAt one time, coaxial cable was the most widely used network cabling. There were a couple of reasons for coaxial cable's wide usage: it was relatively inexpensive, and it was light, flexible, and easy to work with.

In its simplest form, coaxial cable consists of a core of copper wire surrounded by insulation, a braided metal shielding, and an outer cover. Figure 2.1 shows the various components that make up a coaxial cable.

The term shielding refers to the woven or stranded metal mesh (or other material) that surrounds some types of cabling. Shielding protects transmitted data by absorbing stray electronic signals, called noise, so that they do not get onto the cable and distort the data. Cable that contains one layer of foil insulation and one layer of braided metal shielding is referred to as dual shielded. For environments that are subject to higher interference, quad shielding is available. Quad shielding consists of two layers of foil insulation and two layers of braided metal shielding.

Figure 2.1 Coaxial cable showing various layers

The core of a coaxial cable carries the electronic signals that make up the data. This wire core can be either solid or stranded. If the core is solid, it is usually copper.

Surrounding the core is a dielectric insulating layer that separates it from the wire mesh. The braided wire mesh acts as a ground and protects the core from electrical noise and crosstalk. (Crosstalk is signal overflow from an adjacent wire. For a more detailed discussion of crosstalk, see the section Unshielded Twisted-Pair (UTP) Cable, later in this lesson.)

The conducting core and the wire mesh must always be kept separate from each other. If they touch, the cable will experience a short, and noise or stray signals on the mesh will flow onto the copper wire. An electrical short occurs when any two conducting wires or a conducting wire and a ground come into contact with each other. This contact causes a direct flow of current (or data) in an unintended path. In the case of household electrical wiring, a short will cause sparking and the blowing of a fuse or circuit breaker. With electronic devices that use low voltages, the result is not as dramatic and is often undetectable. These low-voltage shorts generally cause the failure of a device; and the short, in turn, destroys the data.

A nonconducting outer shield—usually made of rubber, Teflon, or plastic—surrounds the entire cable.

Coaxial cable is more resistant to interference and attenuation than twisted-pair cabling. As shown in attenuation is the loss of signal strength that begins to occur as the signal travels farther along a copper cable.

Attenuation causes signals to deteriorate

The stranded, protective sleeve absorbs stray electronic signals so that they do not affect data being sent over the inner copper cable. For this reason, coaxial cabling is a good choice for longer distances and for reliably supporting higher data rates with less sophisticated equipment.

Types of Coaxial Cable

There are two types of coaxial cable:

Thin (thinnet) cable Thick (thicknet) cable

Which type of coaxial cable you select depends on the needs of your particular network.

Thinnet Cable Thinnet cable is a flexible coaxial cable about 0.64 centimeters (0.25 inches) thick. Because this type of coaxial cable is flexible and easy to work with, it can be used in almost any type of network installation. Figure shows thinnet cable connected directly to a computer's network interface card (NIC).

Close-up view of thinnet cable showing where it connects to a computer

Thinnet coaxial cable can carry a signal for a distance of up to approximately 185 meters (about 607 feet) before the signal starts to suffer from attenuation.

Cable manufacturers have agreed upon specific designations for different types of cable. (Table 2.1 lists cable types and descriptions.) Thinnet is included in a group referred to as the RG-58 family and has 50ohm impedance. (Impedance is the resistance, measured in ohms, to the alternating current that flows in a wire.) The principal distinguishing feature of the RG-58 family is the center core of copper. shows two examples of RG-58 cable, one with a stranded wire core and one with a solid copper core.

RG-58 coaxial cable showing stranded wire and solid copper cores

Thicknet Cable Thicknet cable is a relatively rigid coaxial cable about 1.27 centimeters (0.5 inches) in diameter. Figure shows the difference between thinnet and thicknet cable. Thicknet cable is sometimes referred to as Standard Ethernet because it was the first type of cable used with the popular network architecture Ethernet. Thicknet cable's copper core is thicker than a thinnet cable core.

Thicknet cable has a thicker core than thinnet cable

The thicker the copper core, the farther the cable can carry signals. This means that thicknet can carry signals farther than thinnet cable. Thicknet cable can carry a signal for 500 meters (about 1640 feet). Therefore, because of thicknet's ability to support data transfer over longer distances, it is sometimes used as a backbone to connect several smaller thinnet-based networks.

Figure shows a device called a transceiver. A transceiver connects the thinnet coaxial cable to the larger thicknet coaxial cable. A transceiver designed for thicknet Ethernet includes a connector known as a vampire tap, or a piercing tap, to make the actual physical connection to the thicknet core. This connector is pierced through the insulating layer and makes direct contact with the conducting core. Connection from the transceiver to the NIC is made using a transceiver cable (drop cable) to connect to the attachment unit interface (AUI) port connector on the card. An AUI port connector for thicknet is also known as a Digital Intel Xerox (DIX)connector (named for the three companies that developed it and its related standards) or as a DB-15 connector.

