Belajar Troubleshooting

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    Network Troubleshooting Overview

    These sections introduce you to the concepts and practice of network troubleshooting :

    Introduction to Network Troubleshooting Network Troubleshooting Framework Troubleshooting Strategy

    Network troubleshooting means recognizing and diagnosingnetworking problems with the goal of keeping your network runningoptimally. As a network administrator, your primary concern ismaintaining connectivity of all devices (a process often called fault management ). You also continually evaluate and improve yournetwork's performance . Because serious networking problems cansometimes begin as performance problems, paying attention toperformance can help you address issues before they become serious.

    About Connectivity Problems

    Connectivity problems occur when end stations cannot communicatewith other areas of your local area network (LAN) or wide areanetwork (WAN). Using management tools, you can often fix aconnectivity problem before users even notice it. Connectivityproblems include:

    Loss of connectivity - When users cannot access areas of yournetwork , your organization's effectiveness is impaired.Immediately correct any connectivity breaks.

    Intermittent connectivity - Although users have access to network resourcessome of the time, they are still facing periods of downtime. Intermittentconnectivity problems can indicate that your network is on the verge of a major

    break. If connectivity is erratic, investigate the problem immediately. Timeout problems - Timeouts cause loss of connectivity, but are often associated

    with poor network performance.

    About Performance Problems

    Your network has performance problems when it is not operating aseffectively as it should. For example, response times may be slow, thenetwork may not be as reliable as usual, and users may becomplaining that it takes them longer to do their work. Someperformance problems are intermittent, such as instances of duplicateaddresses. Other problems can indicate a growing strain on yournetwork , such as consistently high utilization rates.

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    If you regularly examine your network for performance problems, youcan extend the usefulness of your existing network configuration andplan network enhancements, instead of waiting for a performanceproblem to adversely affect the users' productivity.

    Solving Connectivity and Performance ProblemsWhen you troubleshoot your network , you employ tools andknowledge already at your disposal. With an in-depth understanding of your network , you can use network software tools, such as "Ping" ,and network devices, such as "Analyzers" , to locate problems, andthen make corrections, such as swapping equipment or reconfiguringsegments, based on your analysis.

    Transcend provides another set of tools for network troubleshooting . These tools have graphical user interfaces thatmake managing and troubleshooting your network easier. With

    "Transcend Applications" , you can:

    Baseline your network's normal status to use as a basis forcomparison when the network operates abnormally

    Precisely monitor network events Be notified immediately of critical problems on your network , such as a device

    losing connectivity Establish alert thresholds to warn you of potential problems that you can correct

    before they affect your network Resolve problems by disabling ports or reconfiguring devices

    See "Your Network Troubleshooting Toolbox" for details about eachtroubleshooting tool.

    Network Troubleshooting Framework

    The International Standards Organization (ISO) Open SystemsInterconnect (OSI) reference model is the foundation of all network communications. This seven-layer structure provides a clear picture of how network communications work.

    Protocols (rules) govern communications between the layers of a singlesystem and among several systems. In this way, devices made bydifferent manufacturers or using different designs can use differentprotocols and still communicate.

    By understanding how network troubleshooting fits into theframework of the OSI model, you can identify at what layer problems

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    are located and which type of troubleshooting tools to use. Forexample, unreliable packet delivery can be caused by a problem withthe transmission media or with a router configuration. If you arereceiving high rates of "FCS Errors" and "Alignment Errors" , which youcan monitor with Status Watch, then the problem is probably located at

    the physical layer and not the network layer. Figure 1 shows how totroubleshoot the layers of the OSI model.

    Table 5 describes the data that the network management tools cancollect as it relates to the OSI model layers.

    Table 5 Network Data and the OSI Model Layers

    Layer Data Collected Transcendc NCS Tool

    Used

    Application

    Presentation

    Session

    Transport

    Protocol information and other Remote Monitoring(RMON) and RMON2 data

    LANsentryManager

    Traffix Manager (for more detail)

    Network Routing information

    Status Watch LANsentry

    Manager (for more detail)

    Traffix Manager

    (for more detail)

    Data Link Traffic counts and other packet breakdowns

    Status Watch

    LANsentryManager (for more detail)

    Physical Error counts Status Watch

    Figure 1 OSI Reference Model and Network Troubleshooting

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    For information about network troubleshooting tools, see "YourNetwork Troubleshooting Toolbox" .

