Bài giảng Network+ Certification - Chapter 17, Network Troubleshooting Procedures

Tài liệu Bài giảng Network+ Certification - Chapter 17, Network Troubleshooting Procedures: Chapter 17, Network Troubleshooting Procedures |1| Chapter Overview A. Identifying Network Components B. Troubleshooting a Network Chapter 17, Lesson 1 Identifying Network Components 1. Introduction A. Network technicians often have to troubleshoot problems on unfamiliar networks. B. When you work on an unfamiliar network installation, you should first determine the network’s basic hardware configuration. 1. You often must approach a problem without having any information about the network infrastructure and the equipment used to build it. a. In a perfect world, you would have access to schematic diagrams of the cabling and an inventory of the network hardware, but this rarely happens. C. Usually, you must examine the equipment yourself to find out what you need to know. 2. Recognizing Computer Ports A. Computers have many different ports. B. Most of the ports on computers manufactured today are labeled, but you might come across uni...

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Chapter 17, Network Troubleshooting Procedures |1| Chapter Overview A. Identifying Network Components B. Troubleshooting a Network Chapter 17, Lesson 1 Identifying Network Components 1. Introduction A. Network technicians often have to troubleshoot problems on unfamiliar networks. B. When you work on an unfamiliar network installation, you should first determine the network’s basic hardware configuration. 1. You often must approach a problem without having any information about the network infrastructure and the equipment used to build it. a. In a perfect world, you would have access to schematic diagrams of the cabling and an inventory of the network hardware, but this rarely happens. C. Usually, you must examine the equipment yourself to find out what you need to know. 2. Recognizing Computer Ports A. Computers have many different ports. B. Most of the ports on computers manufactured today are labeled, but you might come across units that have no markings. 1. When ports are unlabeled, you must be able to discern their functions. |2| C. The ports on a typical computer are located either on the motherboard or on expansion cards that plug into the system bus. 1. If the same type of port can have more than one function, you can sometimes tell what a port does by where it is located. 2. The locations of the motherboard ports vary, depending on the design of the computer. |3| 3. An older computer might have the motherboard ports grouped in a separate area away from the motherboard itself. a. On an older computer, the motherboard ports are separate modules that are bolted to the back of the computer case and connected to the motherboard with cables. b. The expansion slots are grouped in a different area, where the ports provided by the expansion cards installed in the system are located. |4| 4. A newer computer might have all of the motherboard ports lined up in a row. a. On a newer computer, the ports are part of the motherboard. (1) The ports run horizontally along the bottom of the computer. (2) All ports are located on the motherboard, including the video port, which is typically provided by an expansion card. 2 Outline, Chapter 17 Network+ Certification, Second Edition D. Serial ports 1. Modems nearly always use serial ports. a. A few proprietary networking systems use standard unshielded twisted-pair (UTP) cable that plugs into an adapter connected to a serial port. |5| 2. Computers manufactured today typically have two serial ports on the motherboard, both of which use male DB-9 connectors. 3. Older computers may also use DB-25 connectors for serial ports. |6| a. The typical configuration used to be one DB-9 connector and one DB-25 connector. 4. Because nine pins more than satisfy the requirements for serial communications, a computer can use either a DB-9 or a DB-25 connector. 5. Serial connections can run at speeds from 110 to 115,200 bits per second (bps). 6. D-type connectors are not used exclusively for serial ports. a. Parallel ports also use DB-25 connectors (although they are female instead of male). b. In rare cases, Small Computer System Interface (SCSI) adapters use DB-25 connectors. c. DB-9 connectors were at one time used as video ports for connections to monitors, although they were female instead of male. d. Do not confuse the various functions of DB-9 and DB-25 connectors; they are not interchangeable. E. Parallel ports 1. Parallel ports were designed for use by printers. a. In recent years, parallel ports have been enhanced to provide more efficient bidirectional communications between the computer and the attached device. |7| 2. Parallel ports always use a female DB-25 connector. 3. The average computer today has one parallel port. 4. A select group of SCSI devices can also be plugged into a computer’s parallel port. a. These devices use the same basic principles of communication as standard SCSI devices, but they use a different interface to the computer. b. The parallel port interface is slower than that of a dedicated SCSI host adapter. c. For many users, the ability to move a SCSI device from computer to computer without installing an adapter card is worth the sacrifice in speed. 