Network Troubleshooting


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Network Troubleshooting

  1. 1. Chapter 13 Network Troubleshooting
  2. 2. Introduction <ul><li>Look at: </li></ul><ul><ul><li>Avoiding Potential Problems (13.1) </li></ul></ul><ul><ul><li>Principles of Troubleshooting (13.2) </li></ul></ul><ul><ul><li>Accessing Key Information Resources (13.3) </li></ul></ul><ul><ul><li>Handling Common Sources of Trouble (13.4) </li></ul></ul>
  3. 3. Avoiding Potential Problems <ul><li>There are two approaches to trouble shooting: </li></ul><ul><ul><li>preventing potential problems through proper planning </li></ul></ul><ul><ul><li>quickly fixing what fails </li></ul></ul><ul><li>The former is often referred to as trouble avoidance or pre-emptive troubleshooting </li></ul><ul><li>The later is referred to as troubleshooting or damage control </li></ul>
  4. 4. Avoiding Potential Problems <ul><li>To be effective, both should be used in combination </li></ul><ul><li>Be proactive in managing the environment </li></ul><ul><li>Know how to effectively troubleshoot any issue </li></ul><ul><li>Documentation is important </li></ul><ul><li>It's a tedious job but it is imperative that you have proper documentation </li></ul>
  5. 5. Avoiding Potential Problems <ul><li>Ensure that users have ongoing access by making sure that if something happens you have a backup plan: </li></ul><ul><ul><li>Identify the data that should be backed up </li></ul></ul><ul><ul><li>Determine the backup type and schedule </li></ul></ul><ul><ul><li>Designate someone to be responsible </li></ul></ul><ul><ul><li>Be sure the tapes are properly labeled </li></ul></ul><ul><ul><li>Keep a log </li></ul></ul>
  6. 6. Avoiding Potential Problems <ul><li>Security policy should detail hardware and software along with some of these areas: </li></ul><ul><ul><li>Clear paths of responsibility and user expectations </li></ul></ul><ul><ul><li>Awareness of privacy issues that may arise </li></ul></ul><ul><ul><li>A separation of duties, so that total control is not left in the hands of a single individual </li></ul></ul>
  7. 7. Avoiding Potential Problems <ul><li>Security policy should detail hardware and software along with some of these areas: </li></ul><ul><ul><li>Password length, duration, history, and complexity requirements </li></ul></ul><ul><ul><li>A clear policy for the destruction of data </li></ul></ul><ul><ul><li>Procedures for creating and authorizing accounts </li></ul></ul><ul><ul><li>Incident response and disaster recovery planning policies </li></ul></ul>
  8. 8. Avoiding Potential Problems <ul><li>The goal of security is expressed in terms of: </li></ul><ul><ul><li>Confidentiality </li></ul></ul><ul><ul><li>Integrity </li></ul></ul><ul><ul><li>Availability </li></ul></ul><ul><li>These goals can be achieved through creating hardware and software standards </li></ul>
  9. 9. Avoiding Potential Problems <ul><li>Workstation consistency is often overlooked: </li></ul><ul><ul><li>Installing unauthorized software </li></ul></ul><ul><ul><li>Downloading infected music and movie files </li></ul></ul><ul><ul><li>Opening an e-mail message that contain a virus </li></ul></ul><ul><ul><li>Using weak passwords </li></ul></ul><ul><ul><li>Not logging off the network when leaving the building </li></ul></ul>
  10. 10. Avoiding Potential Problems <ul><li>Standards for laptops, personal digital assistants (PDAs), Palm Pilots, and Pocket PCs may be more difficult to define </li></ul><ul><li>If these devices are company issued or company supported, they must be standardized as well </li></ul><ul><li>These devices are susceptible to theft because they are small and valuable. </li></ul><ul><li>Many times contain important information about the company </li></ul>
  11. 11. Avoiding Potential Problems <ul><li>You must also define and document standards for new server installations along with guidelines for current server configurations </li></ul><ul><li>The configuration process should start with installing only the services necessary for the server to function </li></ul><ul><li>Limit physical access to the server </li></ul><ul><li>Use Redundant Array of Inexpensive Disk (RAID), uninterruptible power supply (UPS) equipment, and clustering </li></ul>