    Troubleshooting Strategy

    How do you know when you are having a network problem? Theanswer to this question depends on your site's network configurationand on your network's normal behavior. See "Knowing Your Network "for more information.

    If you notice changes on your network , ask the following questions:

    Is the change expected or unusual? Has this event ever occurred before?

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    Does the change involve a device or network path for which you already have a backup solution in place?

    Does the change interfere with vital network operations? Does the change affect one or many devices or network paths?

    After you have an idea of how the change is affecting your network ,you can categorize it as critical or noncritical. Both of these categoriesneed resolution (except for changes that are one-time occurrences);the difference between the categories is the time that you have to fixthe problem.By using a strategy for network troubleshooting , you can approacha problem methodically and resolve it with minimal disruption tonetwork users. It is also important to have an accurate and detailedmap of your current network environment. Beyond that, a goodapproach to problem resolution is:

    Recognizing Symptoms Understanding the Problem Identifying and Testing the Cause of the Problem Solving the Problem

    Recognizing Symptoms

    The first step to resolving any problem is to identify and interpret thesymptoms. You may discover network problems in several ways.Users may complain that the network seems slow or that they cannotconnect to a server. You may pass your network management stationand notice that a node icon is red. Your beeper may go off and displaythe message: WAN connection down .

    User Comments

    Although you can often solve networking problems before users noticea change in their environment, you invariably get feedback from yourusers about how the network is running, such as:

    They cannot print. They cannot access the application server. It takes them much longer to copy files across the network than it usually does. They cannot log on to a remote server. When they send e-mail to another site, they get a routing error message. Their system freezes whenever they try to Telnet.

    Network Management Software Alerts

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    Network management software, as described in "Your Network Troubleshooting Toolbox" , can alert you to areas of your network that need attention. For example:

    The application displays red (Warning) icons.

    Your weekly Top-N utilization report (which indicates the 10 ports with thehighest utilization rates) shows that one port is experiencing much higher utilization levels than normal.

    You receive an e-mail message from your network management station that thethreshold for broadcast and multicast packets has been exceeded.

    These signs usually provide additional information about the problem,allowing you to focus on the right area.

    Analyzing Symptoms

    When a symptom occurs, ask yourself these types of questions tonarrow the location of the problem and to get more data for analysis:

    To what degree is the network not acting normally (for example,does it now take one minute to perform a task that normallytakes five seconds)?

    On what subnetwork is the user located? Is the user trying to reach a server, end station, or printer on the same subnetwork

    or on a different subnetwork? Are many users complaining that the network is operating slowly or that a

    specific network application is operating slowly? Are many users reporting network logon failures? Are the problems intermittent? For example, some files may print with no

    problems, while other printing attempts generate error messages, make users losetheir connections, and cause systems to freeze.

    Understanding the Problem

    Networks are designed to move data from a transmitting device to areceiving device. When communication becomes problematic, youmust determine why data are not traveling as expected and then find asolution. The two most common causes for data not moving reliablyfrom source to destination are:

    The physical connection breaks (that is, a cable is unplugged orbroken).

    A network device is not working properly and cannot send or receive some or alldata.

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    Network management software can easily locate and report aphysical connection break (layer 1 problem). It is more difficult todetermine why a network device is not working as expected, which isoften related to a layer 2 or a layer 3 problem.

    To determine why a network device is not working properly, look first

    for: Valid service - Is the device configured properly for the type of

    service it is supposed to provide? For example, has Quality of Service (QoS), which is the definition of the transmissionparameters, been established?

    Restricted access - Is an end station supposed to be able to connect with aspecific device or is that connection restricted? For example, is a firewall set upthat prevents that device from accessing certain network resources?

    Correct configuration - Is there a misconfiguration of IP address, subnet mask,gateway, or broadcast address? Network problems are commonly caused by

    misconfiguration of newly connected or configured devices. See "Manager-to-Agent Communication" for more information.

    Identifying and Testing the Cause of the Problem

    After you develop a theory about the cause of the problem, test yourtheory. The test must conclusively prove or disprove your theory.

    Two general rules of troubleshooting are:

    If you cannot reproduce a problem, then no problem existsunless it happens again on its own.

    If the problem is intermittent and you cannot replicate it, you can configure your network management software to catch the event in progress.

