ROUTING

A PROJECT REPORT SUBMITTED IN PARTIAL FULFILL MENT OF THE REQUIREMENT FOR THE AWARD OF THREE YEAR DIPLOMAINComputer Engineering

AMBEDKAR POLYTECHNICGOVERNMENT OF NCT OF DELHIBOARD OF TRAINING AND TECHNICAL EDUCATIONDELHI: - 110092SESSION: 2012-2015

UNDER SUPERVISION OFSUBMITTED BY:Sh. H.S BhatiaPratiyush Juyal(HOD OF C.E)BTE Roll No: - 325242

CERTIFICATE

This is to certify that ABHISHEK JHA, B.T.E. Roll No: 335265 student of Computer Engg. Third year (6th Semester), of Ambedkar Polytechnic, Shakarpur worked on project OFFICE MANAGEMENT SYSTEM From Dec 2014 to Feb 2015.He was regular in his work and devoted around 10 Weeks for the project including analysis and design. He has completed the project satisfactorily.This project has not been submitted to any other university or institution for the award of any degree.

Project GuideMr. H.S. Bhatia (HOD OF C.E)

ACKNOWLEDGEMENT

I take this opportunity to express my gratitude to my Project Guide, Mr. DINESH GULATI for his unwavering encouragement and support throughout this endeavor. His insight and expertise in this field motivated and supported me during the duration of this project. It is my privilege and honor to have worked under his supervision. His invaluable guidance and helpful discussion in every stage of this project really helped me in materialized this project. Without his constructive direction and invaluable advice, this work would not have been completed.I would also like to take this opportunity to present my sincere regards to Mr. H.S Bhatia, Head of the department (Computer Engineering) Ambedkar Polytechnic Delhi: -110092, for the support provided by him during the entire duration of diploma course and especially for this thesis. My gratitude is also extended to all teaching and non-teaching staff for their un- wavering encouragement and support in my pursuit for academics.

ABHISHEK JHABTE ROLL NO: 335265AMBEDKAR POLYTECHNIC

ABSTRACT

TheAutomated Teller Machine ATM Banking Systemis a banking application developed to perform different banking services through the Automated Teller Machines. The all functions include the regular transactions like cash deposits, cash withdrawals, balance enquiry, balance statements, savings account, and current account; change PIN Number, Credit card Withdrawals and so on. The application design maintains the information of the accounts of various customers including the information of the ATM cards, their types Credit cards, Debit Cards and the transactions done by the customers through the ATM machine centers with co-relation of the Banking Services.The stored details also include the information of the various centers in and around the ATM services, which help in the relational maintenance of every transaction in the ATM Machine by the customers with their concerned branch operations.

SELF DECLARATION OF STUDENT

This project is submitted as partial fulfillment of the requirement of DIPLOMA IN COMPUTER ENGINEERING of AMBEDKAR POLYTECHNIC SHAKARPUR NEW DELHI:-110092 affiliated to BTE DELHI, under the guidance of Mr. H.S Bhatia, Head of Computer Engineering Department, AMBEDKAR POLYTECHNIC, Shakarpur Delhi:-110092.I hereby declare that present project report on OFFICE MANAGEMENT SYSTEM is partially original and a bona fine work done by me and wherever the matter has been replicated with or without modification the same has been specially mentioned with the reasons for its usage.

ABHISHEK JHA BTE Roll No. 335265Computer EngineeringFinal Year (2015)

PROJECT OVERVIEW

The basics of routing protocols. The differences between link-state and distance vector routing protocols. The metrics used by routing protocols to determine path selection. EIGRP Router security Router backup

SOFTWARE AND HARDWARE REQUIREMENT

SOFTWARE REQUIREMENT:

OPERATING SYSTEM: MICROSOFT WINDOWS XP, VISTA,7,8.

SOFTWARE USED: CISCO PACKET TRACER.

HARDWARE REQURIMENT:

RAM: DDR2 1 GB

HARD DISK: 50GB

PROCESSOR: 1 GHZ

Software Description

CiscoPacket Traceris a 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 featuresA. The current version of Packet Tracer supports an array of simulatedApplication Layer protocols, as well as basic routing withRIP,OSPF, andEIGRP, to the extents required by the currentCCNAcurriculum. While Packet Tracer aims to provide a realistic simulation of functional networks, the application itself utilizes only a small number of features found within the actual hardware running a currentCisco IOSversion. Thus, Packet Tracer is unsuitable for modeling production networks. With the introduction of version 5.3, several new features were added, includingBGP. BGP is not part of the CCNA curriculum, but part of theCCNPcurriculum.

Packet Tracer 6.1.1 - New featuresStudent Version & Instructor Version Now there are 2 versions of Packet Tracer.Protocol ImprovementsPacket Tracer now models these new or improved features: Netflow Zone-Based Policy Firewall for IPv6 AAA Accounting Commands IPv6 CEF IPv6 IPSEC IPv6 over IPv4 GRE Tunnel Protection Etherchannel Expansion (Layer 3) IOS 15 [15.0.2-SE4(ED)] image support for 2960 OSPF - OSPFv3 Enhancements1. OSPF distance command2. "ipv6 ospf neighbor [ipv6-add]" interface subcommand3. "neighbor router-id" command4. "area [area] range" command5. ip ospf network point-to-point (loopback interface only)6. "auto-cost reference-bandwidth" EIGRP - EIGRPv6 Enhancements1. EIGRP distance command2. "debug ip eigrp summary" commands3. EIGRPv6 across FR4. EIGRP authentication commands RIP - RIPng Enhancements1. Default-information originate for RIPng2. RIP distance command update DHCP Enhancements1. DHCP for IPv62. show and clear ip dhcp conflict3. DHCP snooping commands4. IPv4 Automatic Private IP Addressing (APIPA)5. ipv6config /renew and /release on PC6. DHCPv6 commands for IOS 157. NDv6 Show Commands1. show ip route2. Show ip/ipv6 route summary Simulation Mode1. Filter based on IPv4 and IPv6 traffic2. Update PDU index in the PDU Window3. Expanded buffer for PDUs.Packet Tracer 6.0 - New features IOS 15 HWIC-2T and HWIC-8A modules 3 new cisco routers (Cisco 1941, Cisco 2901, Cisco 2911) HSRP support Activity Wizard and Variable Manager improvement BGP configurations

Use in educationPacket Tracer is commonly used by Cisco Networking Academy students working towards Cisco Certified Network Associate (CCNA) certification. Due to functional limitations, it is intended by Cisco to be used only as a learning aid, not a replacement for Ciscoroutersandswitches. Packet Tracer can be used to understand various concepts of networking with simulation, It can be used to design a network by connecting various networking devices and running various troubleshooting tests to check the connectivity and communication between different networking devices. Packet Tracer can be used to understand the use of different networking devices appropriately and the difference in their working. As it is costly to buy various networking equipment while learning networking, Packet Tracer can be used to understand computer networks.

Routing BasicsThis chapter introduces the underlying concepts widely used in routing protocols. Topics summarized here include routing protocol components and algorithms. In addition, the role of routing protocols is briefly contrasted with the role of routed or network protocols. Subsequent chapters in Part VII, "Routing Protocols," address specific routing protocols in more detail, while the network protocols that use routing protocols are discussed in Part VI, "Network Protocols." What Is Routing? Routing is the act of moving information across an internetwork from a source to a destination. Along the way, at least one intermediate node typically is encountered. 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 link layer) of the OSI reference model, whereas routing occurs at Layer 3 (the network layer). This distinction provides routing and bridging with different information to use in the process of moving information from source to destination, so the two functions accomplish their tasks in different ways. The topic of routing has been covered in computer science literature for more than two decades, but routing achieved commercial popularity as late as the mid-1980s. The primary reason for this time lag is that networks in the 1970s were simple, homogeneous environments. Only relatively recently has large-scale internetworking has become popular.Routing Components Routing involves two basic activities: determining optimal routing paths and transporting information groups (typically called packets) through an internetwork. In the context of the routing process, the latter of these is referred to as packet switching. Although packet switching is relatively straightforward, path determination can be very complex.