  12. 12. Avoiding Potential Problems <ul><li>Policies should include provisions for change authorization, documentation, and notification </li></ul><ul><li>Include procedures to be used when hardware, software, or storage media is replaced or discarded </li></ul><ul><li>Planning and testing can eliminate corruption or data deletion problems </li></ul><ul><li>Sufficient time must be spent to ensure that the transition goes as smoothly as possible </li></ul>
  13. 13. Avoiding Potential Problems <ul><li>The following should be considered when creating a change in management policy: </li></ul><ul><ul><li>Establish a schedule for changes </li></ul></ul><ul><ul><li>Make sure users are notified of the changes </li></ul></ul><ul><ul><li>Conduct proper testing </li></ul></ul><ul><li>Changes should be scheduled during off hours </li></ul>
  14. 14. Avoiding Potential Problems <ul><li>Documentation is critical </li></ul><ul><li>Before actually deploying the change, testing should be conducted </li></ul><ul><li>Testing should be well documented </li></ul><ul><li>A rollback strategy should be part of every change plan </li></ul>
  15. 15. Avoiding Potential Problems <ul><li>Thorough documentation is a necessary part of an administrator's job </li></ul><ul><li>Document everything you do and be as detailed as you can </li></ul><ul><li>Documenting is particularly important because of the impact it can have on business if legal action is involved </li></ul><ul><li>All documents should be kept in both hard- and soft-copy form </li></ul>
  16. 16. Avoiding Potential Problems <ul><li>Your network documentation should include these components: </li></ul><ul><ul><li>Policies and procedures </li></ul></ul><ul><ul><li>Network history </li></ul></ul><ul><ul><li>Network map </li></ul></ul><ul><ul><li>Cable diagrams and layouts </li></ul></ul><ul><ul><li>Contact list </li></ul></ul><ul><ul><li>Equipment list </li></ul></ul>
  17. 17. Avoiding Potential Problems <ul><li>Your network documentation should include these components: </li></ul><ul><ul><li>Computer and network device configuration </li></ul></ul><ul><ul><li>Software and its configuration </li></ul></ul><ul><ul><li>Network address list </li></ul></ul><ul><ul><li>Software licensing information </li></ul></ul>
  18. 18. Avoiding Potential Problems <ul><li>Pre-emptive troubleshooting is also called trouble avoidance </li></ul><ul><li>It will save time and may help save data when problems arise </li></ul><ul><li>Pre-emptive troubleshooting can also prevent additional expense and downtime while trying to figure out what happened after a failure </li></ul>
  19. 19. Avoiding Potential Problems <ul><li>The ISO defines five pre-emptive troubleshooting network management categories: </li></ul><ul><ul><li>Accounting management </li></ul></ul><ul><ul><li>Configuration management </li></ul></ul><ul><ul><li>Fault management </li></ul></ul><ul><ul><li>Performance management </li></ul></ul><ul><ul><li>Security management </li></ul></ul>
  20. 20. Avoiding Potential Problems <ul><li>The measure of normal network activity is known as a baseline </li></ul><ul><li>This gives you a point of reference when the network goes awry </li></ul><ul><li>Baselining should be done for both network and application processes </li></ul><ul><li>The allows you to determine whether you have a hardware or software issue </li></ul>
  21. 21. Avoiding Potential Problems <ul><li>There are tools can be used to gather network information </li></ul><ul><li>Event Viewer allows you to audit certain events </li></ul><ul><li>Task manager can be used to end processes or applications that get hung up without having to reboot the machine </li></ul><ul><li>Auditing is the process of tracking users and their actions on the network </li></ul>
  22. 22. Avoiding Potential Problems <ul><li>Keep in mind that auditing uses system resources and space </li></ul><ul><li>The Performance console is used for tracking and viewing the utilization of operating system resources </li></ul><ul><li>A network monitor can be used to capture network traffic and generate statistics for creating reports </li></ul>
  23. 23. Principles of Troubleshooting <ul><li>Troubleshooting requires skill </li></ul><ul><li>These skills are acquired through experimentation and experience </li></ul><ul><li>You cannot learn the resolution to every problem that exists </li></ul><ul><li>You can, however, learn a methodology to find and diagnose nearly every problem in a systematic and logical manner </li></ul>