Thicknet cable transceiver with detail of a vampire tap piercing the core

Thinnet vs. Thicknet Cable As a general rule, the thicker the cable, the more difficult it is to work with. Thin cable is flexible, easy to install, and relatively inexpensive. Thick cable does not bend easily and is, therefore, harder to install. This is a consideration when an installation calls for pulling cable through tight spaces such as conduits and troughs. Thick cable is more expensive than thin cable, but will carry a signal farther.

Coaxial-Cable Grades and Fire Codes

The type of cable grade that you should use depends on where the cables will be laid in your office. Coaxial cables come in two grades:

Polyvinyl chloride (PVC) grade Plenum grade

Polyvinyl chloride (PVC) is a type of plastic used to construct the insulation and cable jacket for most types of coaxial cable. PVC coaxial cable is flexible and can be easily routed through the exposed areas of an office. However, when it burns, it gives off poisonous gases.

A plenum is the shallow space in many buildings between the false ceiling and the floor above; it is used to circulate warm and cold air through the building. Figure 2.11 shows a typical office and where to use—or not use—PVC and plenum-grade cables. Fire codes give very specific instructions about the type of wiring that can be routed through this area, because any smoke or gas in the plenum will eventually blend with the air breathed by everyone in the building.

 

Plenum-grade cabling contains special materials in its insulation and cable jacket. These materials are certified to be fire resistant and produce a minimum amount of smoke; this reduces poisonous chemical fumes. Plenum cable can be used in the plenum area and in vertical runs (for example, in a wall) without conduit. However, plenum cabling is more expensive and less flexible than PVC cable.

You should consult your local fire and electrical codes for specific regulations and requirements for running networking cable in your office.Coaxial-Cabling Considerations

Consider the following coaxial capabilities when making a decision about which type of cabling to use.

Use coaxial cable if you need a medium that can:

Transmit voice, video, and data. Transmit data for greater distances than is possible with less expensive cabling. Offer a familiar technology with reasonable data security.

Twisted-Pair Cable

In its simplest form, twisted-pair cable consists of two insulated strands of copper wire twisted around each other. Figure 2.12 shows the two types of twisted-pair cable: unshielded twisted-pair (UTP) and shielded twisted-pair (STP) cable.

Figure 2.12 Unshielded twisted-pair and shielded twisted-pair cables

A number of twisted-pair wires are often grouped together and enclosed in a protective sheath to form a cable. The total number of pairs in a cable varies. The twisting cancels out electrical noise from adjacent pairs and from other sources such as motors, relays, and transformers.

Unshielded Twisted-Pair (UTP) Cable

UTP, using the 10BaseT specification, is the most popular type of twisted-pair cable and is fast becoming the most popular LAN cabling. The maximum cable length segment is 100 meters, about 328 feet.

Traditional UTP cable, as shown in Figure consists of two insulated copper wires. UTP specifications govern how many twists are permitted per foot of cable; the number of twists allowed depends on the purpose to which the cable will be put. In North America, UTP cable is the most commonly used cable for existing telephone systems and is already installed in many office buildings.

The 568A Commercial Building Wiring Standard of the Electronic Industries Association and the Telecommunications Industries Association (EIA/TIA) specifies the type of UTP cable that is to be used in a variety of building and wiring situations. The objective is to ensure consistency of products for customers. These standards include five categories of UTP:

Category 1 This refers to traditional UTP telephone cable that can carry voice but not data transmissions. Most telephone cable prior to 1983 was Category 1 cable.

Category 2 This category certifies UTP cable for data transmissions up to 4 megabits per second (Mbps). It consists of four twisted pairs of copper wire.

Category 3 This category certifies UTP cable for data transmissions up to 16 Mbps. It consists of four twisted pairs of copper wire with three twists per foot.

Category 4 This category certifies UTP cable for data transmissions up to 20 Mbps. It consists of four twisted pairs of copper wire.

Category 5 This category certifies UTP cable for data transmissions up to 100 Mbps. It consists of four twisted pairs of copper wire.

Most telephone systems use a type of UTP. In fact, one reason why UTP is so popular is because many buildings are prewired for twisted-pair telephone systems. As part of the prewiring process, extra UTP is often installed to meet future cabling needs. If preinstalled twisted-pair cable is of sufficient grade to support data transmission, it can be used in a computer network. Caution is required, however, because common telephone wire might not have the twisting and other electrical characteristics required for clean, secure, computer data transmission.

One potential problem with all types of cabling is crosstalk. Figure shows crosstalk between two UTP cables. (As discussed earlier in this lesson, crosstalk is defined as signals from one line interfering with signals from another line.) UTP is particularly susceptible to crosstalk, but the greater the number of twists per foot of cable, the more effective the protection against crosstalk.

Crosstalk occurs when signals from one line bleed into another line

Shielded Twisted-Pair (STP) Cable

STP cable uses a woven copper-braid jacket that is more protective and of a higher quality than the jacket used by UTP. Figure shows a two-twisted-pair STP cable. STP also uses a foil wrap around each of the wire pairs. This gives STP excellent shielding to protect the transmitted data from outside interference, which in turn allows it to support higher transmission rates over longer distances than UTP.

STP cable

Use twisted-pair cable if:

Your LAN is under budget constraints. You want a relatively easy installation in which computer connections are simple.