Path Determination 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, that is used by routing algorithms to determine the optimal path to a destination. To aid the process of path determination, routing algorithms initialize and maintain routing tables, which contain route information. Route information varies depending on the routing algorithm used. Routing algorithms fill routing tables with a variety of information. Destination/next hop associations tell a router that a particular destination can be reached optimally by sending the packet to a particular router representing the "next hop" on the way to the final destination. When a router receives an incoming packet, it checks the destination address and attempts to associate this address with a next hop.Design Goals Routing algorithms often have one or more of the following design goals: Optimality Simplicity and low overhead Robustness and stability Rapid convergence Flexibility INTRODUCTION TO COMPUTER NETWORKING:Computer networks were invented to connect computers together to allow them to share resources such as files and printers. Of course, networks have been around for quite some time. Early network implementations were proprietary (because there was nothing else). The networking capability was written into the application (an accounting system for example), and the choice of network protocol (communications software) and hardware was hard-coded into the application package. But this created problems. If the user or manufacturer wanted to change any of the networking components, the core application had to be rewritten. When networking really took off, it seemed that there was a protocol flavor-of-the-month. Things were changing so fast that it became impractical for application vendors to keep up. There had to be a better way.In response to this problem, engineers developed the open systems interconnect (OSI) layer model for networking. This layered model allows the application (an accounting program, editing application, etc.) to remain separate from the layers below. This way, software protocols and hardware can be upgraded without having to rewrite the overarching applications. The application then interacts with the protocols through a software interface called an application programming interface (API). Standardization of the API allowed manufacturers to substitute different technology at lower layers without having to overhaul their applications.

Figure 1. Simplified layered model. .

The layered model in Figure 1 illustrates another fundamental concept in networking. Note that the protocols are a separate layer from the physical layer. This allows a given networking technology such as Ethernet to be implemented over different physical media. For example, users could implement Ethernet using unshielded twisted pair (UTP) or optical fiber. In fact, these different physical media types could be mixed within a network. The signals riding on these different media types are Ethernet. The layered approach to networking makes this possible.It also is possible to select protocols independently from the physical hardware upon which these protocols are transported. For example, both Ethernet and Fiber Channel can be carried on fiber.There are many variations of the OSI model. The most common has seven layers: physical, data link, network, transport, session, presentation and application. While it is not important to understand what all these layers do, you should know that there are fundamental differences in how network signals are moved, and that many of these differences center on whether switching decisions are made at Layer 2 or Layer 3. It is not always possible to make a clear distinction between the different layers. There are many excellent OSI model tutorials available on the Internet.Network protocolsThe two dominant networking technologies these days are Ethernet and Fiber Channel. Ethernet, a packet-based networking technology, has by far the largest technological deployment. Data from an application is sent to the protocol layers. In these layers, the data is chopped up into packets. Next, a destination address is put on the front of the packet, and the packet is sent to the physical layer for transportation on the network.

Figure 2. Simplified Ethernet packet.

Figure 2 shows a simplified Ethernet packet. Thousands of these potential Ethernet packets are generated by a computer each second and shipped across the network, each packet traveling independently. The address on the packet allows the network to route the packet to its destination. The protocol layer at the destination computer is responsible for reassembling the packets in the proper order and presenting the application with the original data.Ethernet is used ubiquitously both for intranets (networks that are local to a given facility), and on the Internet. The Internet (capital I) is comprised of a large number of networks and switching technology that allows computers to send data across the country or around the world. While the switching and scope of these networks is vastly different from that of an intranet, the basic Ethernet packet remains unchanged. In fact, usually the same Ethernet packet travels across a local intranet, through a gateway computer and on to the Internet.

There are many different Ethernet topologies. Topology refers to how computers in the network are connected together. The most common topology is called hub-and-spoke, in which each computer has a single, dedicated Ethernet connection to a central Ethernet switch. Computer A is transferring files to Computer B it can do this at full speed while Computer C is transferring files to Computer D.A star network is easy to build and troubleshoot, and it can provide high bandwidth to the desktop if it is designed properly. But there are caveats. To get the maximum bandwidth between devices connected to the network, the switch itself must have the capacity to operate at double the bandwidth of the individual connections to the computers. In our example, if this is a 100Mb/s network, the switch must have at least 200Mb/s of available bandwidth.Fiber Channel is a computer network that is frequently confused with Ethernet. They are two separate and incompatible technologies created to solve different problems. The confusion arises because they both can run on the same physical network. It looks as if you can just plug a Fiber Channel cable into an Ethernet fiber switch. But this will not work. The two networks use fundamentally different protocols or language to talk, and they come from different origins. Fiber Channel was created to connect computers to disk drives. In the early days of computing, there were strict limits on how far the disk drive could be physically located from the computer itself. Remember, CPUs sat in one box, and storage sat in another box. As computers got faster, they needed faster connections to the disk drives that served them. Parallel connections to drives became the norm. But this too reached a practical limit as the lengths of parallel cables started to give rise to termination problems, RF crosstalk, and poor frequency response. Computer designers needed a cable extender for disk drives that could be easily supported on existing systems. At this time, the Small Computer System Interface, or SCSI, was being used for many high-performance drives. Network engineers went to work designing a computer network that could transport SCSI commands. They came up with Fiber Channel a network that established virtual connections between devices, allowing the robust transmission of SCSI commands across virtually unlimited distances. Now, Fiber Channel is the predominant local network in use for the connection of high-speed peripherals to computers.CLASSIFICATION OF NETWORKING TECHNOLOGY:There are about eight types of network which are used worldwide these days, both in houses and commercially. These networks are used on the bases of their scale and scope, historical reasons, preferences for networking industries, and their design and implementation issues. LAN and WAN are mostly known and used widely. LAN, local area network was first invented for communication between two computers. LAN operates through cables and network cards. Later WLAN, Wireless local area network was formed through LAN concept, there are no wires involved in communication between computers, and Wireless LAN cards are required to connect to wireless network. LAN is the original network out of which other networks are formed according to requirements. They are as follow.LAN - Local Area Network WLAN - Wireless Local Area Network WAN - Wide Area Network MAN - Metropolitan Area Network SAN - Storage Area Network, It can also refer with names like System Area Network, Server Area Network, or sometimes Small Area Network CAN - Campus Area Network, Controller Area Network, and often Cluster Area Network PAN - Personal Area Network DAN - Desk Area Network LAN - Local Area Network LAN connects networking devices with in short spam of area, i.e. small offices, home, internet cafes etc. LAN uses TCP/IP network protocol for communication between computers. It is often but not always implemented as a single IP subnet. Since LAN is operated in short area so it can be control and administrate by single person or organization.WAN - Wide Area NetworkAs word Wide implies, WAN, wide area network cover large distance for communication between computers. The Internet itself is the biggest example of Wide area network, WAN, which is covering the entire earth. WAN is distributed collection of geographically LANs. A network connecting device router connects LANs to WANs. WAN used network protocols like ATM, X.25, and Frame Relay for long distance connectivity.Wireless - Local Area Network A LAN, local area network based on wireless network technology mostly referred as Wi-Fi. Unlike LAN, in WLAN no wires are used, but radio signals are the medium for communication. Wireless network cards are required to be installed in the systems for accessing any wireless network around. Mostly wireless cards connect to wireless routers for communication among computers or accessing WAN, internet.MAN - Metropolitan Area NetworkThis kind of network is not mostly used but it has its own importance for some government bodies and organizations on larger scale. MAN, metropolitan area network falls in middle of LAN and WAN, It covers large span of physical area than LAN but smaller than WAN, such as a city.CAN - Campus Area NetworkNetworking spanning with multiple LANs but smaller than a Metropolitan area network, MAN. This kind of network mostly used in relatively large universities or local business offices and buildings.SAN - Storage Area NetworkSAM technology is used for data storage and it has no use for most of the organization but data oriented organizations. Storage area network connects servers to data storage devices by using Fiber channel technology. SAN - System Area NetworkSAN, system area networks are also known as cluster area network and it connects high performance computers with high speed connections in cluster configurationNETWORK ARCHITECTURE PLANNING:Network DesignThe experienced Tellabs engineering staff, combined with world class Tools and processes, offers end-to-end design expertise and helps to Eliminate costly errors and redesigns. Utilizing the high-level design Produced in the Network Architecture Service, Tellabs senior Engineers develop a complete, implementation-ready engineering Design package documenting the configuration parameters for Tell labs equipment at specific sites. By partnering with Tellabs for your detailed network design, you are able to take advantage of our expert resources and produce a comprehensive design solution that achieves your objectives while utilizing knowledge from past implementations and industry Best practices. The Engineering Design Package includes: Detailed fiber maps Detailed ring diagrams Fiber characterization reports Optical power budgets Equipment elevations Naming conventions (site names, node names, circuit IDs) IP addressing for network management applications System installation requirements System integration requirements Transponder placement and configuration data Wavelength cross-connect and configuration data L2 or L3 traffic parameters Detailed Network Management System (NMS) information Progress reports and project documentation Architecture and Design Services Portfolio