5. Although nearly all computers today have two serial ports and one parallel port, you can use an input/output (I/O) expansion card to add ports. a. It is rarely necessary to add more serial and parallel ports because (1) The universal serial bus (USB) has increased in popularity Outline, Chapter 17 3 Network+ Certification, Second Edition (2) The Industry Standard Architecture (ISA) slots that most of the I/O cards plug into have gradually been eliminated F. Video ports |8| 1. The video connector on computers today uses a female 15-pin D-shell connector with three rows of five pins each. 2. Before the introduction of the VGA standard in 1987, computers used digital monitors that connected to a female DB-9 port in the video adapter. G. Keyboard and mouse ports |9| 1. On today’s computers, keyboards and mice (or other pointing devices) use the same type of port, which has a round, female, six-pin connector called a mini-DIN. a. DIN stands for Deutsche Industrie Norm, the name of the German organization that developed the standard for the connector. b. Also known as a PS/2 connector, which comes from the name of the IBM computer model that first used it c. Mini-DIN connectors on computers are usually labeled with pictograms that indicate which connector is for the keyboard and which connector is for the mouse. d. Accidentally cross-connecting the keyboard and the mouse does not damage the hardware, but the two ports are not interchangeable. |10| 2. Before the mini-DIN connector became standard equipment, keyboards used a larger, female five-pin DIN connector. a. In a few cases, computers and other peripherals use the older five-pin DIN connector to carry power from a transformer to the device. b. Plugging a power connector into a keyboard port can severely damage a computer. (1) Because few computers today use the five-pin DIN keyboard connector, the danger of this happening is remote. 3. Mice and other pointing devices used either DB-9 serial ports or a port on a dedicated bus mouse card. |11| H. Universal serial bus ports 1. The USB is a relatively recent innovation that is rapidly replacing many of the ports commonly included on computers, such as the serial, parallel, keyboard, and mouse ports. 2. The USB is a multipurpose bus that a. Runs at up to 12 Mbps b. Supports a wide range of devices, from keyboards and mice to cameras and disk drives, all through the same interface 3. Computers today typically have two USB ports, which use rectangular, female, four-conductor connectors. |12| a. USB ports are not like any other port in the computer. 4. USB devices have B-connectors, which are more square-shaped than A-connectors. |13| I. Small Computer System Interface ports 4 Outline, Chapter 17 Network+ Certification, Second Edition 1. SCSI is a mass storage interface that supports many different internal and external devices at speeds up to 160 Mbps. a. Network servers often use SCSI for internal hard drives and other storage media, but they can also have external SCSI connections. b. Since SCSI’s inception in the early 1980s, the interface has undergone several revisions to increase its speed and capabilities. c. These revisions have necessitated the use of different cables and connectors. 2. SCSI implementations typically involve a host adapter card that plugs into the computer’s expansion bus. a. A few computers have a SCSI adapter integrated into the motherboard. 3. A SCSI host adapter usually has both internal and external connectors. a. Internally, SCSI uses ribbon connectors that attach to hard drives and other devices. b. External SCSI cables are thick and relatively inflexible because of their heavy shielding and the tight bundling of wires contained inside. |14| 4. SCSI connectors a. The earliest SCSI implementations used a 50-pin Centronics connector for external connections. (1) Identical in design to the Centronics connector used on most printers, except the 50-pin connector is larger (2) The SCSI bus was 8 bits wide and ran at 5 Mbps. (3) The 8-bit/5-Mbps SCSI interface also used a standard DB-25 connector, such as on early IBM, Apple Macintosh, and Sun Microsystems computers. b. Newer SCSI implementations use unique 50-pin high-density or 68-pin high-density connectors on their cables. (1) These connectors have two rows containing equal numbers of pins that are smaller than those in a DB-25 connector. (2) The 50-pin version has clips on the connector; the 68-pin version has thumbscrews. (3) The 50-pin connectors are used primarily on Fast SCSI implementations running at 10 Mbps. (4) The 68-pin connector is used for Fast/Wide SCSI running at 20 Mbps. c. Another type of SCSI used by some drives today is the Single Connector Attachment (SCA) SCSI, which uses a special 80-pin connector that supplies both the power and the data connections to the drive. (1) The SCA connector is similar in appearance to a Centronics connector, although it is a bit wider. J. Network cable connectors 1. Network interface cards (NICs) can often have several different types of connectors on them. a. You can use only one connector at a time. Outline, Chapter 17 5 Network+ Certification, Second Edition b. This type of adapter is called a combination NIC, or combo NIC. c. Additional connectors often add substantially to the cost of the NIC. 2. The type of connector you use