Do not use twisted-pair cable if: Your LAN requires a high level of security and you must be absolutely sure of data

integrity. You must transmit data over long distances at high speeds.

Fiber-Optic Cable

In fiber-optic cable, optical fibers carry digital data signals in the form of modulated pulses of light. This is a relatively safe way to send data because, unlike copper-based cables that carry data in the form of electronic signals, no electrical impulses are carried over the fiber-optic cable. This means that fiberoptic cable cannot be tapped, and its data cannot be stolen.Fiber-optic cable is good for very high-speed, high-capacity data transmission because of the purity of the signal and lack of signal attenuation.

Fiber-Optic Cable Composition

An optical fiber consists of an extremely thin cylinder of glass, called the core, surrounded by a concentric layer of glass, known as the cladding. The fibers are sometimes made of plastic. Plastic is easier to install, but cannot carry the light pulses for as long a distance as glass. Because each glass strand passes signals in only one direction, a cable includes two strands in separate jackets. One strand transmits and one receives. A reinforcing layer of plastic surrounds each glass strand, and Kevlar fibers provide strength. See Figure for an illustration of fiber-optic

cable. The Kevlar fibers in the fiber-optic connector are placed between the two cables. Just as their counterparts (twisted-pair and coaxial) are, fiber-optic cables are encased in a plastic coating for protection.

Fiber-optic cable

Fiber-optic cable transmissions are not subject to electrical interference and are extremely fast, currently transmitting about 100 Mbps with demonstrated rates of up to 1 gigabit per second (Gbps). They can carry a signal—the light pulse—for many miles.

Fiber-Optic Cabling Considerations

Use fiber-optic cable if you:

Need to transmit data at very high speeds over long distances in very secure media.

Do not use fiber-optic cable if you: Are under a tight budget. Do not have the expertise available to properly install it and connect devices to it.

Network devices

A Network card (also called a Network Adapter or Network Interface Card, or NIC for short) acts as the interface between a computer and a network cable. The purpose of the network card is to prepare, send, and control data on the network.

A network card usually has two indicator lights (LEDs):

The green LED shows that the card is receiving electricity; The orange (10 Mb/s) or red (100 Mb/s) LED indicates network activity (sending or

receiving data).To prepare data to be sent the network card uses a transceiver, which transforms parallel data into serial data. Each cart has a unique address, called a MAC address, assigned by the card's manufacturer, which lets it be uniquely identified among all the network cards in the world.Network cards have settings which can be configured. Among them are hardware interrupts (IRQ), the I/O address and the memory address (DMA).To ensure that the computer and network are compatible, the card must be suitable for the computer's data bus architecture, and have the appropriate type of socket for the cable. Each card is designed to work with a certain kind of cable. Some cards include multiple interface connectors (which can be configured using jumpers, DIP switches, or software). The most commonly used are RJ-45 connectors. 

Note: Certain proprietary network topologies which use twisted pair cables employ RJ-11 connectors. These topologies are sometimes called "pre-10BaseT ".Finally, to ensure that the computer and network are compatible, the card must by compatible with the computer's internal structure (data bus architecture) and have a connector suitable for the kind of cabling used.

Hubs

A special type of network device called the hub can be found in many home and small business networks. Though they've existed for many years, the popularity of hubs has exploded recently, especially among people relatively new to networking.

A hub is a small rectangular box, often made of plastic, that receives its power from an ordinary wall outlet. A hub joins multiple computers (or other network devices) together to form a single network segment. On this network segment, all computers can communicate directly with each other. Ethernet hubs are by far the most common type, but hubs for other types of networks such as USB also exist.A hub includes a series of ports that each accept a network cable. Small hubs network four computers. They contain four or sometimes five ports, the fifth port being reserved for "uplink" connections to another hub or similar device. Larger hubs contain eight, 12, 16, and even 24 ports.Key Features of HubsHubs classify as Layer 1 devices in the OSI model. At the physical layer, hubs can support little in the way of sophisticated networking. Hubs do not read any of the data passing through them and are not aware of their source or destination. Essentially, a hub simply receives incoming packets, possibly amplifies the electrical signal, and broadcasts these packets out to all devices on the network - including the one that originally sent the packet!

Technically speaking, three different types of hubs exist:

passive active intelligent

Passive hubs do not amplify the electrical signal of incoming packets before broadcasting them out to the network. Active hubs, on the other hand, do perform this amplification, as does a different type of dedicated network device called a repeater. Some people use the terms concentrator when referring to a passive hub and multiport repeater when referring to an active hub.Intelligent hubs add extra features to an active hub that are of particular importance to businesses. An intelligent hub typically is stackable (built in such a way that multiple units can be placed one on top of the other to conserve space). It also typically includes remote management capabilities via SNMPand virtual LAN (VLAN) support.Hubs remain a very popular device for small networks because of their low cost.A network switch is a small hardware device that joins multiple computers together within one local area network (LAN). Technically, network switches operate at layer two (Data Link Layer) of the OSI model.

Switches

Network switches appear nearly identical to network hubs, but a switch generally contains more intelligence (and a slightly higher price tag) than a hub. Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately. By delivering messages only to the connected device intended, a network switch conserves network bandwidth and offers generally better performance than a hub.