    For example, with "LANsentry Manager" , you can set alarms andautomatic packet capture filters to monitor your network and informyou when the problem occurs again. See "Configuring Transcend NCS" for more information.Although network management tools can provide a great deal of information about problems and their general location, you may stillneed to swap equipment or replace components of your network untilyou locate the exact trouble spot.After you test your theory, either fix the problem as described in"Solving the Problem" or develop another theory.

    Sample Problem Analysis

    This section illustrates the analysis phase of a typicaltroubleshooting incident.

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    On your network , a user cannot access the mail server. You need toestablish two areas of information:

    What you know - In this case, the user's workstation cannotcommunicate with the mail server.

    What you do not know and need to test - Can the workstation communicate with the network at all,

    or is the problem limited to communication with theserver? Test by sending a "Ping" or by connecting to otherdevices.

    Is the workstation the only device that is unable to communicate with theserver, or do other workstations have the same problem? Test connectivityat other workstations.

    If other workstations cannot communicate with the server, can theycommunicate with other network devices? Again, test the connectivity.

    The analysis process follows these steps:1 . Can the workstation communicate with any other device on thesubnetwork?

    If no , then go to step 2. If yes , determine if only the server is unreachable.

    If only the server cannot be reached, this suggests a serverproblem. Confirm by doing step 2.

    If other devices cannot be reached, this suggests a connectivity problem inthe network . Confirm by doing step 3.

    2 . Can other workstations communicate with the server?

    If no , then most likely it is a server problem. Go to step 3. If yes , then the problem is that the workstation is not communicating with the

    subnetwork. (This situation can be caused by workstation issues or a network issue with that specific station.)

    3 . Can other workstations communicate with other network devices?

    If no , then the problem is likely a network problem. If yes , the problem is likely a server problem.

    When you determine whether the problem is with the server,subnetwork, or workstation, you can further analyze the problem, asfollows:

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    For a problem with the server - Examine whether the serveris running, if it is properly connected to the network , and if it isconfigured appropriately.

    For a problem with the subnetwork - Examine any device on the path betweenthe users and the server.

    For a problem with the workstation - Examine whether the workstation canaccess other network resources and if it is configured to communicate with that particular server.

    Equipment for Testing

    To help identify and test the cause of problems, have available:

    A laptop computer that is loaded with a terminal emulator, TCP/IPstack, TFTP server, CD-ROM drive (to read the onlinedocumentation), and some key network management

    applications, such as LANsentry

    Manager. With the laptopcomputer, you can plug into any subnetwork to gather andanalyze data about the segment.

    A spare managed hub to swap for any hub that does not have management.Swapping in a managed hub allows you to quickly spot which port is generatingthe errors.

    A single port probe to insert in the network if you are having a problem whereyou do not have management capability.

    Console cables for each type of connector, labeled and stored in a secure place.

    Solving the Problem

    Many device or network problems are straightforward to resolve, butothers yield misleading symptoms. If one solution does not work,continue with another.A solution often involves:

    Upgrading software or hardware (for example, upgrading to anew version of agent software or installing Gigabit Ethernetdevices)

    Balancing your network load by analyzing: What users communicate with which servers What the user traffic levels are in different segments

    Based on these findings, you can decide how toredistribute network traffic.

    Adding segments to your LAN (for example, adding a new switch whereutilization is continually high)

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    Replacing faulty equipment (for example, replacing a module that has port problems or replacing a network card that has a faulty jabber protectionmechanism)

    To help solve problems, have available:

    Spare hardware equipment (such as modules and powersupplies), especially for your critical devices

    A recent backup of your device configurations to reload if flash memory getscorrupted (which can sometimes happen due to a power outage)

    Use the Transcend NCS application suite Network AdminTools to save and reload your software configurations to devices.