NETWORK ARCHITECTURE SERVICES:Network topology, traffic and capacity patternsNetwork implementation outlineOutline of the business and operational implicationsManagement reporting packagesNetwork Design ServiceSystem commissioning dataDetailed equipment lists and naming conventionsSystem installation requirementsSystem integration requirementsAchieve Your ObjectivesACHIEVE YOUR OBJECTIVES:Minimize cost of ownership Maximize returns with minimalInvestmentsAccelerate time-to-market Bypass the learning curve and speed up your ability to generate revenueSustain competitive advantage ensure a cost-effective foundation for daily operations that delivers superior performance and intelligent growth.

FUNDAMENTALS OF INTERNETWIOKING:What Is an Internetwork?An internetwork is a collection of individual networks, connected by intermediate networking devices, that functions as a single large network. Internetworking refers to the industry, products, and procedures that meet the challenge of creating and administering internetworks. Figure 1-1 illustrates some different kinds of network technologies that can be interconnected by routers and other networking devices to create an internetwork.Internetworking ChallengesImplementing a functional internetwork is no simple task. Many challenges must be faced, especially in the areas of connectivity, reliability, network management, and flexibility. Each area is key in establishing an efficient and effective internetwork. The challenge when connecting various systems is to support communication among disparate technologies. Different sites, for example, may use different types of media operating at varying speeds, or may even include different types of systems that need to communicate. Because companies rely heavily on data communication, internetworks must provide a certain level of reliability. This is an unpredictable world; so many large internetworks include redundancy to allow for communication even when problems occur. Furthermore, network management must provide centralized support and troubleshooting capabilities in an internetwork. Configuration, security, performance, and other issues must be adequately addressed for the internetwork to function smoothly. Security within an internetwork is essential. Many people think of network security from the perspective of protecting the private network from outside attacks. However, it is just as important to protect the network from internal attacks, especially because most security breaches come from inside. Networks must also be secured so that the internal network cannot be used as a tool to attack other external sites. Early in the year 2000, many major web sites were the victims of distributed denial of service (DDOS) attacks. These attacks were possible because a great number of private networks currently connected with the Internet were not properly secured. These private networks were used as tools for the attackers.

Internetworking ChallengesImplementing a functional internetwork is no simple task. Many challenges must be faced, especially in the areas of connectivity, reliability, network management, and flexibility. Each area is key in establishing an efficient and effective internetwork. The challenge when connecting various systems is to support communication among disparate technologies. Different sites, for example, may use different types of media operating at varying speeds, or may even include different types of systems that need to communicate. Because companies rely heavily on data communication, internetworks must provide a certain level of reliability. This is an unpredictable world so many large internetworks include redundancy to allow for communication even when problems occur. Furthermore, network management must provide centralized support and troubleshooting capabilities in an internetwork. Configuration, security, performance, and other issues must be adequately addressed for the internetwork to function smoothly. Security within an internetwork is essential. Many people think of network security from the perspective of protecting the private network from outside attacks. However, it is just as important to protect the network from internal attacks, especially because most security breaches come from inside. Networks must also be secured so that the internal network cannot be used as a tool to attack other external sites. Early in the year 2000, many major web sites were the victims of distributed denial of service (DDOS) attacks. These attacks were possible because a great number of private networks currently connected with the Internet were not properly secured. These private networks were used as tools for the attackers. Because nothing in this world is stagnant, internetworks must be flexible enough to change with new demands.

Figure 1-1 Different Network Technologies Can Be Connected to Create an Internetwork.

Open System Interconnection Reference Model.The Open System Interconnection (OSI) reference model describes how information from a software application in one computer moves through a network medium to a software application in another computer. The OSI reference model is a conceptual model composed of seven layers, each specifying particular network functions. The model was developed by the International Organization for Standardization (ISO) in 1984, and it is now considered the primary architectural model for intercomputer communications. The OSI model divides the tasks involved with moving information between networked computers into seven smaller, more manageable task groups. A task or group of tasks is then assigned to each of the seven OSI layers. Each layer is reasonably self-contained so that the tasks assigned to each layer can be implemented independently. This enables the solutions offered by one layer to be updated without adversely affecting the other layers. The following list details the seven layers of the Open System Interconnection (OSI) reference model:1. Layer 7Application2. Layer 6Presentation3. Layer 5Session4. Layer 4Transport5. Layer 3Network6. Layer 2Data link7. Layer 1Physical

Characteristics of the OSI LayersThe seven layers of the OSI reference model can be divided into two categories: upper layers and lower layers. The upper layers of the OSI model deal with application issues and generally are implemented only in software. The highest layer, the application layer, is closest to the end user. Both users and application layer processes interact with software applications that contain a communications component. The term upper layer is sometimes used to refer to any layer above another layer in the OSI model. The lower layers of the OSI model handle data transport issues. The physical layer and the data link layer are implemented in hardware and software. The lowest layer, the physical layer, is closest to the physical network medium (the network cabling, for example) and is responsible for actually placing information on the medium.Figure 1-3 illustrates the division between the upper and lower OSI layers.

Protocols:The OSI model provides a conceptual framework for communication between computers, but the model itself is not a method of communication. Actual communication is made possible by using communication protocols. In the context of data networking, a protocol is a formal 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 communication protocols exist. Some of these protocols include LAN protocols, WAN protocols, network protocols, and routing protocols. LAN protocols operate at the physical and data link layers of the OSI model and define communication over the various LAN media. WAN protocols operate at the lowest three layers of the OSI model and define communication over the various wide-area media.Routing protocols are network layer protocols that are responsible for exchanging information between routers so that the routers can select the proper path for network traffic. Finally, network protocols are the various upper-layer protocols that exist in a given protocol suite. Many protocols rely on others for operation. For example, many routing protocols use network protocols to exchange information between routers. This concept of building upon the layers already in existence is the foundation of the OSI model.OSI Model and Communication Between SystemsInformation being transferred from a software application in one computer system to a software application in another must pass through the OSI layers. For example, if a software application in System A has information to transmit to a software application in System B, the application program in System A will pass its information to the application layer (Layer 7) of System A. The application layer then passes the information to the presentation layer (Layer 6), which relays the data to the session layer (Layer 5), and so on down to the physical layer (Layer 1). At the physical layer, the information is placed on the physical network medium and is sent across the medium to System B. The physical layer of System B removes the information from the physical medium, and then its physical layer passes the information up to the data link layer (Layer 2), which passes it to the network layer (Layer 3), and so on, until it reaches the application layer (Layer 7) of System B. Finally, the application layer of System By passes the information to the recipient application program to complete the communication process.Interaction between OSI Model LayersA given layer in the OSI model generally communicates with three other OSI layers: the layer directly above it, the layer directly below it, and its peer layer in other networked computer systems. The data link layer in System A, for example, communicates with the network layer of System A, the physical layer of System A, and the data link layer in System B. Figure 1-4 illustrates this example.