As with hubs, Ethernet implementations of network switches are the most common. Mainstream Ethernet network switches support either 10/100Mbps Fast Ethernet or Gigabit Ethernet(10/100/1000) standards.

Different models of network switches support differing numbers of connected devices. Most consumer-grade network switches provide either four or eight connections for Ethernet devices. Switches can be connected to each other, a so-called daisy chaining method to add progressively larger number of devices to a LAN.

HUB vs SWITCH

hub:- It is a multiple-port repeater. any signals send via the hub is transmitted to all the the ports on the hubswitch:- It transmit data only to the destination port.hub: Each port of hub is collision domain&broadcast domainswitch: Each port of switch is collision domain & each vlan is broadcast domainhub: is layer 1 device which do not breaks collision domain.ie if more devices are added the bandwith will be shared.switch is layer 2 device which breaks collision domain.ie every device connected to the switch has the equal bandwidth.

Router

A router is specialized computer connected to more than one network running software that allows the router to move data from one networkto another. Routers operate at the network layer (OSI Model's layer 3). The primary function of a router is to connect networks together and keep certain kinds of broadcast traffic under control. There are several companies that make routers:Cisco (Linksys), Juniper, Nortel (Bay Networks),Redback, Lucent, 3Com, and HP just to name a few.

Routers used in networks perform the following functions:

1. Restrict broadcasts to the LAN2. Act as the default gateway.3. Move (route) data between networks4. Learn and advertise loop free paths

RESTRICT BROADCASTS TO THE LANNetworks (especially Ethernet networks use broadcast communication at

the physical,datalink and network layer. Network layer broadcasts are transmissions sent to all

hosts using the network layer protocol (usually Internet Protocol [IP] or IPX). Network broadcastcommunication is used to communicate certain kinds of information that makes the networkfunction (ARP, RARP, DHCP, IPX-SAP broadcasts etc.). Since several devices could attempt to transmit simultaneously and cause collisions, it is preferable to separate large sets of hosts into different broadcast domains using a switch, or router.

As the number of hosts on the network increases, the amount of broadcast traffic increases. If enough broadcast traffic is present on the network, then ordinary communication across the network becomes difficult.To reduce broadcasts, a network administrator can break up a network with a large number of hosts into two smaller networks. Broadcasts are then restricted to each network, and the router performs as the 'default gateway' to reach the hosts on the other networks.ACT AS THE DEFAULT GATEWAYEspecially in today's networks, people are connecting to the Internet. When your computerwants to talk to a computer on another network, it does so by sending your data to thedefault gateway (your local router). The router receives your data, looks for the remote address of that far-off computer makes a routing decision and forwards your data out a different interface that is closer to that remote computer. There could be several routers between you and the remote computer, so several routers will take part in handing off thepacket, much like a fireman's bucket brigade.MOVE (ROUTE) DATA BETWEEN NETWORKSRouters have the capability to move data from one network to another.

networks managed by different organizations to exchange data. They create a networkbetween them and exchange data between the routers on that network. Because a router can accept traffic from any kind of network it is attached to, and forward it to any other network, it can also allow networks that could not normally communicate with each other to exchange data. In technical terms, a token ring network and an ethernet network can communicate over a serial network. Routers make all this possible.A router can take in an Ethernet frame, strip the ethernet data off, and then drop the IP data into a frame of another type such as SDH/SONET, PDH/T1, ATM, FDDI. In this way a router can also perform 'protocol conversion', provided it has the appropriate hardware and software to support such a function. The whole point, however, is to forward the data from the interface it receives data on, to another interface that retransmits the received data onto another interface serving another network.LEARN AND ADVERTISE LOOP-FREE PATHSRouters can only learn and advertise routes dynamically if they are using a routing protocol such as RIP, OSPF, EIGRP, IS-IS or BGP.   Otherwise, a human has to configure the routes by hand, which is called static routing.

Routing moves data on a hop-by-hop basis, what is often called 'hot potato' routing.  If a set of routers ends up passing the data around in a circle, without reaching the destination, it's called a 'routing loop'.  Packets get tossed around the loop until they die of old age:  their 'Time To Live' counter in the IP datagram is decremented as it passes through each router and eventually it reaches zero and is discarded.

A small school network

Software Used:-1.-Cisco packet tracerCisco Packet Tracer is a powerful network simulation program that allows students to experiment with network behavior and ask “what if” questions. As an integral part of the Networking Academy comprehensive learning experience, Packet Tracer provides simulation, visualization, authoring, assessment, and collaboration capabilities and facilitates the teaching and learning of complex technology concepts.Packet Tracer supplements physical equipment in the classroom by allowing students to create a network with an almost unlimited number of devices, encouraging practice, discovery, and troubleshooting. The simulation-based learning environment helps students develop 21st century skills such as decision making, creative and critical thinking, and problem solving. Packet Tracer complements the Networking Academy curricula, allowing instructors to easily teach and demonstrate complex technical concepts and networking systems design.

2.GNS(graphical network simulator)

GNS is a graphical network simulator that allows simulation of complex networks.