    Want to do this for a living? Check out Start Your Own Computer Business

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    Network Cable and HubTroubleshootingDoes the PC (Workstation) see any network resources, servers, otherworkstations? Note that some versions of networking software display"remembered" resources, even when the PC can't access them, soyou'll need to actually click on a given resource to see if it's reallyavailable.Return to Diagnostic Chart Have you recently added a network hub? Is the workstation the firstworkstation on a new hub, being stacked or chained to existing hub(s)?When connecting hubs or switches with twisted pair (RJ-45 connector)cabling, whether 10BaseT or 100BaseT, make sure that you eitherconnect to an "X" port (uplink port), or use a special crossover cable. Acrossover cable, unlike a straight through cable, connects pins 1 and 2on one end to 3 and 6 on the other end, and vice versa. You must use atwisted pair for each for noise protection. If you do have an X or uplinkport, you normally see that it is connected to an adjacent port by a lineor other symbol. You can only use one or the other, since they areusing the same physical circuitry, with the X port making the pairreversal. Some people seem to think that hubs are bullet proof, but I'veseen as many bad hubs and bad ports on hubs as bad network adapters. Hubs also have a power transformer that needs to beplugged into a live outlet.Return to Diagnostic Chart Most network adapters have one or more onboard LEDs to show thestatus of the link and network activity (traffic). If your documentationtells you that you have such a link light, is it lit? No link light indicatesthere's a actual break in your physical layer. Check the physicalconnectors at all points on your network in the failed path, and makesure that you are within all of the limits for your physical layer in termsof number of workstations and distances. On a 10BaseT or 100BaseTnetwork , swap the workstation cable to another port on the hub andsee if it works. While it's possible the adapter or the next port or deviceto which it's connected is bad or powered off, the problem is usuallycaused by the cable. Wireless and IR adapters may fail simply due tothe physical location (blind spot) or distance from the transceiver. Oldcoax networks can have the wrong or missing termination (the mostcommon, Thin Ethernet, requires 50 Ohm terminators at segmentends).Return to Diagnostic Chart

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    Have you cloned the software configuration from another workstationon the network (everything but the unique portion of the IP address,assuming you're set up for TCP/IP)? It's too easy to make a mistakewith which protocol should be the default or with the spelling of aWorkgroup, etc. At an active workstation, go through every option in

    the network setup and print screen every page and sub page thatcomes up. Keep it around for future reference when you run intonetworking problems with a similar workstation. If this is the firstworkstation on the network , or the second on a peer-to-peer, go withthe defaults and make use of the operating system's built introubleshooter, at least in Windows versions. Your problem is mostlikely software configuration, which is far too in depth to address in thechart. When in doubt, reboot.Return to Diagnostic Chart Does the Device Manager see the network adapter and report noconflicts? Try reinstalling the driver and rebooting. In Windows, start by

    deleting the existing network device in Device Manager. If Windowsstill won't recognize the network adapter, it could be a conflict withanother hardware adapter or it could be faulty. If the adapter is built-in,either on the motherboard or in a notebook, try restoring the defaultsin CMOS Setup. Proceed to the Conflict Resolution flowchart.Return to Diagnostic Chart Have you tried a known good cable? Even if the link light is lit, itdoesn't mean your cable is capable of carrying network traffic. Anincredible number of techs make these cables wrong out of sheerlaziness or ignorance. Don't say, "But it's a new cable!" Fourconductors are actually used for normal implementations 10BaseT and

    100BaseT, and the wiring is straight through, 1-1, 2-2, 3-3, 6-6. Pins 1and 2 and pins 3 and 6 must each use a twisted pair, or the longer runswill fail and shorter runs will act unpredictably. Visually inspectconnectors to make sure they are solid and wired properly (i.e. twoshared pairs for 1-2, 3-6). Squint into the transparent connector and tryto take note of the color coding for pins 1, 2, 3 and 6. Then go look atthe other end of the cable and make sure that the color coding is thesame, AND that a pair (i.e, blue, blue stripe) is used for the pair 1 and2 and the pair 3 and 6.Return to Diagnostic Chart

    Take the PC (just the system box which some people call the CPU) to

    another workstation location and swap it out with that PC. If you getright on the network , that tells you that the physical link to thelocation where it failed is bad. That could be the patch cable, the in-wall wiring, or the port on the hub it connects to. If it doesn't work atthe new location, that tells you it's either the network adapter or thesoftware configuration. If it's an add-in adapter and you have a spare,by all means try swapping it out, but the software settings are moreoften the culprit. Make sure the driver is up-to-date and the correct