should depend on the data-link layer protocol and the type of cable your network uses. |15| 3. Ethernet NICs often include three network connectors: an Attachment Unit Interface (AUI) connector, a bayonet-Neill-Concelman (BNC) connector, and an RJ-45 connector. a. AUI connector (1) Oldest of the Ethernet cable connectors (2) 15-pin female D-shell connector with two rows of pins (3) Used to attach an AUI cable to the NIC in a computer; the other end of the AUI cable connects to a thick Ethernet network. (4) Ethernet NICs with an AUI connector (in addition to others) are still common, but the connector is rarely used. b. BNC connector (1) Connects a computer to a thin Ethernet network. |16| (2) You can attach a special T fitting to the connector on the NIC, and then attach the Ethernet cables to the arms of the T, which allows you to run the cable from computer to computer, forming a bus topology. c. RJ-45 connector (1) Used on most Ethernet networks installed today |17| (2) Most Ethernet networks today use UTP cable, so it is most economical to buy NICs with just a single RJ-45 connector. (3) RJ-45 connectors look like telephone jacks, except that the RJ-45 has eight contacts and the RJ-11 telephone connector has four (or sometimes six) contacts. (4) An RJ-11 plug is slightly narrower than an RJ-45, but it is easy to mistake one for the other. (5) You can insert an RJ-11 plug into an RJ-45 jack, but you cannot plug an RJ-45 plug into an RJ-11 jack. (6) Plugging a telephone cable into a NIC’s RJ-45 connector will not cause any damage, but network communication will not take place. (7) Plugging a standard analog modem into a digital telephone jack connected to a switchboard can ruin the modem. (8) Usually, the easiest way to tell modem connectors from NIC connectors on an installed expansion card is by the number of connectors. (9) Most modems have two RJ-11 connectors, one for the connection to the telephone line and one for a telephone, but NICs only have one RJ-45 connector. 4. Token Ring connectors a. Token Ring networks can use UTP cables, just like Ethernet, so the connector you see on the NIC is the same female RJ-45. 6 Outline, Chapter 17 Network+ Certification, Second Edition b. Token Ring networks that use IBM Type 1 cabling have female DB-9 connectors on their NICs. (1) A Type 1 Token Ring cable uses a male DB-9 connector on one end to connect to the NIC, and an IBM data connector (IDC) on the other end to connect to the multistation access unit (MAU). |18| c. Token Ring media filters (1) If you want to avoid the expense of the Type 1 cabling, you can use devices called Token Ring media filters to connect Type 1 NICs to a UTP network. (2) The media filter is essentially an adapter with a male DB-9 connector and a female RJ-45 connector on it. (3) You plug the DB-9 connector into the NIC and connect a standard UTP network cable to the RJ-45 connector. 3. Recognizing Network Components A. Network interface adapters 1. Network interface adapters (or NICs) look like other types of expansion cards. 2. NICs are made for each of the common bus types. a. The bus types most commonly used by NICs today are Peripheral Component Interconnect (PCI) and ISA. 3. The best way to distinguish a NIC from another type of card is by looking at the connectors. 4. Motherboard-resident network interface adapters do not require a bus slot, and the electronics can easily be lost in the maze of motherboard circuitry. a. An RJ-45 jack on the back of the computer indicates support for UTP Ethernet. |19| B. Hubs and switches |20| 1. A hub can be either a stand-alone box or a unit that mounts into a standard 19-inch-wide rack used for large network installations. 2. Hubs might be called by different names (a Token Ring hub is called a MAU, for example) and use different types of connectors, but their general appearance is the same. 3. Hubs can support any one of several data-link layer protocols, including Ethernet, Fiber Distributed Data Interface (FDDI), and Token Ring. 4. A hub can have as few as 4 ports or as many as 24. a. On an externally wired network segment, a single cable connects the network interface adapter in each computer to a hub port. b. On an internally wired network segment, each hub port is connected to a patch panel port using a short patch cable. (1) The patch panel is connected to all of the cable runs inside the building’s walls and ceilings, terminating at wall plates throughout the installation. (2) Another patch cable connects each wall plate to a computer. Outline, Chapter 17 7 Network+ Certification, Second Edition 5. The basic identifying feature of a hub is one or more rows of female connectors. a. Some hubs use connectors other than RJ-45. (1) Straight-tip fiber optic connectors, which are bayonet-style connectors (2) Type 1 Token Ring connectors (3) IBM data connectors |21| 6. In most cases, a hub has rows of light-emitting diode (LED) lamps that correspond to the network cable ports. a. The LEDs are activated by the link pulse signals generated by network interface adapters when they are active and functioning properly. b. An LED that is not lit indicates one of the following problems: (1) A malfunction in the hub or the network interface adapter (2) A broken or disconnected cable (3) A computer that is turned off or missing |22| 7. Switches a. Look