To provide complete and accurate simulations, GNS3 is strongly linked with:

Dynamips, a Cisco IOS emulator. Dynagen, a text-based front end for Dynamips. Qemu, a generic and open source machine emulator and virtualizer. VirtualBox, a free and powerful virtualization software.

GNS3 is an excellent complementary tool to real labs for network engineers, administrators and people wanting to study for certifications such as Cisco CCNA, CCNP, CCIP and CCIE as well as Juniper JNCIA, JNCIS and JNCIE.

It can also be used to experiment features of Cisco IOS, Juniper JunOS or to check configurations that need to be deployed later on real routers.

Thanks to VirtualBox integration, now even system engineers and administrators can take advantage of GNS3 to make labs and study for Redhat (RHCE, RHCT), Microsoft (MSCE, MSCA), Novell (CLP) and many other vendor certifications.

This project is an open source, free program that may be used on multiple operating systems, including Windows, Linux, and MacOS X

The main area of project :- Network addressing Routing protocols Dhcp Tftp Tunneling Vlan

Network addressingIP addresses are broken into 4 octets (IPv4) separated by dots called dotted decimal notation. An octet is a byte consisting of 8 bits. The IPv4 addresses are in the following form:192.168.10.1There are two parts of an IP address:

Network ID Host ID

The various classes of networks specify additional or fewer octets to designate the network ID versus thehost ID.When a network is set up, a netmask is also specified. The netmask determines the class of the network except for CIDR. When the netmask is setup, it specifies some number of most significant bits with a 1's value and the rest have values of 0. The most significant part of the netmask with bits set to 1's specifies the network address, and the lower part of the address will specify the host address. When setting addresses on a network, remember there can be no host address of 0 (no host address bits set), and there can be no host address with all bits set.

Class A-E networks

The addressing scheme for class A through E networks is shown below. Note: We use the 'x' character here to denote don't care situations which includes all possible numbers at the location. It is many timesused to denote networks.Network Type Address Range Normal Netmask CommentsNetwork AddressingClass A 001.x.x.x to 126.x.x.x 255.0.0.0 For very large networksClass B 128.1.x.x to 191.254.x.x 255.255.0.0 For medium size networksClass C 192.0.1.x to 223.255.254.x 255.255.255.0 For small networksClass D 224.x.x.x to 239.255.255.255 Used to support multicastingClass E 240.x.x.x to 247.255.255.255RFCs 1518 and 1519 define a system called Classless Inter-Domain Routing (CIDR) which is used to allocate IP addresses more efficiently. This may be used with subnet masks to establish networks rather than the class system shown above. A class C subnet may be 8 bits but using CIDR, it may be 12 bits.There are some network addresses reserved for private use by the Internet Assigned Numbers Authority(IANA) which can be hidden behind a computer which uses IP masquerading to

connect the private network to the internet. There are three sets of addresses reserved. These address are shown below:l 10.x.x.xl 172.16.x.x - 172.31.x.xl 192.168.x.x

Other reserved or commonly used addresses:

l 127.0.0.1 - The loopback interface address. All 127.x.x.x addresses are used by the loopbackinterface which copies data from the transmit buffer to the receive buffer of the NIC when used.l 0.0.0.0 - This is reserved for hosts that don't know their address and use BOOTP or DHCPprotocols to determine their addresses. 255 - The value of 255 is never used as an address for any part of the IP address. It is reserved forbroadcast addressing. Please remember, this is exclusive of CIDR. When using CIDR, all bits ofthe address can never be all ones.

The IPv6 Address

The IPv6 address is 128 bits, as opposed to the 32-bit IPv4 address. Also unlike IPv4, the IPv6 address is represented in hexadecimal notation, separate by colons.An example of an IPv6 address would be:1254:1532:26B1:CC14:0123:1111:2222:3333Each “grouping” (from here on called fields) of hexadecimal digits is 16 bits, with a total of eight fields. The hexadecimal values of an IPv6 address are not case-sensitive.We can drop any leading zeros in each field of an IPv6 address. For example, consider the following address:1423:0021:0C13:CC1E:3142:0001:2222:3333We can condense that address to: 1423:21:C13:CC1E:3142:1:2222:3333 Only leading zeros can be condensed. If we have an entire field comprised of zeros, we can further compact the following address:F12F:0000:0000:CC1E:2412:1111:2222:3333The condensed address would be: F12F::CC1E:2412:1111:2222:3333 Notice the double colons (::). We can only condense one set of contiguouszero fields. Thus, if we had the following address: F12F:0000:0000:CC1E:2412:0000:0000:3333We could not condense that to: F12F::CC1E:2412::3333 The address would now be ambiguous, as we wouldn’t know how many “0” fields were compacted in each spot. Remember that we can only use one set of double colons in an IPv6 address!The IPv6 PrefixIPv4 utilizes a subnet mask to define the network “prefix” and “host” portions of an address. This subnet mask can also be represented in Classless

The IPv6 Address HierarchyIPv4 separated its address space into specific classes. The class of an IPv4address was identified by the high-order bits of the first octet:

