Network Guide to Networks, Fourth Edition Chapter 12 ...

Network+ Guide to Networks, Fourth Edition Chapter 12 Troubleshooting Network Problems Objectives •! Describe the steps involved in an effective troubleshooting methodology •! Follow a systematic troubleshooting process to identify and resolve networking problems •! Document symptoms, solutions, and results when troubleshooting network problems •! Use a variety of software and hardware tools to diagnose problems Network+ Guide to Networks, 4E 2 Troubleshooting Methodology •! Steps for troubleshooting network problems: –! Identify symptoms and potential causes –! Identify affected area –! Establish what has changed –! Select most probable cause •! Verify user competency •! Re-create problem •! Verify physical integrity of network connection •! Verify logical integrity of network connection Network+ Guide to Networks, 4E 3 Troubleshooting Methodology (continued) •! Steps for troubleshooting network problems (continued): –! Implement an action plan and solution and be prepared for all potential effects –! Test the result –! Identify results and effects of solution –! Document solution and process Network+ Guide to Networks, 4E 4 Identify the Symptoms and Potential Causes •! Questions that may help identify non-obvious symptoms: –! Access to network affected? –! Network performance affected? –! Data and/or programs affected? –! Only certain network services affected? –! Problems include local application, networked application, or multiple networked applications? –! Specific error messages reported? –! One user or multiple users affected? –! Symptoms manifested consistently? Network+ Guide to Networks, 4E 5 Identify the Affected Area Figure 12-1: Identifying the area affected by a problem Network+ Guide to Networks, 4E 6 Identify the Affected Area (continued) Figure 12-1 (continued): Identifying the area affected by a problem Network+ Guide to Networks, 4E 7 Identify the Affected Area (continued) Figure 12-2: Identifying the chronological scope of a problem Network+ Guide to Networks, 4E 8 Identify the Affected Area (continued) Figure 12-2 (continued): Identifying the chronological scope of a problem Network+ Guide to Networks, 4E 9 Establish What Has Changed •! Questions to help pinpoint problems resulting from a network change: –! OS or configuration on a server, workstation, or connectivity device changed? –! New components added to server, workstation, or connectivity device? –! Old components removed from server, workstation, or connectivity device? –! New users or segments added to the network? –! Server, workstation, or connectivity device moved from previous location to new location? Network+ Guide to Networks, 4E 10 Establish What Has Changed (continued) •! Questions to help pinpoint problems resulting from a network change (continued): –! Was a server, workstation, or connectivity device replaced? –! Was new software installed on a server, workstation, or connectivity device? –! Was old software removed from a server, workstation, or connectivity device? Network+ Guide to Networks, 4E 11 Establish What Has Changed (continued) •! Two ways to react to problems caused by network changes: –! Attempt to correct problem –! Attempt to reverse change and restore hardware or software to previous state •! Complete network change records should be kept –! Make available to staff members Network+ Guide to Networks, 4E 12 Select the Most Probable Cause: Verify User Competency •! Ensure that human error is not source of problem •! Problems caused by human error usually simple to solve •! Best way to verify that a user is performing network tasks correctly is to watch them Network+ Guide to Networks, 4E 13 Re-create the Problem •! Try to reproduce symptoms both while logged on as the user who reported the problem and while logged on under a privileged account •! Questions to help determine whether a problem’s symptoms are truly reproducible: –! Make symptoms recur every time? –! Make symptoms recur some of the time? –! Symptoms happen only under certain circumstances? –! Symptoms consistent no matter how many and which programs or files user has open? Network+ Guide to Networks, 4E 14 Verify Physical Connectivity •! Many network problems occur at Physical layer –! Symptoms of Physical Layer problems: continuous or intermittent inability to connect to network and perform network related functions –! Possible causes of Physical Layer problems: •! Segment or network lengths exceeding IEEE maximum standards •! Noise affecting wireless or wire-bound signal •! Improper terminations, faulty connectors, loose connectors, or poorly crimped connections •! Damaged cables •! Faulty NICs Network+ Guide to Networks, 4E 15 Verify Physical Connectivity (continued) •! Diagnosing Physical Layer problems: –! Device turned on? –! NIC properly inserted? –! For wireless NICs, antenna turned on? –! Device’s network cable properly connected to both NIC and wall jack? –! Patch cables properly connect punch-down blocks to patch panels and patch panels to hubs or switches? Network+ Guide to Networks, 4E 16 Verify Physical Connectivity (continued) •! Diagnosing Physical Layer problems (continued): –! Hub, router, or switch properly connected to backbone? –! Cables in good condition? –! Connectors in good condition and properly seated? –! Network lengths conform to IEEE 802 specifications? –! Devices configured properly to work with network type or speed? Network+ Guide to Networks, 4E 17 Verify Physical Connectivity (continued) •! Swapping equipment: –! If you suspect problem lies with a network component, easy to test theory by exchanging for a functional component –! Cables, ports, data jacks, network adapters –! Difficult to swap routers and switches Network+ Guide to Networks, 4E 18 Verify Physical Connectivity (continued) Figure 12-3: Verifying physical connectivity Network+ Guide to Networks, 4E 19 Verify Physical Connectivity (continued) Figure 12-3 (continued): Verifying physical connectivity Network+ Guide to Networks, 4E 20