Monday at 1600. The only person authorized to use the LAN after 1600 is PO1 Brush, who is the network administrator. You call PO1 Brush and ask if any changes were made to the word processing program since yesterday. PO1 Brush states he installed a new version of the word processing program on Monday around 2200 to eliminate any work disruptions. You ask him to check the security access to this new version. You find PO1 Brush inadvertently restricted all users from accessing the new version of the word processing program after he removed the old one. He makes the necessary access changes, and everybody is once again happy and able to use the new version. As you can see, there is a pattern to the various types of  errors/problems  you  will  encounter.  The  problems you will be confronted with will range from the simple to  the  disastrous.  They  may  be  user/operator  errors, software   problems,   or   hardware   malfunctions. Knowing  which  is  sometimes  easy.  Under  other conditions, it may be difficult for you to determine the source of the problem. The important thing is to learn from your past experiences. Keep a list of symptoms, probable causes, and ways you can use to trace a problem to its cause. This will assist you in diagnosing and troubleshooting problems. You will also find users have a tendency to make the same mistakes again and again, especially while they are learning. You can provide them a great service by explaining some of the more common problems they are likely to encounter, the reasons for the problems, and ways to avoid having them happen to them. NETWORK  MALFUNCTIONS Any malfunction of the network is going to result in a  nonavailability  of  the  system  to  the  users.  The diagnosis and fixing of this malfunction becomes a high priority. There are three primary culprits to network malfunctions: component and server failures, and data collisions. COMPONENT FAILURE Component   failures   are   categorized   in   two categories: hard faults and soft faults. Hard faults are relatively easy to find, and a diagnostic program will diagnose them correctly every time. Soft faults can be difficult to find, because they occur sporadically or only under  specific  circumstances,  rather  than  every  time  the memory location is tested. A diagnostic program tests computer hardware and peripheral devices for correct operation. Most computers run a simple set of system checks when the computer is turned on. The PC tests are stored in  read-only  memory  (ROM),  and  are  known  as  power- on self tests (POSTs). If a POST detects an error condition, the computer will stop and display an error on the screen. Some computers will emit a beep signal to indicate the type of error. One  of  the  best  tools  to  use  for  network malfunctions is a network analyzer. A network analyzer is a product that can be used to monitor the activity of a network  and  the  stations  on  it,  and  to  provide  daily summaries or long-term trends of network usage and performance. A network analyzer can do tasks such as: l l l l l Count or filter network traffic. Analyze  network  activity  involving  specified protocols or frame structures. Generate, display, and print statistics about network  activity,  either  as  they  are  being generated or in summary form. Send alarms to a network supervisor or network management program if any of the statistics being monitored exceeds predetermined limits. Do trend or pattern analyses of network activity. Network  analyzers  may  be  software  only  or  consist of both software and hardware. The latter may include an interface card enabling you to test the network directly. This card may include an on-board processor. Because  of  their  greater  capabilities,  hardware/software analyzers are more expensive than the software only analyzers. In fact, the prices for the hardware/software analyzers can be several times as high as those for the software only versions. SERVER   FAILURE The most obvious sign that the server has failed for some reason is that all users, except root, will not be able to logon to the system. Use the following steps as required to reestablish services: The first and easiest thing to try is to run the system distribution again. This will rebuild the system maps if nothing else is wrong and will allow users access to the system. Shutdown  and  reboot  the  system.  During  the boot process ensure that no failures occur on any of the nodes. 3-3