like hubs (1) Switches and hubs made by the same manufacturer can look identical, except for their markings. b. The difference between a hub and a switch is in the internal manipulation of incoming data. (1) A hub forwards incoming traffic out through all the other ports, but a switch forwards traffic only to the device for which it is destined. c. Switches are available in most of the same configurations as hubs, ranging from small units intended for home or small business networks to large rack-mounted devices. d. Some switches include an additional nine-pin serial port that is used to connect the device to a computer with a null modem cable. (1) This interface allows you to perform the initial configuration of the unit before it is connected to the network. (2) After the initial configuration is complete, you can access the switch’s management functions by using a Telnet session from a computer on the network. |23| C. Patch panels 1. Also called punchdown blocks 2. Typically mounted either on a wall or in a rack; not stand-alone units 3. Have rows of female RJ-45 jacks or other connectors, just like hubs 4. Only function is to provide connections between internal cable installations and patch cables 5. Some patch panels are modular, consisting of a framework and interchangeable connectors. |24| D. Bridges and routers 1. Bridges and routers can be stand-alone or rack-mounted units. 8 Outline, Chapter 17 Network+ Certification, Second Edition 2. Because bridges and routers only connect two network segments together, they do not have as many ports as hubs do and are often more difficult to recognize. a. A stand-alone bridge or router can take the form of any type of device that contains two or more ports. b. Bridges and routers sometimes have LED lamps for status displays. 3. Bridges and routers can connect local area networks (LANs) of the same type or different types. a. A bridge or router used to connect two internal network segments can have two ports of the same type, such as two RJ-45 jacks, or two different ports, which connect to different types of networks. b. In most cases, bridges used internally are transparent bridges, which connect the same type of network, so they have two identical ports. c. A device with two different ports, such as an RJ-45 jack and a BNC connector, is more likely to be a router. d. Routers can also have two identical ports, either because (1) They connect two LANs of the same type, or (2) They connect two different types of LANs that use the same cable, such as 10Base-T and UTP Token Ring 4. Bridges and routers can also connect a LAN to a remote network by using a leased telephone line or other wide area network (WAN) connection. a. For a router connected to a WAN link, the identifying element of the unit is a serial port that is connected to a channel service unit/data service unit (CSU/DSU). b. The CSU/DSU provides the interface to the leased line, much as a modem provides the interface to a standard telephone line, except that the CSU/DSU is a digital device. 5. In addition to the serial port, the bridge or router also a. Has one or more ports for connecting to the LAN b. Uses any of the standard cable connectors, such as female RJ-45s |25| 6. Larger routers can be modular, consisting of a frame with multiple slots into which you plug separate modules supporting a specific type of network. E. Print servers 1. Devices that receive print jobs from clients on a network and feed them to the printer at the appropriate rate 2. The print server sometimes spools the print jobs. a. It stores them on a hard drive while waiting for the printer to be ready to receive them. 3. In some cases, a print server is a computer. a. You can connect a printer directly to a computer and share it with other users on the network. |26| 4. Stand-alone print servers can take two forms: a. Internal print server: an expansion card that you install in the printer itself Outline, Chapter 17 9 Network+ Certification, Second Edition b. External print server: a small device with one or more ports for connecting to the printer (or printers) and another for connecting to a network hub 5. The print server has an Internet Protocol (IP) address of its own, and computers on the network send their print jobs to the print server, which relays them to the appropriate printer. |27| F. Uninterruptible power supply devices 1. A UPS provides equipment with a temporary supply of electrical power in the event of an outage in the building’s main power supply. 2. A UPS is essentially a battery that is continuously charged when the main power is on. 3. You plug computers or other equipment into the UPS. a. If the power fails, the battery supplies power for a short time, long enough to safely turn off a computer without damaging its data. 4. UPS devices range from small units designed to protect a single computer to larger devices that can protect several computers at one time. a. Some large UPS devices can protect an entire data center or building. |28| 5. A UPS is a heavy box with a series of power outlets for equipment (typically on the back) and a standard electrical plug that connects to the building’s power source. a. Larger devices might require special power connections. 