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    version for the OS, make sure that you have cloned all the settings(except the machine name or final IP address) from a working machine,and try going through the OS troubleshooting steps.Return to Diagnostic Chart Are your network access problems of a random or intermittent

    nature? Check for loose connectors. It's very easy to install a RJ-45connector improperly or fail to crimp it tightly enough to hold to thecable such that it loosens up with just a minor physical movement. Theproblem might also be interference somewhere in the cable run. Makesure it's not draped over the back of a CRT or running directly overflorescent lights or other noisy RF emitters. You could be experiencingsoftware conflicts with other processes on the PC. You can tryeliminating all tasks except the minimal network configuration and dosome large file movements to see if the hardware layer is solid. Morelikely it's simply the loading of the network , a traffic jam, or you'reexceeding the number of simultaneous users supported by the

    hardware (including wireless) or the software.Return to Diagnostic Chart Are you using Shielded Twisted Pair (STP) or any other cable type witha non-signaling shield? Note that this is not the usual case for twistedpair cabling. Make sure that the shield is grounded at one end only, oryou could end up with a ground loop and a constant leakage current. If it's not grounded at either end, it may act as an antenna to pick up anddisperse interference. Also, make sure that your cables, even whengrounded, are intelligently routed. Stay away from transformers, highcurrent junctions, heavy equipment that can induce lots of electricalnoise, though it's primarily the higher frequencies you need to worry

    about.Return to Diagnostic Chart Are you within the physical layer limits for your network ? This appliesto both wired and wireless networks. Don't go by the number in theIEEE standard, use the limit in the hub, switch or base stationdocumentation. Be aware that the distance limitations are based on anormal operating environment with the proper cabling or antennasinstalled. If your cables are made wrong, routed poorly, or are lowquality, the limits will be reduced. Rerouting cables, adding repeaters(amplifiers) or eliminating sources of interference can increase thereach of your network .

    Return to Diagnostic Chart Have you tried a different port on the hub? There's no rule that sayshubs have to fail all at once, and even though a performancedegradation of a single port is a rarity, it's worth trying. It could also bethat the cable end plugged into the hub wasn't crimped on as tightly asit could have been, causing the performance of the link to bedependent on the exact position of the cable, an unacceptablesituation.

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    Return to Diagnostic Chart Does the problem, be it lost connections, slow performance or anythingelse, occur during periods when network traffic is high or a largenumber of users are logged on? There are many reasons a network can bog down or have trouble in high traffic or high user count

    situations, including the natural limitations of the technologies beingused. In general, if you are using a passive hub, you can greatlyincrease your network performance during high traffic periods byswapping the hub for an active switch. Also, if you are running a hybridLAN, with a mix of 10BaseT and 100BaseT adapters, you shouldupgrade them all to 100BaseT, providing the cable plant is all Cat 5,which it better be!Return to Diagnostic Chart Is the PC flaky when it's not on the network ? If so, don't waste anymore time on network diagnostics, proceed to Motherboard, CPU andRAM failure and look for the symptoms the PC is displaying. This isn't a

    good test of software problems, since you run different applicationsand have different resource usage when you're connected to thenetwork .Return to Diagnostic Chart

    You should always have a proven long bypass cable for testing, thatyou can run directly from the workstation to the hub without goingthrough walls, ceilings, etc. Make sure you are within the distancelimits for twisted pair, wireless and IR, and within the total number of active stations limit for wireless and IR. Check for physical cabledamage. The sheathing on the Cat 5 cables is thin and the innerconductors can be easily broken if the cable is stretched or crimped.

    Return to Diagnostic Chart Does a new network adapter fix the problem? New PCI network adapters cost less than $10, so there's no reason not to try one. If you're running a wireless network with notebooks and add on wirelessadapters, borrow one from a good unit. If the new network adapterhasn't fixed the problem and you've gone through all the physical layerdiagnostics to get here, it's a software issue.

    Issue:

    Basic network troubleshooting .

    Cause:

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    If a computer is unable to connect to a network or seeother computers on a network , it may be necessary totroubleshoot the network . A network may not workbecause of any of the below reasons.

    1. Network card not connected properly.2. Bad network card drivers or software settings.3. Firewall preventing computers from seeing each other.4. Connection related issues.5. Bad network hardware.

    Solution:Because of the large variety of network configurations, operatingsystems, setup, etc... not all of the below information may apply toyour network or operating system. If your computer is connected to acompany or large network , or you are not the administrator of thenetwork , it is recommended that if you are unable to resolve yourissues after following the below recommendations that you contact thenetwork administrator or company representative.Note: If you are being prompted for a Network password and do notknow the password, Computer Hope is unable to assist users withobtaining a new or finding out the old password.