  24. 24. Principles of Troubleshooting <ul><li>The following are the most common network problems: </li></ul><ul><ul><li>User error </li></ul></ul><ul><ul><li>Physical connections </li></ul></ul><ul><ul><li>System needs a reboot </li></ul></ul><ul><li>If these steps don't help, then it's time to move on and try other troubleshooting options </li></ul>
  25. 25. Principles of Troubleshooting <ul><li>Research on problem solving and reasoning is fundamental to understanding troubleshooting skills </li></ul><ul><li>You can choose from several different methodologies of troubleshooting </li></ul><ul><li>These give us guidelines for logical solving problems using a step-by-step process </li></ul>
  26. 26. Principles of Troubleshooting <ul><li>The first step is to determine the scope of the problem by identifying the symptoms </li></ul><ul><li>The next step is to collect specific information about the problem at hand </li></ul><ul><li>Once you have the pertinent information, then the scope is determined </li></ul><ul><li>Begin to isolate the problem by testing each of the causes, starting with the most obvious first </li></ul>
  27. 27. Principles of Troubleshooting <ul><li>Attempt to re-create the problem </li></ul><ul><li>Make only one change at a time </li></ul><ul><li>Test each change </li></ul><ul><li>Don't be afraid to ask for help </li></ul><ul><li>Read the documentation that came with the hardware or software </li></ul><ul><li>Don't forget about the obvious </li></ul>
  28. 28. Principles of Troubleshooting <ul><li>Creating a Hardware Toolkit: </li></ul><ul><ul><li>Crossover cable </li></ul></ul><ul><ul><li>Hardware loopback adapter </li></ul></ul><ul><ul><li>Tone generator </li></ul></ul><ul><ul><li>Cable tester or cable checker </li></ul></ul><ul><ul><li>Voltmeters </li></ul></ul><ul><ul><li>Time domain reflectometer (TDR) </li></ul></ul><ul><ul><li>Oscilloscope </li></ul></ul>
  29. 29. Principles of Troubleshooting <ul><li>Creating a Software Toolkit: </li></ul><ul><ul><li>Ping </li></ul></ul><ul><ul><li>Netstat </li></ul></ul><ul><ul><li>Nbtstat </li></ul></ul><ul><ul><li>Traceroute </li></ul></ul><ul><ul><li>Network monitors </li></ul></ul><ul><ul><li>Protocol analyzer </li></ul></ul>
  30. 30. Accessing Key Information Resources <ul><li>One of the best places for troubleshooting a problem is the manufacturer's Web site </li></ul><ul><li>Subscription services such as TechNet can be used to obtain a wealth of information </li></ul><ul><li>Vendor-provided CDs should be one of the first places you go to look for information </li></ul><ul><li>Look at the readme.txt file even before the product is installed </li></ul>
  31. 31. Accessing Key Information Resources <ul><li>Resource kits are another excellent source of information about your operating system </li></ul><ul><li>Call the vendor and open up a technical support incident to solve the problem </li></ul><ul><li>If it is a known issue the vendor may have documented fixes available </li></ul>
  32. 32. Accessing Key Information Resources <ul><li>Have the following information ready to assist the support department: </li></ul><ul><ul><li>The operating system you are running </li></ul></ul><ul><ul><li>Service packs that are installed </li></ul></ul><ul><ul><li>Version numbers of hardware and software </li></ul></ul><ul><ul><li>Serial numbers </li></ul></ul><ul><ul><li>Detailed account of the problem and troubleshooting steps you have taken </li></ul></ul>
  33. 33. Accessing Key Information Resources <ul><li>Other excellent sources of information are periodicals and white papers </li></ul><ul><li>Many new magazines and periodicals are introduced each year, some of them deal with specific computing environments </li></ul><ul><li>Besides white papers and periodicals, don’t forget to keep a couple of good reference books handy, especially when you first start out </li></ul>
  34. 34. Handling Common Sources of Trouble <ul><li>Not all problems will be easy to fix </li></ul><ul><li>The two most common causes for data not moving reliably are: </li></ul><ul><ul><li>A physical connection breaks such as the cable being unplugged or broken </li></ul></ul><ul><ul><li>A network device is not working properly </li></ul></ul>