6. In many cases, a group of LEDs displays a. The amount of power left in the battery b. The load generated by the connected equipment 7. The best UPS units run connected devices off the battery at all times, while the battery is continuously charged. a. If the building power fails, the equipment continues to operate without interruption. 8. Lower-priced units run the equipment from the building’s power supply until it fails, and then they switch over to battery power. a. The brief interruption during the switchover can sometimes be enough to interrupt a disk writing process, causing data corruption. 9. High-quality units also have one or more serial ports that you can use to connect the UPS to a computer. a. A program or service running on the computer receives a signal from the UPS when building power fails. (1) After a specified interval the computer shuts itself down in a controlled fashion. (2) The UPS continues to protect against data loss, even when no one is present to shut down the computer. 10 Outline, Chapter 17 Network+ Certification, Second Edition Chapter 17, Lesson 2 Troubleshooting a Network 1. Introduction A. The key to troubleshooting is to have a plan of action. 1. Many of the trouble calls you will receive are likely to involve user issues such as the improper use of software. |29| B. When you are faced with a real problem, you should follow a set troubleshooting procedure, which should consist of the following steps: 1. Establish the symptoms. 2. Identify the affected area. 3. Establish what has changed. 4. Select the most probable cause. 5. Implement a solution. 6. Test the result. 7. Recognize the potential effects of the solution. 8. Document the solution. C. The steps you follow can be slightly different, or you can perform the steps in a slightly different order, but the overall process should be similar. |30| 2. Establishing the Symptoms A. The first step is to determine exactly what is going wrong and to note the effect of the problem on the network so that you can assign a priority to a problem. 1. In a large network environment, there are often many more calls for support than the network support staff can handle at one time. 2. It is essential to establish a system of priorities that dictate which calls get addressed first. 3. As in the emergency department of a hospital, the priorities should not necessarily be based on who is first in line. a. Most often, the severity of the problem determines who gets attention first. (1) However, it is usually not wise to ignore the political reality that problems of senior management are addressed before those of the rank and file. |31| B. Rules for establishing priorities 1. Shared resources take precedence over individual resources. a. A problem with a server or other network component that prevents many users from working must take precedence over one that affects only a single user. 2. Network-wide problems take precedence over workgroup or departmental problems. a. Resources that provide services to the entire network, such as e-mail servers, should take precedence over departmental resources, such as file and print servers. Outline, Chapter 17 11 Network+ Certification, Second Edition 3. Rate departmental issues according to the function of the department. a. Problems with resources belonging to a department that is critical to the organization, such as order entry or customer service call centers, should take precedence over departments that can better tolerate a period of down time, such as research and development. 4. System-wide problems take precedence over application problems. a. A problem that puts an entire computer out of commission, preventing a user from getting any work done, should take precedence over a problem a user is experiencing with a single device or application. C. Gathering information 1. It can be difficult to determine the exact nature of the problem from the user’s report. a. Narrowing down the cause of a problem involves obtaining accurate information about what has occurred. b. Users are often vague about what they were doing when they experienced the problem, or even what the indications of the problem were. (1) For example, users might call the help desk because they received an error message, but they neglect to write down the wording of the message. 2. Gentle training of users in the proper procedures for documenting and reporting problems is part of the network technician’s job. 3. Begin by asking questions like the following: a. What exactly were you doing when the problem occurred? b. Have you had any other problems? c. Was the computer behaving normally just before the problem occurred? d. Has any hardware or software been installed, removed, or reconfigured recently? e. Did you (or anyone else) do anything to try to resolve the problem? |32| 3. Identifying the Affected Area A. The next step is to see if the problem can be duplicated. 1. Network problems that you can easily duplicate are far easier to fix than those you cannot duplicate, primarily because you can easily test to see if your solution was successful. 2. However, many types of network problems are intermittent or occur for only a short time. a. In these cases, you might have to leave the incident open until the problem occurs again. B. Having the user reproduce the problem can sometimes lead to the solution. 