• Class A - (00000001 – 01111111, or 1 - 127)• Class B - (10000000 – 10111111, or 128 - 191)• Class C - (11000000 – 11011111, or 192 - 223)• Class D - (11100000 – 11101111, or 224 - 239)IPv6’s addressing structure is far more scalable. Less than 20% of the IPv6address space has been designated for use, currently. The potential forgrowth is enormous.The address space that has been allocated is organized into several types,determined by the high-order bits of the first field:• Special Addresses – addresses begin 00xx:• Link Local – addresses begin FE8x:• Site Local – addresses begin FECx:• Aggregate Global – addresses begin 2xxx: or 3xxx:• Multicasts – addresses begin FFxx:• Anycasts(Note: an “x” indicates the value can be any hexadecimal number)There are no broadcast addresses in IPv6. Thus, any IPv6 address that is not a multicast is a unicast address. Anycast addresses identify a group of interfaces on multiple hosts. Thus,multiple hosts are configured with an identical address. Packets sent to an anycast address are sent to the nearest (i.e., least amount of hops) host. Anycasts are indistinguishable from any other IPv6 unicast address.Practical applications of anycast addressing are a bit murky. One possible application would be a server farm providing an identical service or function, in which case anycast addressing would allow clients to connect to the nearest server.

Routing protocols We use two routing protocols in our school network :-

1.static routingConfiguring Static RoutesThe basic syntax for a static route is as follows:Router(config)# ip route [destination_network] [subnet_mask] [next-hop]Consider the following example:RouterA will have the 172.16.0.0/16 and 172.17.0.0/16 networks in its routing table as directly-connected routes. To add a static route on RouterA, pointing to the 172.18.0.0/16 network off of RouterB: RouterA(config)# ip route 172.18.0.0 255.255.0.0 172.17.1.2Notice that we point to the IP address on RouterB’s fa0/0 interface as the next-hop address. Likewise, to add a static route on RouterB, pointing to the 172.16.0.0/16 network off of RouterA:RouterB(config)# ip route 172.16.0.0 255.255.0.0 172.17.1.1 To remove a static route, simply type no in front of it: RouterA(config)# no ip route 172.18.0.0 255.255.0.0 172.17.1.2On point-to-point links, an exit-interface can be specified instead of a next hop address. Still using the previous diagram as an example:RouterA(config)# ip route 172.18.0.0 255.255.0.0 fa0/1RouterB(config)# ip route 172.16.0.0 255.255.0.0 fa0/0A static route using an exit-interface has an Administrative Distance of 0, as opposed to the default AD of 1 for static routes. An exit-interface is only functional on a point-to-point link, as there is only one possible next-hop device.

OSPF (Open Shortest Path First)OSPF is a standardized Link-State routing protocol, designed to scaleefficiently to support larger networks.OSPF adheres to the following Link State characteristics:• OSPF employs a hierarchical network design using Areas.• OSPF will form neighbor relationships with adjacent routers in the same Area.• Instead of advertising the distance to connected networks, OSPFadvertises the status of directly connected links using Link-StateAdvertisements (LSAs).• OSPF sends updates (LSAs) when there is a change to one of its links, and will only send the change in the update. LSAs are additionally refreshed every 30 minutes.• OSPF traffic is multicast either to address 224.0.0.5 (all OSPF routers) or 224.0.0.6 (all Designated Routers).• OSPF uses the Dijkstra Shortest Path First algorithm to determine the shortest path.• OSPF is a classless protocol, and thus supports VLSMs. Other characteristics of OSPF include:• OSPF supports only IP routing.• OSPF routes have an administrative distance is 110.• OSPF uses cost as its metric, which is computed based on the bandwidth of the link. OSPF has no hop-count limit.

The OSPF process builds and maintains three separate tables:

• A neighbor table – contains a list of all neighboring routers.• A topology table – contains a list of all possible routes to all knownnetworks within an area.• A routing table – contains the best route for each known network.

OSPF NeighborsOSPF forms neighbor relationships, called adjacencies, with other routers inthe same Area by exchanging Hello packets to multicast address 224.0.0.5.Only after an adjacency is formed can routers share routing information. Each OSPF router is identified by a unique Router ID. The Router ID can be determined in one of three ways:• The Router ID can be manually specified.• If not manually specified, the highest IP address configured on any Loopback interface on the router will become the Router ID.• If no loopback interface exists, the highest IP address configured on any Physical interface will become the Router ID.By default, Hello packets are sent out OSPF-enabled interfaces every 10 seconds for broadcast and point-to-point interfaces, and 30 seconds for non broadcast and point-to-multipoint interfaces. OSPF also has a Dead Interval, which indicates how long a router will waitwithout hearing any hellos before announcing a neighbor as “down.” Default for the Dead Interval is 40 seconds for broadcast and point-to-point interfaces, and 120 seconds for non-broadcast and point-to-multipoint interfaces. Notice that, by default, the dead interval timer is four times the Hello interval.These timers can be adjusted on a per interface basis:Router(config-if)# ip ospf hello-interval 15Router(config-if)# ip ospf dead-interval 60

Dynamic Host Configuration Protocol (DHCP)