OSI Model Layers and Information ExchangeThe seven OSI layers use various forms of control information to communicate with their peer layers in other computer systems. This control information consists of specific requests and instructions that are exchanged between peer OSI layers. Control information typically takes one of two forms: headers and trailers. Headers are prepended to data that has been passed down from upper layers. Trailers are appended to data that has been passed down from upper layers. An OSI layer is not required to attach a header or a trailer to data from upper layers. Headers, trailers, and data are relative concepts, depending on the layer that analyzes the information unit. At the network layer, for example, an information unit consists of a Layer 3 header and data. At the data link layer, however, all the information passed down by the network layer (the Layer 3 header and the data) is treated as data. In other words, the data portion of an information unit at a given OSI layer potentially can contain headers, trailers, and data from all the higher layers. This is known as encapsulation. Figure1-6 shows how the header and data from one layer are encapsulated into the header of the next lowest layer.

Information Exchange ProcessThe information exchange process occurs between peer OSI layers. Each layer in the source system adds control information to data, and each layer in the destination system analyzes and removes the control information from that data. If System A has data from a software application to send to System B, the data is passed to the application layer. The application layer in System A then communicates any control information required by the application layer in System B by prepending a header to the data. The resulting information unit (a header and the data) is passed to the presentation layer, which prepends its own header containing control information intended for the presentation layer in System B. The information unit grows in size as each layer prepends its own header (and, in some cases, a trailer) that contains control information to be used by its peer layer in System B. At the physical layer, the entire information unit is placed onto the network medium. The physical layer in System B receives the information unit and passes it to the data link layer. The data link layer in System B then reads the control information contained in the header prepended by the data link layer in System A. The header is then removed, and the remainder of the information unit is passed to the network layer. Each layer performs the same actions: The layer reads the header from its peer layer, strips it off, and passes the remaining information unit to the next highest layer. After the application layer performs these actions, the data is passed to the recipient software application in System B, in exactly the form in which it was transmitted by the application in System A.OSI Model Physical Layer:The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems. Physical layer specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. Physical layer implementations can be categorized as either LAN or WAN specifications. Figure 1-7 illustrates some common LAN and WAN physical layer implementations

OSI Model Data Link Layer: The data link layer provides reliable transit of data across a physical network link. Different data link layer specifications define different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control. Physical addressing (as opposed to network addressing) defines how devices are addressed at the data link layer. Network topology consists of the data link layer specifications that often define how devices are to be physically connected, such as in a bus or a ring topology. Error notification alerts upper-layer protocols that a transmission error has occurred, and the sequencing of data frames reorders frames that are transmitted out of sequence. Finally, flow control moderates the transmission of data so that the receiving device is not overwhelmed with more traffic than it can handle at one time.The Institute of Electrical and Electronics Engineers (IEEE) has subdivided the data link layer into two sub layers: Logical Link Control (LLC) and Media Access Control (MAC). Figure 1-8 illustrates the IEEE sub layers of the data link layer.

The Logical Link Control (LLC) sub layer of the data link layer manages communications between devices over a single link of a network. LLC is defined in the IEEE 802.2 specification and supports both connectionless and connection-oriented services used by higher-layer protocols. IEEE 802.2 defines a number of fields in data link layer frames that enable multiple higher-layer protocols to share a single physical data link. OSI Model Network LayerThe network layer defines the network address, which differs from the MAC address. Some network layer implementations, such as the Internet Protocol (IP), define network addresses in a way that route selection can be determined systematically by comparing the source network address with the destination network address and applying the subnet mask. Because this layer defines the logical network layout, routers can use this layer to determine how to forward packets. Because of this, much of the design and configuration work for internetworks happens at Layer 3, the network layer.OSI Model Transport Layer: The transport layer accepts data from the session layer and segments the data for transport across the network. Generally, the transport layer is responsible for making sure that the data is delivered error-free and in the proper sequence. Flow control generally occurs at the transport layer. Flow control manages data transmission between devices so that the transmitting device does not send more data than the receiving device can process. Multiplexing enables data from several applications to be transmitted onto a single physical link. Virtual circuits are established, maintained, and terminated by the transport layer. Error checking involves creating various mechanisms for detecting transmission errors, while error recovery involves acting, such as requesting that data be retransmitted, to resolve any errors that occur. The transport protocols used on the Internet are TCP and UDP.OSI Model Session Layer: The session layer establishes, manages, and terminates communication sessions. Communication sessions consist of service requests and service responses that occur between applications located in different network devices. These requests and responses are coordinated by protocols implemented at the session layer. Some examples of session-layer implementations include Zone Information Protocol (ZIP), the AppleTalk protocol that coordinates the name binding process; and Session Control Protocol (SCP), the DECnet Phase IV session layer protocol.OSI Model Presentation Layer: The presentation layer provides a variety of coding and conversion functions that are applied to application layer data. These functions ensure that information sent from the application layer of one system would be readable by the application layer of another system. Some examples of presentation layer coding and conversion schemes include common data representation formats, conversion of character representation formats, common data compression schemes, and common data encryption schemes. Common data representation formats, or the use of standard image, sound, and video formats, enable the interchange of application data between different types of computer systems. Conversion schemes are used to exchange information with systems by using different text and data representations, such as EBCDIC and ASCII. Standard data compression schemes enable data that is compressed at the source device to be properly decompressed at the destination. Standard data encryption schemes enable data encrypted at the source device to be properly deciphered at the destination. Presentation layer implementations are not typically associated with a particular protocol stack. Some well-known standards for video include QuickTime and Motion Picture Experts Group (MPEG).QuickTime is an Apple Computer specification for video and audio, and MPEG is a standard for video compression and coding. Among the well-known graphic image formats are Graphics Interchange Format (GIF), Joint Photographic Experts Group (JPEG), and Tagged Image File Format (TIFF). GIF is a standard for compressing and coding graphic images. JPEG is another compression and coding standard for graphic images, and TIFF is a standard coding format for graphic images.OSI Model Application Layer: The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer. Some examples of application layer implementations include Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP).

Information Formats: The data and control information that is transmitted through internetworks takes a variety of forms. The terms used to refer to these information formats are not used consistently in the internetworking industry but sometimes are used interchangeably. Common information formats include frames, packets, datagrams, segments, and messages, cells, and data units. A frame is an information unit whose source and destination are data link layer entities. A frame is composed of the data link layer header (and possibly a trailer) and upper-layer data. The header and trailer contain control information intended for the data link layer entity in the destination system. Data from upper-layer entities is encapsulated in the data link layer header and trailer. Figure 1-9 illustrates the basic components of a data link layer frame.

A packet is an information unit whose source and destination are network layer entities. A packet is composed of the network layer header (and possibly a trailer) and upper-layer data. The header and trailer contain control information intended for the network layer entity in the destination system. Data from upper-layer entities is encapsulated in the network layer header and trailer. Figure 1-10 illustrates the basic components of a network layer packet.

The term datagram usually refers to an information unit whose source and destination are network layer entities that use connectionless network service. The term segment usually refers to an information unit whose source and destination are transport layer entities. A message is an information unit whose source and destination entities exist above the network layer (often at the application layer).A cell is an information unit of a fixed size whose source and destination are data link layer entities. Cells are used in switched environments, such as Asynchronous Transfer Mode (ATM) and SwitchedMultimegabit Data Service (SMDS) networksA cell is composed of the header and payload. The header contains control information intended for the destination data link layer entity and is typically 5 bytes long. The payload contains upper-layer data that is encapsulated in the cell header and is typically 48 bytes long. The length of the header and the payload fields always are the same for each cell. Figure 1-11 depicts the components of a typical cell.

Data unit is a generic term that refers to a variety of information units. Some common data units are service data units (SDUs), protocol data units, and bridge protocol data units (BPDUs). SDUs are information units from upper-layer protocols that define a service request to a lower-layer protocol. PDU is OSI terminology for a packet. BPDUs are used by the spanning-tree algorithm as hello messages.ISO Hierarchy of Networks: Large networks typically are organized as hierarchies. A hierarchical organization provides such advantages as ease of management, flexibility, and a reduction in unnecessary traffic. Thus, the International Organization for Standardization (ISO) has adopted a number of terminology conventions for addressing network entities. Key terms defined in this section include end system (ES), intermediate system (IS), area, and autonomous system (AS). An ES is a network device that does not perform routing or other traffic forwarding functions. Typical ESs includes such devices as terminals, personal computers, and printers. An IS is a network device that performs routing or other traffic-forwarding functions. Typical ISs include such devices as routers, switches, and bridges. Two types of IS networks exist: intra domain IS and inter domain IS. An intradomain IS communicates within a single autonomous system, while an intradomain IS communicates within and between autonomous systems. An area is a logical group of network segments and their attached devices. Areas are subdivisions of autonomous systems (ASs). An AS is a collection of networks under a common administration that share a common routing strategy. Autonomous systems are subdivided into areas, and an AS is sometimes called a domain. Figure 1-12 illustrates a hierarchical network and its components.