1. User error is a common cause of problems that can seem to be hardware- or network-related to the inexperienced eye. 12 Outline, Chapter 17 Network+ Certification, Second Edition C. If the problem can be duplicated, you can start determining the actual source of the problem. 1. Example: if a user has trouble opening a file in a word processing application, the problem might be in the application, the user’s computer, the file server where the file is stored, or any of the networking components in between. D. The process of isolating the location of the problem consists of eliminating the elements that are not the cause, in a logical and methodical manner. E. If you can duplicate the problem, you can begin to isolate the cause by reproducing the conditions under which the problem occurred, using the following procedure: 1. Have the user reproduce the problem on the computer repeatedly, so that you can determine whether the user’s actions are triggering the error. 2. Sit at the computer yourself and perform the same task. a. If the problem does not occur, the cause might be in how the user is performing the task. (1) Check the user’s procedures carefully to see if he or she is doing something wrong. (2) You and the user might perform the same task in different ways, and the user’s method is exposing a problem that yours does not. 3. If the problem occurs when you perform the task, log off from the user’s account, log on using an account with administrative privileges, and repeat the task. a. If the problem does not occur, it is probably because the user does not have the rights or permissions needed to perform the task. 4. If the problem occurs, try to perform the same task on another, similarly equipped computer connected to the same network. a. If you cannot reproduce the problem on another computer, the cause lies in the user’s computer or its connection to the network. b. If the problem does occur on another computer, you are dealing with a network problem, either (1) In the server that the computer was communicating with, or (2) In the hardware that connects the computer and the server F. If you determine that the problem lies somewhere in the network and not in the user’s computer, you can then begin to isolate the area of the network that is the source of the problem. 1. If you can reproduce the problem on another nearby computer, you can then begin performing the same task on computers located elsewhere on the network. 2. You can try to reproduce the problem on another computer connected to the same hub, and then on a computer connected to a different hub on the same LAN. 3. If the problem occurs throughout the LAN, try a computer on a different LAN. Outline, Chapter 17 13 Network+ Certification, Second Edition 4. Eventually, you should be able to narrow down the source of the problem to a particular component, such as a server, router, hub, or cable. |33| 4. Establishing What Has Changed A. When a computer or other network component that used to work properly now does not work, some change has probably occurred. 1. When a user reports a problem, one of the most important pieces of information you can gather is how the computing environment changed immediately before the malfunction occurred. a. Unfortunately, getting this information from the user can often be difficult. 2. On a network with properly established maintenance and documentation procedures, it should be possible to determine if any upgrades or modifications to the user’s computer have been made recently. a. Look in official records for information like this. B. Major changes, such as the installation of new hardware or software, are obvious possible causes of the problem. 1. You must be conscious of causes evidenced in more subtle changes as well. a. Example: an increase in network traffic levels, as disclosed by a protocol analyzer, can contribute to a reduction in network performance. 2. If several users of the same application, cable segment, or LAN report occasional problems, there might be a fault in a network component. C. Tracking down the source of a networking problem can often be a form of detective work, and learning to “interrogate” your “suspects” properly can be an important part of the troubleshooting process. |34| 5. Selecting the Most Probable Cause A. An old medical school axiom says that when you hear hoofbeats, think horses, not zebras. 1. In the context of network troubleshooting, this means that when you look for possible causes of a problem, start with the obvious first. a. Example: if a workstation cannot communicate with a file server, do not start by checking the routers between the two systems. Check the simple things on the workstation first, such as whether the network cable is plugged into the computer. B. The other important part of the process is to work methodically and document everything you check so that you do not duplicate your efforts. |35| 6. Implementing a Solution A. After you have isolated the problem to a particular piece of equipment, you can try to determine if it is caused by hardware or software. 1. If it is a hardware problem, you might replace the faulty unit or use an alternate. 14 Outline, Chapter 17 Network+ Certification, Second Edition a. Example: if the problem is a communication problem, you might replace network cables until you find one that is faulty. b. Example: if the problem is in a server, you can replace components, such as hard drives, until you find the culprit. 