This protocol is used to assign IP addresses to hosts or workstations on the network. Usually a DHCP server on the network performs this function. Basically it "leases" out address for specific times to the various hosts. If a host does not use a given address for some period of time, that IP address can then be assigned to another machine by the DHCP server.When assignments are made or changed, the DHCP server must update the information in the DNS server.As with BOOTP, DHCP uses the machine's or NIC ethernet (MAC) or hardware address to determine IP address assignments. The DHCP protocol is built on BOOTP and replaces BOOTP. DHCP extends the vendor specific area inBOOTP to 312 bytes from 64. RFC 1541 defines DHCP.DHCP RFCsDHCP RFCs are 1533, 1534, 1541, and 1542. Sent from DHCP server:l IP addressl Netmaskl Default Gateway addressl DNS server addresse(s)l NetBIOS Name server (NBNS) address(es).l Lease period in hoursl IP address of DHCP server.

DHCP Lease Stages1. Lease Request - The client sends a broadcast requesting an IP address2. Lease Offer - The server sends the above information and marks the offered address as unavailable. The message sent is a DHCPOFFER broadcast message.3. Lease Acceptance - The first offer received by the client is accepted. The acceptance is sent from the client as a broadcast (DHCPREQUEST message) including the IP address of the DNS server that sent the accepted offer.

Other DHCP servers retract their offers and mark the offered address as available and the accepted address as unavailable.4. Server lease acknowledgement - The server sends a DHCPACK or a DHCPNACK if an unavailable address was requested.DHCP discover message - The initial broadcast sent by the client to obtain a DHCP lease. It contains the client MAC address and computer name. This is a broadcast using 255.255.255.255 as the destination address and 0.0.0.0 as the source address. The request is sent, then the client waits one second for an offer. The request is repeated at 9, 13, and 16 second intervals with additional 0 to 1000 milliseconds of randomness. The attempt is repeated every 5 minutes thereafter. The client uses port 67 and the server uses port 68.DHCP Lease RenewalAfter 50% of the lease time has passed, the client will attempt to renew the lease with the original DHCP server that it obtained the lease from using a DHCPREQUEST message. Any time the client boots and the lease is 50% or more passed, DHCP the client will attempt to renew the lease. At 87.5% of the lease completion, the client will attempt to contact any DHCP server

for a new lease. If the lease expires, the client will send a request as in the initial boot when the client had no IP address. If this fails, the client TCP/IP stack will cease functioning.

Client Reservation

Client Reservation is used to be sure a computer gets the same IP address all the time. Therefore since DHCP IP addressassignments use MAC addresses to control assignments, the following are required for client reservation:l MAC (hardware) addressl IP addressExclusion RangeExclusion range is used to reserve a bank of IP addresses so computers with static IP addresses, such as servers may usethe assigned addresses in this range. These addresses are not assigned by the DHCP server.

Tftp serverTrivial File Transfer Protocol (TFTP) is a simple protocol to transfer files. It has been implemented on top of the User Datagram Protocol (UDP) using port number 69. TFTP is designed to be small and easy to implement, and therefore it lacks most of the features of a regular FTP. TFTP only reads and writes files (or mail) from/to a remote server. It cannot list directories, and currently has no provisions for user authentication.

In TFTP, any transfer begins with a request to read or write a file, which also serves to request a connection. If the server grants the request, the connection is opened and the file is sent in fixed length blocks of 512 bytes. Each data packet contains one block of data, and must be acknowledged by an acknowledgment packet before the next packet can be sent. A data packet of less than 512 bytes signals termination of a transfer. If a packet gets lost in the network, the intended recipient will timeout and may retransmit his last packet (which may be data or an acknowledgment), thus causing the sender of the lost packet to retransmit that lost packet. The sender has to keep just one packet on hand for retransmission, since the lock step acknowledgment guarantees that all older packets have been received. Notice that both machines involved in a transfer are considered senders and receivers. One sends data and receives acknowledgments, the other sends acknowledgments and receives data.

TFTP typically uses UDP as its transport protocol, but it is not a requirement. Data transfer is initiated on port 69, but the data transfer ports are chosen independently by the sender and receiver during initialization of the connection. The ports are chosen at random according to the parameters of the networking stack, typically from the range of Ephemeral ports.

TunnelingAn IP tunnel is an Internet Protocol (IP) network communications channel between two networks. It is used to transport another network protocol by encapsulation of its packets.

IP tunnels are often used for connecting two disjoint IP networks that don't have a native routing path to each other, via an underlying routable protocol across an intermediate transport network. In conjunction with the IPsec protocol they may be used to create a virtual private network between two or more private networks across a public network such as the Internet. Another prominent use is to connect islands of IPv6 installations across the IPv4 Internet.

In IP tunnelling, every IP packet, including addressing information of its source and destination IP networks, is encapsulated within another packet format native to the transit network.

At the borders between the source network and the transit network, as well as the transit network and the destination network, gateways are used that establish the end-points of the IP tunnel across the transit network. Thus, the IP tunnel endpoints become native IP routers that establish a standard IP route between the source and destination networks. Packets traversing these end-points from the transit network are stripped from their transit frame format headers and trailers used in the tunnelling protocol and thus converted into native IP format and injected into the IP stack of the tunnel endpoints. In addition, any other protocol encapsulations used during transit, such as IPsec or Transport Layer Security, are removed.