Connection-Oriented and Connectionless Network ServicesIn general, transport protocols can be characterized as being either connection-oriented or connectionless. Connection-oriented services must first establish a connection with the desired service before passing any data. A connectionless service can send the data without any need to establish a connection first. In general, connection-oriented services provide some level of delivery guarantee, whereas connectionless services do not. Connection-oriented service involves three phases: connection establishment, data transfer, and connection termination.During connection establishment, the end nodes may reserve resources for the connection. The end nodes also may negotiate and establish certain criteria for the transfer, such as a window size used inTCP connections: This resource reservation is one of the things exploited in some denial of service (DOS) attacks. An attacking system will send many requests for establishing a connection but then will never complete the connection. The attacked computer is then left with resources allocated for many never-completed connections. Then, when an end node tries to complete an actual connection, there are not enough resources for the valid connection. The data transfer phase occurs when the actual data is transmitted over the connection. During data transfer, most connection-oriented services will monitor for lost packets and handle resending them. The protocol is generally also responsible for putting the packets in the right sequence before passing the data up the protocol stack. When the transfer of data is complete, the end nodes terminate the connection and release resources reserved for the connection. Connection-oriented network services have more overhead than connectionless ones. Connection-oriented services must negotiate a connection, transfer data, and tear down the connection, whereas a connectionless transfer can simply send the data without the added overhead of creating and tearing down a connection. Each has its place in internetworks.

Internetwork AddressingInternetwork addresses identify devices separately or as members of a group. Addressing schemes vary depending on the protocol family and the OSI layer. Three types of internetwork addresses are commonly used: data link layer addresses, Media Access Control (MAC) addresses, and network layer addresses.Data Link Layer AddressesA data link layer address uniquely identifies each physical network connection of a network device. Data-link addresses sometimes are referred to as physical or hardware addresses. Data-link addresses usually exist within a flat address space and have a pre-established and typically fixed relationship to a specific device. End systems generally have only one physical network connection and thus have only one data-link address. Routers and other internetworking devices typically have multiple physical network connections and therefore have multiple data-link addresses. Figure 1-13 illustrates how each interface on a device is uniquely identified by a data-link address.

MAC AddressesMedia Access Control (MAC) addresses consist of a subset of data link layer addresses. MAC addresses identify network entities in LANs that implement the IEEE MAC addresses of the data link layer. As with most data-link addresses, MAC addresses are unique for each LAN interface. Figure 1-14 illustrates the relationship between MAC addresses, data-link addresses, and the IEEE sub layers of the data link layer.

MAC addresses are 48 bits in length and are expressed as 12 hexadecimal digits. The first 6 hexadecimal digits, which are administered by the IEEE, identify the manufacturer or vendor and thus comprise the Organizationally Unique Identifier (OUI). The last 6 hexadecimal digits comprise the interface serial number, or another value administered by the specific vendor. MAC addresses sometimes are called burned-in addresses (BIAs) because they are burned into read-only memory (ROM) and are copied into random-access memory (RAM) when the interface card initializes. Figure 1-15 illustrates the

Mapping Addresses: Because internetworks generally use network addresses to route traffic around the network, there is a need to map network addresses to MAC addresses. When the network layer has determined the destination stations network address, it must forward the information over a physical network using a MAC address. Different protocol suites use different methods to perform this mapping, but the most popular is Address Resolution Protocol (ARP). Different protocol suites use different methods for determining the MAC address of a device. The following three methods are used most often. Address Resolution Protocol (ARP) maps network addresses to MAC addresses. The Hello protocol enables network devices to learn the MAC addresses of other network devices. MAC addresses either are embedded in the network layer address or are generated by an algorithm. Address Resolution Protocol (ARP) is the method used in the TCP/IP suite. When a network device needs to send data to another device on the same network, it knows the source and destination network addresses for the data transfer. It must somehow map the destination address to a MAC address before forwarding the data. First, the sending station will check its ARP table to see if it has already discovered this destination stations MAC address. If it has not, it will send a broadcast on the network with the destination stations IP address contained in the broadcast. Every station on the network receives the broadcast and compares the embedded IP address to its own. Only the station with the matching IP address replies to the sending station with a packet containing the MAC address for the station. The first station then adds this information to its ARP table for future reference and proceeds to transfer the data. When the destination device lies on a remote network, one beyond a router, the process is the same except that the sending station sends the ARP request for the MAC address of its default gateway. It then forwards the information to that device. The default gateway will then forward the information over whatever networks necessary to deliver the packet to the network on which the destination device resides. The router on the destination devices network then uses ARP to obtain the MAC of the actual destination device and delivers the packet.The Hello protocol is a network layer protocol that enables network devices to identify one another and indicate that they are still functional. When a new end system powers up, for example, it broadcasts hello messages onto the network. Devices on the network then return hello replies, and hello messages are also sent at specific intervals to indicate that they are still functional. Network devices can learn the MAC addresses of other devices by examining Hello protocol packets. Three protocols use predictable MAC addresses. In these protocol suites, MAC addresses are predictable because the network layer either embeds the MAC address in the network layer address or uses an algorithm to determine the MAC address. The three protocols are Xerox Network Systems (XNS), Novell Internetwork Packet Exchange (IPX), and DEC net Phase IV.Network Layer Addresses: A network layer address identifies an entity at the network layer of the OSI layers. Network addresses usually exist within a hierarchical address space and sometimes are called virtual or logical addresses. The relationship between a network address and a device is logical and unfixed; it typically is based either on physical network characteristics (the device is on a particular network segment) or on groupings that have no physical basis (the device is part of an AppleTalk zone). End systems require one network layer address for each network layer protocol that they support. (This assumes that the device has only one physical network connection.) Routers and other internetworking devices require one network layer address per physical network connection for each network layer protocol supported. For example, a router with three interfaces each running AppleTalk, TCP/IP, and OSI must have three network layer addresses for each interface. The router therefore has nine network layer addresses. Figure 1-16 illustrates how each network interface must be assigned a network address for each protocol supported.

Hierarchical versus Flat Address Space: Internetwork address space typically takes one of two forms: hierarchical address space or flat address space. A hierarchical address space is organized into numerous subgroups, each successively narrowing an address until it points to a single device (in a manner similar to street addresses). A flat address space is organized into a single group (in a manner similar to U.S. Social Security numbers).Hierarchical addressing offers certain advantages over flat-addressing schemes. Address sorting and recall is simplified using comparison operations. For example, Ireland in a street address eliminates any other country as a possible location. Figure 1-17 illustrates the difference between hierarchical and flat address spaces.Address Assignments: Addresses are assigned to devices as one of two types: static and dynamic. Static addresses are assigned by a network administrator according to a preconceived internetwork addressing plan. A static address does not change until the network administrator manually changes it. Dynamic addresses are obtained by devices when they attach to a network, by means of some protocol-specific process. A device using dynamic address often has a different address each time that it connects to the network. Some networks use a server to assign addresses. Server-assigned addresses are recycled for reuse as devices disconnect. A device is therefore likely to have a different address each time that it connects to the network.Addresses versus Names: Internetwork devices usually have both a name and an address associated with them. Internetwork names typically are location-independent and remain associated with a device wherever that device moves (for example, from one building to another). Internetwork addresses usually are location-dependent and change when a device is moved (although MAC addresses are an exception to this rule). As with network addresses being mapped to MAC addresses, names are usually mapped to network addresses through some protocol. The Internet uses Domain Name System (DNS) to map the name of a device to its IP address. For example, its easier for you to remember www.cisco.com instead of some IP address. Therefore, you type www.cisco.com into your browser when you want to access Ciscos web site. Your computer performs a DNS lookup of the IP address for Ciscos web server and then communicates with it using the network address.

