NETWORK+ GUIDE TO NETWORKS, FOURTH EDITION - CHAPTER 12 ppt

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 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 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 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 Identify the Affected Area Figure 12-1: Identifying the area affected by a problem Network+ Guide to Networks, 4E Identify the Affected Area (continued) Figure 12-1 (continued): Identifying the area affected by a problem Network+ Guide to Networks, 4E Identify the Affected Area (continued) Figure 12-2: Identifying the chronological scope of a problem Network+ Guide to Networks, 4E Identify the Affected Area (continued) Figure 12-2 (continued): Identifying the chronological scope of a problem Network+ Guide to Networks, 4E 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 Network Monitors • Software tool that continually monitors network traffic from a server or workstation – Typically can interpret up to Layer – Determines protocols passed by each frame – Can’t interpret data inside frames • Many available programs: – Microsoft Network Monitor ships with Windows Server 2003 – Novell NETMON comes with NetWare 5.x and 6.x – Many others available Network+ Guide to Networks, 4E 41 Network Monitors (continued) • Network monitoring tools perform following functions: – – – – Continuously monitor network traffic on segment Capture network data transmitted on segment Capture frames sent to or from specific node Reproduce network conditions by transmitting selected amount and type of data – Generate statistics about network activity Network+ Guide to Networks, 4E 42 Network Monitors (continued) • Some network monitoring tools can also: – Discover all network nodes on a segment – Establish a baseline • Record of how network operates under normal conditions, including performance, collision rate, utilization rate, and so on – Store traffic data and generate reports – Trigger alarms when traffic conditions meet preconfigured conditions Network+ Guide to Networks, 4E 43 Network Monitors (continued) • Data errors that can be distinguished: – – – – – – – Local collisions Late collisions Runts Giants Jabber Negative frame sequence checks Ghosts Network+ Guide to Networks, 4E 44 Protocol Analyzers • Capture traffic and analyze frames – Typically up to Layer – Can interpret payload portion of frames • Can generate traffic in attempt to reproduce network problem and monitor multiple network segments simultaneously • Hardware-based protocol analyzers exist – Sole job is to identify and assess network problems – Tailored to particular type of network • May collect more information than can be processed Network+ Guide to Networks, 4E 45 Protocol Analyzers (continued) Figure 12-8: Traffic displayed by protocol type Network+ Guide to Networks, 4E 46 Wireless Network Testers • To test wireless connections, stations, or APs, need tools that contain wireless NICs and run wireless protocols • Programs exist that can scan for wireless signals over a geographical range and discover all APs and wireless stations transmitting in area – Determine whether AP functioning properly – Determine whether AP positioned correctly – Determine whether stations and APs are communicating over proper channels within a frequency band Network+ Guide to Networks, 4E 47 Wireless Network Testers (continued) • Some programs can capture data transmitted between stations and APs – Useful for troubleshooting wireless connection problems • Some programs contain a spectrum analyzer – Assess quality of wireless signal – Ascertain where noise (or interference) is greatest Network+ Guide to Networks, 4E 48 Wireless Network Testers (continued) • Capabilities common to wireless network testers: – Identify transmitting APs and stations and channels over which they are communicating – Measure signal strength from and determine range of AP – Indicate effects of attenuation, signal loss, and noise – Interpret signal strength information Network+ Guide to Networks, 4E 49 Wireless Network Testers (continued) • Capabilities common to wireless network testers (continued): – Ensure proper association and reassociation when moving between APs – Capture/interpret traffic exchanged between wireless APs and stations – Measure throughput and assess data transmission errors – Analyze the characteristics of each channel within a frequency band to indicate the clearest channels Network+ Guide to Networks, 4E 50 Wireless Network Testers (continued) Figure 12-10: Wireless network testing tool Network+ Guide to Networks, 4E 51 Summary • Key to solving network problems is to approach them methodically and logically, using your experience to inform your decisions, and knowing when to ask for someone else’s help • First step in troubleshooting is identifying the symptoms and potential causes for a problem • Second step in troubleshooting is to identify the affected area • At each point in the troubleshooting process, stop to consider what kind of changes have occurred on the network that might have created a problem Network+ Guide to Networks, 4E 52 Summary (continued) • Based on an analysis of the symptoms and how changes might have affected the network, select a probable cause for the problem • After you have identified the probable cause, implement an action plan and your solution, while considering the potential effects of the solution • After implementing your solution, test your result to ensure that you solved the problem and haven’t created new problems • Next identify the effects and results of your solution Network+ Guide to Networks, 4E 53 Summary (continued) • Last step in troubleshooting is to document the solution and the process of solving the problem • A tone generator and tone locator are used to identify the terminating location of a wire pair • A multimeter is a simple device that can measure the voltage, resistance, impedance, and other characteristics of an electrical circuit • Basic cable continuity testers determine whether your cabling can provide connectivity Network+ Guide to Networks, 4E 54 Summary (continued) • A network monitor is a software-based tool that monitors network traffic from a server or workstation attached to the network • Protocol analyzers can typically interpret data up to Layer of the OSI Model • Wireless network testing tools can be dedicated instruments or software that run on a workstation (usually a laptop) Network+ Guide to Networks, 4E 55 ... certain type of network Network+ Guide to Networks, 4E 33 Tone Generator and Tone Locator (continued) Figure 1 2-4 : Use of a tone generator and tone locator Network+ Guide to Networks, 4E 34 Multimeter... processed Network+ Guide to Networks, 4E 45 Protocol Analyzers (continued) Figure 1 2-8 : Traffic displayed by protocol type Network+ Guide to Networks, 4E 46 Wireless Network Testers • To test wireless... frequency band to indicate the clearest channels Network+ Guide to Networks, 4E 50 Wireless Network Testers (continued) Figure 1 2-1 0: Wireless network testing tool Network+ Guide to Networks, 4E