    Verify connections / LEDs

    Verify that the network cable is properly connected to theback of the computer. In addition, when checking theconnection of the network cable, ensure that the LEDs onthe network are properly illuminated. For example, anetwork card with a solid green LED or light usuallyindicates that the card is either connected or receiving asignal. Note: generally, when the green light is flashing,this is an indication of data being sent or received.

    If, however, the card does not have any lights or hasorange or red lights, it is possible that either the card isbad, the card is not connected properly, or that the card is

    not receiving a signal from the network .If you are on a small or local network and have thecapability of checking a hub or switch, verify that thecables are properly connected and that the hub or switchhas power.

    Adapter resources

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    Ensure that if this is a new network card being installedinto the computer that the card's resources are properlyset and/or are not conflicting with any hardware in thecomputer.

    Users who are using Windows 95, 98, ME, 2000 or XP,verify that device manager has no conflicts or errors.Additional help and information about device manager andresources can be found on our device manager page .

    Adapter functionality

    Verify that the network card is capable of pinging orseeing itself by using the ping command. Windows / MS-DOS users ping the computer from a MS-DOS prompt. Unix/ Linux variant users ping the computer from the shell.

    To ping the card or the localhost, type either

    ping 127.0.0.1

    or

    ping localhost

    This should show a listing of replies from the network card. If you receive an error or if the transmission failed, itis likely that either the network card is not physicallyinstalled into the computer correctly, or that the card isbad.

    Protocol

    Verify that the correct protocols are installed on thecomputer. Most networks today will utilize TCP/IP , but mayalso utilize or require IPX/SPX and NetBEUI .

    Additional information and help with installing andreinstalling a network protocol can be found on documentCH000470 .

    When the TCP/IP protocol is installed, unless a DNS serveror other computer assigns the IPX address, the user mustspecify an IP address as well as a Subnet Mask . To do this,follow the below instructions.

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    1. Click Start / Settings / Control Panel2. Double-click the Network icon3. Within the configuration tab double-click the TCP/IP

    protocol icon. Note: Do not click on the PPP or Dial-Upadapter, click on the network card adapter.

    4. In the TCP/IP properties click the IP address tab5. Select the option to specify an IP address6. Enter the IP address and Subnet Mask address, an

    example of such an address could be:

    IP Address: 102.55.92.1Subnet Mask: 255.255.255.192

    7. When specifying these values, the computers on thenetwork must all have the same Subnet Mask andhave a different IP Address. For example, when using

    the above values on one computer you would wantto use an IP address of 102.55.92.2 on anothercomputer and then specify the same Subnet Mask.

    Firewall

    If your computer network utilizes a firewall , ensure that allports required are open. If possible, close the firewallsoftware program or disconnect the computer from thefirewall to ensure it is not causing the problem.

    Additional time

    In some cases it may take a computer some additionaltime to detect or see the network . If after booting thecomputer you are unable to see the network , give thecomputer 2-3 minutes to detect the network . Windowsusers may also want to try pressing the F5 (refresh) keywhen in Network Neighborhood to refresh the network connections and possibly detect the network .

    Additional troubleshooting

    If after following or verifying the above recommendationsyou are still unable to connect or see the network ,attempt one or more of the below recommendations.

    If you have installed or are using TCP/IP as your protocolyou can attempt to ping another computer's IP address toverify if the computer is able to send and receive data. To

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    do this, Windows or MS-DOS users must be at a promptand Linux / Unix variant users must open or be at a shell.

    Once at the prompt assuming, that the address of thecomputer you wish to attempt to ping is 102.55.92.2, you

    would type:

    ping 102.55.92.2

    If you receive a response back from this address (and it is adifferent computer), this demonstrates that the computeris communicating over the network . If you are still unableto connect or see the network , it is possible that otherissues may be present.

    Another method of determining network issues is to use

    the tracert command if you are a MS-DOS or Windows useror the traceroute command if you are a Linux / Unix variantuser. To use this command you must be at the commandprompt or shell.

    Once at the prompt, assuming that the address is again102.55.92.2, type:

    tracert 102.55.92.2

    or

    traceroute 102.55.92.2

    This should begin listing the hops between the computerand network devices. When the connection fails,determine which device is causing the issue by reviewingthe traceroute listing.