Standards Organizations:A wide variety of organizations contribute to internetworking standards by providing forums for discussion, turning informal discussion into formal specifications, and proliferating specifications after they are standardized. Most standards organizations create formal standards by using specific processes: organizing ideas, discussing the approach, developing draft standards, voting on all or certain aspects of the standards, and then formally releasing the completed standard to the public. Some of the best-known standards organizations that contribute to internetworking standards include these: International Organization for Standardization (ISO)ISO is an international standards organization responsible for a wide range of standards, including many that are relevant to networking. Its best-known contribution is the development of the OSI reference model and the OSI protocol suite. American National Standards Institute (ANSI)ANSI, which is also a member of the ISO, is the coordinating body for voluntary standards groups within the United States. ANSI developed the Fiber Distributed Data Interface (FDDI) and other communications standards. Electronic Industries Association (EIA)EIA specifies electrical transmission standards, including those used in networking. The EIA developed the widely used EIA/TIA-232 standard (formerly known as RS-232). Institute of Electrical and Electronic Engineers (IEEE)IEEE is a professional organization that defines networking and other standards. The IEEE developed the widely used LAN standardsIEEE 802.3 and IEEE 802.5 International Telecommunication Union Telecommunication Standardization Sector(ITU-T)Formerly called the Committee for International Telegraph and Telephone (CCITT),ITU-T is now an international organization that develops communication standards. The ITU-T developed X.25 and other communications standards. Internet Activities Board (IAB)IAB is a group of internetwork researchers who discuss issues pertinent to the Internet and set Internet policies through decisions and task forces.

NETWORK MANAGEMENTWhat Is Network Management?Network management means different things to different people. In some cases, it involves a solitary network consultant monitoring network activity with an outdated protocol analyzer. In other cases, network management involves a distributed database, auto polling of network devices, and high-end workstations generating real-time graphical views of network topology changes and traffic. In general, network management is a service that employs a variety of tools, applications, and devices to assist human network managers in monitoring and maintaining networks.

A Historical PerspectiveThe early 1980s saw tremendous expansion in the area of network deployment. As companies realized the cost benefits and productivity gains created by network technology, they began to add networks andexpand existing networks almost as rapidly as new network technologies and products were introduced. By the mid-1980s, certain companies were experiencing growing pains from deploying many different (and sometimes incompatible) network technologies.The problems associated with network expansion affect both day-to-day network operation management and strategic network growth planning. Each new network technology requires its own set of experts. In the early 1980s, the staffing requirements alone for managing large, heterogeneous networks created a crisis for many organizations. An urgent need arose for automated network management (including what is typically called network capacity planning) integrated across diverse environments.Network Management ArchitectureMost network management architectures use the same basic structure and set of relationships. End Stations (managed devices), such as computer systems and other network devices, run software that enables them to send alerts when they recognize problems (for example, when one or more User-determined thresholds are exceeded) Upon receiving these alerts, management entities are programmed to react by executing one, several, or a group of actions, including operator notification, Event logging, system shutdown, and automatic attempts at system repair. Management entities also can poll end stations to check the values of certain variables. Polling can be automatic or user-initiated, but agents in the managed devices respond to all polls. Agents are software modules that first compile information about the managed devices in which they reside, then store this information in a management database, and finally provide it (proactively or reactively) to management Entities within network management systems (NMSs) via network management protocol. Well-known network management protocols include the Simple Network Management Protocol (SNMP) and Common Management Information Protocol (CMIP). Management proxies are entities that provide management information on behalf of other entities. Figure 6-1 depicts typical network management architecture.

Performance ManagementThe goal of performance management is to measure and make available various aspects of network performance so that internetwork performance can be maintained at an acceptable level. Examples of Performance variables that might be provided include network throughput, user response times, and line utilization. Performance management involves three main steps. First, performance data is gathered on variables of interest to network administrators. Second, the data is analyzed to determine normal (baseline) levels. Finally, appropriate performance thresholds are determined for each important variable so that exceeding these thresholds indicates a network problem worthy of attention. Management entities continually monitor performance variables. When a performance threshold is exceeded, an alert is generated and sent to the network management system. Each of the steps just described is part of the process to set up a reactive system. When performance becomes unacceptable because of an exceeded user-defined threshold, the system reacts by sending a Message. Performance management also permits proactive methods: For example, network simulation can be used to project how network growth will affect performance metrics. Such simulation can alert administrators to impending problems so that counteractive measures can be taken.Configuration ManagementThe goal of configuration management is to monitor network and system configuration information so that the effects on network operation of various versions of hardware and software elements can be tracked and managed. Each network device has a variety of version information associated with it. An engineering workstation, for example, may be configured as follows: Operating system, Version 3.2 Ethernet interface, Version 5.4 TCP/IP software, Version 2.0 NetWare software, Version 4.1 NFS software, Version 5.1 Serial communications controller, Version 1.1 X.25 software, Version 1.0 SNMP software, Version 3.1Configuration management subsystems store this information in a database for easy access. When a problem occurs, this database can be searched for clues that may help solve the problem.Accounting ManagementThe goal of accounting management is to measure network utilization parameters so that individual or group uses on the network can be regulated appropriately. Such regulation minimizes network problems (because network resources can be apportioned based on resource capacities) and maximizes the fairness of network access across all users. As with performance management, the first step toward appropriate accounting management is to measure utilization of all important network resources. Analysis of the results provides insight into current usage patterns, and usage quotas can be set at this point. Some correction, of course, will be required to reach optimal access practices. From this point, ongoing measurement of resource use can yield billing information as well as information used to assess continued fair and optimal resource utilization.Fault ManagementThe goal of fault management is to detect, log, notify users of, and (to the extent possible) automatically fix network problems to keep the network running effectively. Because faults can cause downtime or unacceptable network degradation, fault management is perhaps the most widely implemented of the ISO network management elements. Fault management involves first determining symptoms and isolating the problem. Then the problem is fixed and the solution is tested on all-important subsystems. Finally, the detection and resolution of the problem is recorded.

Security ManagementThe goal of security management is to control access to network resources according to local guidelines so that the network cannot be sabotaged (intentionally or unintentionally) and sensitive information cannot be accessed by those without appropriate authorization. A security management subsystem, for example, can monitor users logging on to a network resource and can refuse access to those who enter inappropriate access codes. Security management subsystems work by partitioning network resources into authorized and unauthorized areas. For some users, access to any network resource is inappropriate, mostly because such users are usually company outsiders. For other (internal) network users, access to information originating from a particular department is inappropriate. Access to Human Resource files, for example, is inappropriate for most users outside the Human Resources department. Security management subsystems perform several functions. They identify sensitive network resources (including systems, files, and other entities) and determine mappings between sensitive network resources and user sets. They also monitor access points to sensitive network resources and log inappropriate access to sensitive network resources.Internet Protocol (IP)The Internet Protocol (IP) is a network-layer (Layer 3) protocol that contains addressing information and some control information that enables packets to be routed. IP is documented in RFC 791 and is the primary network-layer protocol in the Internet protocol suite. Along with the Transmission Control Protocol (TCP), IP represents the heart of the Internet protocols. IP has two primary responsibilities: providing connectionless, best-effort delivery of datagrams through an internetwork; and providing fragmentation and reassembly of datagrams to support data links with different maximum-transmission unit (MTU) sizes.The following discussion describes the IP packet fields. Versionindicates the version of IP currently used. IP Header Length (IHL)indicates the datagram header length in 32-bit words. Type-of-ServiceSpecifies how an upper-layer protocol would like a current datagram to be handled, and assigns datagram various levels of importance. Total Lengthspecifies the length, in bytes, of the entire IP packet, including the data and header. Identificationcontains an integer that identifies the current datagram. This field is used to help piece together datagram fragments. Flagsconsist of a 3-bit field of which the two low-order (least-significant) bits control fragmentation. The low-order bit specifies whether the packet can be fragmented. The middle bit specifies whether the packet is the last fragment in a series of fragmented packets. The third orHigh-order bit is not used. Fragment Offsetindicates the position of the fragments data relative to the beginning of the data in the original datagram, which allows the destination IP process to properly reconstruct the original datagram. Time-to-Livemaintains a counter that gradually decrements down to zero, at which point the datagram is discarded. This keeps packets from looping endlessly. ProtocolIndicates which upper-layer protocol receives incoming packets after IP processing is complete. Header Checksumhelps ensure IP header integrity. Source Addressspecifies the sending node. Destination Addressspecifies the receiving node. OptionsAllows IP to support various options, such as security. DataContains upper-layer information.IP AddressingAs with any other network-layer protocol, the IP addressing scheme is integral to the process of routing IP datagram through an internetwork. Each IP address has specific components and follows a basic format. These IP addresses can be subdivided and used to create addresses for sub networks, as discussed in more detail later in this chapter. Each host on a TCP/IP network is assigned a unique 32-bit logical address that is divided into two main parts: the network number and the host number. The network number identifies a network and must be assigned by the Internet Network Information Center (InterNIC) if the network is to be part of the Internet. An Internet Service Provider (ISP) can obtain blocks of network addresses from the InterNIC and can itself assign address space as necessary. The host number identifies a host on a network and is assigned by the local network administrator