  35. 35. Handling Common Sources of Trouble <ul><li>The majority of networking problems occur at the Physical layer of the OSI model and include problems with: </li></ul><ul><ul><li>cables </li></ul></ul><ul><ul><li>connectors </li></ul></ul><ul><ul><li>NICs </li></ul></ul><ul><li>Check cabling and connections first during your network troubleshooting process </li></ul>
  36. 36. Handling Common Sources of Trouble <ul><li>Power problems will crop up in various ways </li></ul><ul><li>One of the most obvious is when power strips are daisy chained together </li></ul><ul><li>The devices will not get enough power </li></ul><ul><li>The other end of the spectrum is that this will occasionally trip the circuit breakers or start a fire </li></ul>
  37. 37. Handling Common Sources of Trouble <ul><li>Power not properly conditioned, can have devastating effects on equipment : </li></ul><ul><ul><li>Noise </li></ul></ul><ul><ul><li>Spikes </li></ul></ul><ul><ul><li>Surges and overvoltages </li></ul></ul><ul><ul><li>Sags and brownouts </li></ul></ul><ul><ul><li>Blackouts </li></ul></ul>
  38. 38. Handling Common Sources of Trouble <ul><li>Always connect your sensitive electronic equipment to: </li></ul><ul><ul><li>power conditioners </li></ul></ul><ul><ul><li>surge protectors </li></ul></ul><ul><ul><li>for the best protection an uninterruptible power supply (UPS) </li></ul></ul><ul><li>The UPS powers the computer so that you can take action without data loss </li></ul>
  39. 39. Handling Common Sources of Trouble <ul><li>There are basically three different types of devices that are classified as UPSs: </li></ul><ul><ul><li>Standby power supply (SPS) </li></ul></ul><ul><ul><li>Hybrid or ferroresonant UPS systems </li></ul></ul><ul><ul><li>Continuous UPS </li></ul></ul><ul><li>Never plug a printer into a UPS </li></ul><ul><li>Power problems cannot be eliminated but the damage can be minimized or prevented </li></ul>
  40. 40. Handling Common Sources of Trouble <ul><li>A software upgrade can cause issues on the system even though you tested the upgrade </li></ul><ul><li>You should be prepared to rollback or reverse the process. </li></ul><ul><li>This process is also referred to as backleveling </li></ul><ul><li>Most often the best source of help when a problem occurs is the manufacturer's documentation </li></ul>
  41. 41. Handling Common Sources of Trouble <ul><li>You will also have to provide for a backup plan in the event a hardware upgrade doesn't go as planned </li></ul><ul><li>It is important not the discard the old device in the event the upgrade causes issues </li></ul><ul><li>This applies to the drivers that may be necessary as well </li></ul>
  42. 42. Handling Common Sources of Trouble <ul><li>The complexity of network topology and communication equipment has become more and more sophisticated </li></ul><ul><li>Performance management as well as response time management is more difficult </li></ul><ul><li>Sometimes you will find that for an unknown reason the network performance begins to suffer </li></ul>
  43. 43. Handling Common Sources of Trouble <ul><li>Here are some avenues for you to consider when there are issues with performance: </li></ul><ul><ul><li>Change is the biggest factor that can cause poor network performance </li></ul></ul><ul><ul><li>Another big factor that affects network performance is playing games or downloading music and movie files </li></ul></ul>
  44. 44. Handling Common Sources of Trouble <ul><li>Here are some avenues for you to consider when there are issues with performance: </li></ul><ul><ul><li>Sometimes applications have memory leaks or a new version may be bloated or have an improperly programmed query function </li></ul></ul><ul><ul><li>Adding new electrical equipment may have a negative effect on the network </li></ul></ul>
  45. 45. Handling Common Sources of Trouble <ul><li>Here are some avenues for you to consider when there are issues with performance: </li></ul><ul><ul><li>Adding new hardware such as additional servers or workstations may cause performance to decrease </li></ul></ul><ul><ul><li>Other changes in workload or workplace behavior, including adding more users, could affect performance </li></ul></ul>