IP in IP, sometimes called ipencap, is an example of IP encapsulation within IP and is described in RFC 2003. Other variants of the IP-in-IP variety are IPv6-in-IPv4 (6in4) and IPv4-in-IPv6 (4in6).

IP tunneling often bypasses simple firewall rules transparently since the specific nature and addressing of the original datagrams are hidden. Content-control software is usually required to block IP tunnels.

Virtual LANs (VLANs)Virtual LANs (or VLANs) separate a Layer-2 switch into multiple broadcast domains. Each VLAN is its own individual broadcast domain (i.e. IP subnet). Individual ports or groups of ports can be assigned to a specific VLAN. Only ports belonging to the same VLAN can freely communicate; ports assigned to separate VLANs require a router to communicate. Broadcasts from one VLAN will never be sent out ports belonging to another VLAN.Please note: a Layer-2 switch that supports VLANs is not necessarily a Layer-3 switch. A Layer-3 switch, in addition to supporting VLANs, must also be capable of routing, and caching IP traffic flows. Layer-3 switches allow IP packets to be switched as opposed to routed, which reduces latency.

VLAN ExampleConsider the following example:Four computers are connected to a Layer-2 switch that supports VLANs.Computers A and B belong to VLAN 1, and Computers C and D belong toVLAN 2.Because Computers A and B belong to the same VLAN, they belong to the same IP subnet and broadcast domain. They will be able to communicate without the need of a router.Computers C and D likewise belong to the same VLAN and IP subnet. They also can communicate without a router. However, Computers A and B will not be able to communicate with Computers C and D, as they belong to separate VLANs, and thus separate IP subnets. Broadcasts from VLAN 1 will never go out ports configured for VLAN 2. A router will be necessary for both VLANs to communicate. Most Catalyst multi-layer switches have integrated or modular routing processors. Otherwise, an external router is required for inter-VLAN communication. By default on Cisco Catalyst switches, all interfaces belong to VLAN 1.VLAN 1 is considered the Management VLAN (by default).

Advantages of VLANs

VLANs provide the following advantages:Broadcast Control – In a pure Layer-2 environment, broadcasts are received by every host on the switched network. In contrast, each VLAN belongs to its own broadcast domain (or IP subnet); thus broadcast traffic from one VLAN will never reach another VLAN.

Security – VLANs allow administrators to “logically” separate users and departments.

Flexibility and Scalability – VLANs remove the physical boundaries of a network. Users and devices can be added or moved anywhere on the physical network, and yet remain assigned to the same VLAN. Thus, access to resources will never be interrupted.

VLAN Membership

VLAN membership can be configured one of two ways:• Statically – Individual (or groups of) switch-ports must be manually assigned to a VLAN. Any device connecting to that switch-port(s) becomes a member of that VLAN. This is a transparent process – the client device is unaware that it belongs to a specific VLAN.

• Dynamically – Devices are automatically assigned into a VLAN based on its MAC address. This allows a client device to remain in the same VLAN, regardless of which switch port the device is attached to. Cisco developed a dynamic VLAN product called the VLAN MembershipPolicy Server (VMPS). In more sophisticated systems, a user’s network account can be used to determine VLAN membership, instead of a device’s MAC address. Catalyst switches that participate in a VTP domain (explained shortly) support up to 1005 VLANs. Catalyst switches configured in VTP transparent mode support up to 4094 VLANs.

Static VLAN ConfigurationThe first step in configuring VLANs is to create the VLAN:Switch(config)# vlan 100Switch(config-vlan)# name MY_VLANThe first command creates VLAN 100, and enters VLAN configuration mode. The second command assigns the name MY_VLAN to this VLAN.Naming a VLAN is not required.The list of VLANs is stored in Flash in a database file named vlan.dat. However, information concerning which local interfaces are assigned to a specific VLAN is not stored in this file; this information is instead stored in the startup-config file of each switch. Next, an interface (or range of interfaces) must be assigned to this VLAN. The following commands will assign interface fa0/10 into the newly createdMY_VLAN.Switch(config)# interface fa0/10Switch(config-if)# switchport mode accessSwitch(config-if)# switchport access vlan 100The first command enters interface configuration mode. The second command indicates that this is an access port, as opposed to a trunk port (explained in detail shortly). The third command assigns this access port to VLAN 100. Note that the VLAN number is specified, and not the VLAN name.To view the list of VLANs, including which ports are assigned to each VLAN:Switch# show vlanVLAN Name Status Ports---- -------------------------- --------- -----------1 default active fa0/1-9,11-24100 MY_VLAN active fa0/101002 fddi- default suspended1003 token-ring -default suspended1004 fddinet -default suspended

Appendix

Dhcp

Static routing

Ipv6

Ipv6(ospf)

tftp

tunneling

Vlan

Bibliography

CCNA Study Guide v2.52 – Aaron Balchunas The CTDP Networking Guide - Mark Allen CCNA Study Guide – Todd lammle