2. If it is a software problem, you might try the following: a. Use a different computer to run the application or store the data. b. Reinstall the software on the offending system. 3. In some cases, the process of isolating the source of a problem can actually resolve the problem. a. Example: if you replace network patch cables until you find the one that is faulty, replacing the bad cable resolves the problem. 4. In other cases, the resolution might be more involved, such as reinstalling a server application or operating system. a. Because other users might need to access that server, you might have to wait to resolve the problem until later, when the network is not in use and after you have backed up the data stored on the server. b. In some cases, you might have to bring in outside help, such as a contractor to pull new cables. (1) Carefully schedule outside help to avoid having the contractor’s work conflict with users’ activities. c. Sometimes, you might want to provide an interim solution, such as a substitute workstation or server, until you can definitively resolve the problem. |36| 7. Testing the Results A. After you have resolved the problem, you should return to the beginning of the process and repeat the task that originally caused the problem. 1. If the problem no longer occurs, you should test the other functions related to the changes you made to ensure that fixing one problem has not created another. 2. The time you spent documenting the troubleshooting process becomes worthwhile at this point. 3. You should repeat the procedures you used to duplicate the problem exactly, to ensure that the problem the user originally experienced has been completely eliminated and is not just temporarily masked. a. If the problem was intermittent to begin with, it might take some time to ascertain if your solution has worked. b. You might need to check with the user several times to make sure that the problem has not recurred. 8. Recognizing the Potential Effects of the Solution A. It is important to keep an eye on the big network picture and not let yourself become too involved in the problems experienced by one user (or application or LAN). 1. While you implement a solution to one problem, it is possible to create another problem that is more severe or that affects more users. Outline, Chapter 17 15 Network+ Certification, Second Edition a. Example: if users on one LAN experience high traffic levels that diminish their workstation performance, you might be able to remedy the problem by connecting some of their computers to a different LAN. (1) However, although this solution might help the users originally experiencing the problem, you might overload another LAN in the process, causing another problem that is more severe than the first one. b. You might want to consider a more far-reaching solution instead, such as creating an entirely new LAN and moving some of the affected users over to it. |37| 9. Documenting the Solution A. Although it is presented here as a separate step, the process of documenting your actions should begin as soon as the user calls for help. B. A well-organized network support organization should use a system that registers each problem call as a trouble ticket that eventually contains 1. A complete record of the problem 2. The steps taken to isolate and resolve the problem C. A technical support organization often operates by using tiers, which are groups of technicians of different skill levels. 1. Calls come in to the first tier. a. If the problem is complex or the first-tier technician cannot resolve it, the call is escalated to the second tier, which is composed of senior technicians. 2. As long as everyone involved in the process documents his or her activities, there should be no problem when one technician hands off the trouble ticket to another. 3. Keeping careful notes prevents people from duplicating each other’s efforts. D. Finally, explain to the user what happened and why. 1. The average network user is probably not interested in hearing all the technical details, but it is a good idea to let users know whether their actions caused the problem, exacerbated it, or made it more difficult to resolve. 2. Educating users can lead to quicker resolutions or prevent a problem from occurring altogether. |38| Chapter Summary A. Identifying network components 1. Computers have a variety of ports, some of which are implemented by the motherboard and others by expansion cards. 2. Computers use many different types of connectors for their various interfaces. 16 Outline, Chapter 17 Network+ Certification, Second Edition a. In some cases the same connector type can provide different functions. 3. SCSI host adapters can use any one of several types of connectors, which are not interchangeable. B. Troubleshooting a network 1. The network troubleshooting procedure involves several steps, including identifying, duplicating, isolating, resolving, and documenting the problem. 2. Isolating a network problem is a matter of eliminating hardware and software components as possible causes. 3. Maintaining careful documentation and methodically following a troubleshooting procedure are essential parts of maintaining a network.

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