IP Address FormatThe 32-bit IP address is grouped eight bits at a time, separated by dots, and represented in decimal format (known as dotted decimal notation). Each bit in the octet has a binary weight (128, 64, 32,16, 8, 4, 2, 1). The minimum value for an octet is 0, and the maximum value for an octet is 255.

IP Address ClassesIP addressing supports five different address classes: A, B,C, D, and E. Only classes A, B, and C are available for commercial use. The left-most (high-order) bits indicate the network class. Table 30-1 provides reference information about the five IP address classes.

IP Subnet AddressingIP networks can be divided into smaller networks called subnetworks (or subnets). Subnetting provides the network administrator with several benefits, including extra flexibility, more efficient use of network addresses, and the capability to contain broadcast traffic (a broadcast will not cross a router). Subnets are under local administration. As such, the outside world sees an organization as a single network and has no detailed knowledge of the organizations internal structure. A given network address can be broken up into many subnetworks. For example, 172.16.1.0, 172.16.2.0, 172.16.3.0, and 172.16.4.0 are all subnets within network 171.16.0.0. (All 0s in the host portion of an address specifies the entire network.)IP Subnet MaskA subnet address is created by borrowing bits from the host field and designating them as the subnet field. The number of borrowed bits varies and is specified by the subnet mask. Subnet masks use the same format and representation technique as IP addresses. The subnet mask, however, has binary 1s in all bits specifying the network and subnetwork fields, and binary 0s in all bits specifying the host field. Subnet mask bits should come from the high-order (left-most) bits of the host field, illustrates. Details of Class B and C subnet mask types follow. Class A addresses are not discussed in this chapter because they generally are subnetted on an 8-bit boundary. Various types of subnet masks exist for Class B and C subnets. The default subnet mask for a Class B address that has no subnetting is 255.255.0.0, while the subnet mask for a Class B address 171.16.0.0 that specifies eight bits of subnetting is 255.255.255.0. The reason for this is that eight bits of subnetting or 28 2 (1 for the network address and 1 for the broadcast address) = 254 subnets possible, with 28 2 = 254 hosts per subnet. The subnet mask for a Class C address 192.168.2.0 that specifies five bits of subnetting is 255.255.255.248.With five bits available for subnetting, 25 2 = 30 subnets possible, with 23 2 = 6 hosts per subnet. The reference charts shown in table 302 and table 303 can be used when planning Class B and C networks to determine the required number of subnets and hosts, and the appropriate subnet mask.

How Subnet Masks are Used to Determine the Network NumberThe router performs a set process to determine the network (or more specifically, the subnetwork) address. First, the router extracts the IP destination address from the incoming packet and retrieves the internal subnet mask. It then performs a logical AND operation to obtain the network number. This causes the host portion of the IP destination address to be removed, while the destination network number remains. The router then looks up the destination network number and matches it with an outgoing interface. Finally, it forwards the frame to the destination IP address. Specifics regarding the logical AND operation are discussed in the following section. Logical AND Operation Three basic rules govern logically ANDing two binary numbers. First, 1 ANDed with 1 yield 1. Second, 1 ANDed with 0 yields 0. Finally, 0 ANDed with 0 yields 0. The truth table provided in table 304 illustrates the rules for logical AND operations

Two simple guidelines exist for remembering logical AND operations: Logically ANDing a 1 with a 1 yields the original value, and logically ANDing a 0 with any number yields 0. Figure 30-9 illustrates that when a logical AND of the destination IP address and the subnet mask is performed, the subnetwork number remains, which the router uses to forward the packet.INTERNET ROUTINGInternet routing devices traditionally have been called gateways. In todays terminology, however, the term gateway refers specifically to a device that performs application-layer protocol translation between devices. Interior gateways refer to devices that perform these protocol functions between machines or networks under the same administrative control or authority, such as a corporations internal network. These are known as autonomous systems. Exterior gateways perform protocol functions between independent networks. Routers within the Internet are organized hierarchically. Routers used for information exchange within autonomous systems are called interior routers, which use a variety of Interior Gateway Protocols (IGPs) to accomplish this purpose. The Routing Information Protocol (RIP) is an example of an IGP. Routers that move information between autonomous systems are called exterior routers. These routers use an exterior gateway protocol to exchange information between autonomous systems. The Border Gateway Protocol (BGP) is an example of an exterior gateway protocol.IP RoutingIP routing protocols are dynamic. Dynamic routing calls for routes to be calculated automatically at regular intervals by software in routing devices. This contrasts with static routing, where routers are established by the network administrator and do not change until the network administrator changes them. An IP routing table, which consists of destination address/next hop pairs, is used to enable dynamic routing. An entry in this table, for example, would be interpreted as follows: to get to network172.31.0.0, send the packet out Ethernet interface 0 (E0).IP routing specifies that IP datagrams travel through internetworks one hop at a time. The entire route is not known at the onset of the journey, however. Instead, at each stop, the next destination is calculated by matching the destination address within the datagram with an entry in the current nodes routing table. Each nodes involvement in the routing process is limited to forwarding packets based on internal information. The nodes do not monitor whether the packets get to their final destination, nor does IP provide for error reporting back to the source when routing anomalies occur. This task is left to another Internet protocol, the Internet Control-Message Protocol (ICMP).

Enhanced Interior Gateway Routing ProtocolThe Enhanced Interior Gateway Routing Protocol (EIGRP) represents an evolution from its predecessor IGRP (Interior Gateway Routing Protocol). This evolution resulted from changes in networking and the demands of diverse, large-scale internetworks. EIGRP integrates the capabilities of link-state protocols into distance vector protocols. Additionally, EIGRP contains several important protocols that greatly increase its operational efficiency relative to other routing protocols. One of these protocols is the Diffusing update algorithm (DUAL) developed at SRI International by Dr. J.J. Garcia-Luna-Aceves. DUAL enables EIGRP routers to determine whether a path advertised by a neighbor is looped or loop-free, and allows a router running EIGRP to find alternate paths without waiting on updates from other routers. EIGRP provides compatibility and seamless interoperation with IGRP routers. An automatic-redistribution mechanism allows IGRP routes to be imported into EIGRP, and vice versa, so it is possible to add EIGRP gradually into an existing IGRP network. Because the metrics for both protocols are directly translatable, they are as easily comparable as if they were routes that originated in their own autonomous systems (ASs). In addition, EIGRP treats IGRP routes as external routes and provides a way for the network administrator to customize them. This chapter provides an overview of the basic operations and protocol characteristics of EIGRP.EIGRP Capabilities and AttributesKey capabilities that distinguish EIGRP from other routing protocols include fast convergence, support for variable-length subnet mask, support for partial updates, and support for multiple network layer protocols. A router running EIGRP stores all its neighbors routing tables so that it can quickly adapt to alternate routes. If no appropriate route exists, EIGRP queries its neighbors to discover an alternate route. These queries propagate until an alternate route is found. Its support for variable-length subnet masks permits routes to be automatically summarized on a network number boundary. In addition, EIGRP can be configured to summarize on any bit boundary at any interface. EIGRP does not make periodic updates. Instead, it sends partial updates only when the metric for a route changes. Propagation of partial updates is automatically bounded so that only those routers that need the information are updated. As a result of these two capabilities, EIGRP consumes significantly less bandwidth than IGRP. EIGRP includes support for AppleTalk, IP, and Novell NetWare. The AppleTalk implementation redistributes routes learned from the Routing Table Maintenance Protocol (RTMP). The IP implementation redistributes routes learned from OSPF, Routing Information Protocol (RIP), Intermediate System-to-Intermediate System (IS-IS), Exterior Gateway Protocol (EGP), or Border Gateway Protocol (BGP). The Novell implementation redistributes routes learned from Novell RIP or Service Advertisement Protocol (SAP).Routing ConceptsEIGRP relies on four fundamental concepts: neighbor tables, topology tables, route states, and route tagging. Each of these is summarized in the discussions that follow.Neighbor TablesWhen a router discovers a new neighbor, it records the neighbors address and interface as an entry in the neighbor table. One neighbor table exists for each protocol-dependent module. When a neighbor sends a hello packet, it advertises a hold time, which is the amount of time that a router treats a neighbor as reachable and operational. If a hello packet is not received within the hold time, the hold time expires and DUAL is informed of the topology change. The neighbor-table entry also includes information required by RTP. Sequence numbers are employed to match acknowledgments with data packets, and the last sequence number received from the neighbor is recorded so that out-of-order packets can be detected. A transmission list is used to queue packets for possible retransmission on a per-neighbor basis. Round-trip timers are kept in the neighbor-table entry to estimate an optimal retransmission interval.Topology TablesThe topology table contains all destinations advertised by neighboring routers. The protocol-dependent modules populate the table, and the table is acted on by the DUAL finite-state machine. Each entry in the topology table includes the destination address and a list of neighbors that have advertised the destination. For each neighbor, the entry records the advertised metric, which the neighbor stores in its routing table. An important rule that distance vector protocols must follow is that if the neighbor advertises this destination, it must use the route to forward packets. The metric that the router uses to reach the destination is also associated with the destination. The metric that the router uses in the routing table, and to advertise to other routers, is the sum of the best-advertised metric from all neighbors and the link cost to the best neighbor.Route StatesA topology-table entry for a destination can exist in one of two states: active or passive. A destination is in the passive state when the router is not performing a recomputation; it is in the active state when the router is performing a recomputation. If feasible successors are always available, a destination never has to go into the active state, thereby avoiding a recomputation. A recomputation occurs when a destination has no feasible successors. The router initiates the recomputation by sending a query packet to each of its neighboring routers. The neighboring router can send a reply packet, indicating that it has a feasible successor for the destination, or it can send a query packet, indicating that it is participating in the recomputation. While a destination is in the active state, a router cannot change the destinations routing-table information. After the router has received a reply from each neighboring router, the topology-table entry for the destination returns to the passive state, and the router can select a successor.Route TaggingEIGRP supports internal and external routes. Internal routes originate within an EIGRP AS. Therefore, a directly attached network that is configured to run EIGRP is considered an internal route and is propagated with this information throughout the EIGRP AS. External routes are learned by another routing protocol or reside in the routing table as static routes. These routes are tagged individually with the identity of their origin. External routes are tagged with the following information: Router ID of the EIGRP router that redistributed the route AS number of the destination Configurable administrator tag ID of the external protocol Metric from the external protocol Bit flags for default routingRoute tagging allows the network administrator to customize routing and maintain flexible policy controls. Route tagging is particularly useful in transit ASs, where EIGRP typically interacts with an interdomain routing protocol that implements more global policies, resulting in a very scalable, policy-based routing.Cisco IOS Modes of Operation The Cisco IOS software provides access to several different command modes. Each command mode provides a different group of related commands. For security purposes, the Cisco IOS software provides two levels of access to commands: user and privileged. The unprivileged user mode is called user EXEC mode. The privileged mode is called privileged EXEC mode and requires a password. The commands available in user EXEC mode are a subset of the commands available in privileged EXEC mode. The following table describes some of the most commonly used modes, how to enter the modes, and the resulting prompts. The prompt helps you identify which mode you are in and, therefore, which commands are available to you

User EXEC Mode: When you are connected to the router, you are started in user EXEC mode. The user EXEC commands are a subset of the privileged EXEC commands. Privileged EXEC Mode: Privileged commands include the following: Configure Changes the software configuration. Debug Display process and hardware event messages. Setup Enter configuration information at the prompts. Enter the command disable to exit from the privileged EXEC mode and return to user EXEC mode. Configuration Mode Configuration mode has a set of submodes that you use for modifying interface settings, routing protocol settings, line settings, and so forth. Use caution with configuration mode because all changes you enter take effect immediately. To enter configuration mode, enter the command configure terminal and exit by pressing Ctrl-Z.

Note: Almost every configuration command also has a no form. In general, use the no form to disable a feature or function. Use the command without the keyword no to re-enable a disabled feature or to enable a feature that is disabled by default. For example, IP routing is enabled by default. To disable IP routing, enter the no ip routing command and enter ip routing to re-enable it.Getting Help In any command mode, you can get a list of available commands by entering a question mark (?). Router>?To obtain a list of commands that begin with a particular character sequence, type in those characters followed immediately by the question mark (?). Router#co?Configure connect copy To list keywords or arguments, enter a question mark in place of a keyword or argument. Include a space before the question mark. Router# configure ?Memory Configure from NV memory network Configure from a TFTP network host terminal Configure from the terminal you can also abbreviate commands and keywords by entering just enough characters to make the command unique from other commands. For example, you can abbreviate the show command to sh.Configuration Files Any time you make changes to the router configuration, you must save the changes to memory because if you do not they will be lost if there is a system reload or power outage. There are two types of configuration files: the running (current operating) configuration and the startup configuration. Use the following privileged mode commands to work with configuration files. configure terminal modify the running configuration manually from the terminal. show running-config display the running configuration. show startup-config display the startup configuration. copy running-config startup-config copy the running configuration to the startup configuration. copy startup-config running-config copy the startup configuration to the running configuration. erase startup-config erase the startup-configuration in NVRAM. copy tftp running-config load a configuration file stored on a Trivial File Transfer Protocol (TFTP) server into the running configuration. copy running-configtftp store the running configuration on a TFTP server. IP Address Configuration Take the following steps to configure the IP address of an interface. Step 1: Enter privileged EXEC mode: Router>enable password Step 2: Enter the configure terminal command to enter global configuration mode. Router#config terminal Step 3: Enter the interface type slot/port (for Cisco 7000 series) or interface type port (for Cisco 2500 series) to enter the interface configuration mode. Example: Router (config)#interface ethernet 0/1 Step 4: Enter the IP address and subnet mask of the interface using the ip address ip address subnet mask command. Example, Router (config-if)#ip address 192.168.10.1 255.255.255.0 Step 5: Exit the configuration mode by pressing Ctrl-Z Router(config-if)#[Ctrl-Z]

Routing Protocol Configuration

EIGRP Step 1: Enter privileged EXEC mode: Router>enable password Step 2: Enter the configure terminal command to enter global configuration mode. Router#config terminal Step 3: Enter the router eigrp command Router(config)#router eigrp Step 4: Add the network number to use RIP and repeat this step for all the numbers. Router(config-router)#network network-number Example: Router(config-router)#network 192.168.10.0

Securing router with passwordSetting PasswordsThere are five passwords youll need to secure your Cisco routers: console, auxiliary, telnet (VTY), enable password, and enable secret. The enable secret and enable password are the ones used to set the password for securing privileged mode. Once the enable commands are set, users will be prompted for a password. The other three are used to configure a password when user mode is accessed through the console port, through the auxiliary port, or via Telnet.Lets take a look at each of these now.Enable PasswordsYou set the enable passwords from glob