Download Guide to Networking Essentials, Fifth Edition

Guide to Networking Essentials, Fifth Edition
Chapter 14
Solving Network Problems
At a Glance
Instructor’s Manual Table of Contents

Overview

Objectives

Teaching Tips

Quick Quizzes

Class Discussion Topics

Additional Projects

Additional Resources

Key Terms

Technical Notes for Hands-On Projects
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Lecture Notes
Overview
Chapter 14 offers an introduction to solving network problems. Students learn about the
benefits of network management and planning. They also learn about different
approaches to network troubleshooting, and the steps involved in the problem-solving
process. Students also learn about the types of specialized equipment and other
resources for troubleshooting. Finally, they learn about some measures that can be taken
in common troubleshooting situations.
Objectives
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


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Describe the benefits of network management and planning
Explain different approaches to network troubleshooting
List the steps of the problem-solving process
Explain the types of specialized equipment and other resources for troubleshooting
Describe some measures to take in common troubleshooting situations
Teaching Tips
Preventing Problems with Planning and Documentation
1. Explain that you should solve network problems in two ways: preventing problems
through planning and management (called preemptive troubleshooting), and repairing
and controlling existing damage (called troubleshooting).
2. Explain that network management and troubleshooting should combine to form an
overall network plan.
Backing Up Network Data
1. Describe the guidelines that should be followed to formulate any backup plan.
Setting Hardware and Software Standards
1. Explain why to make hardware and software easier to manage, network components
should follow established standards. Provide some tips on how to define these
standards.
2. Stress that you should evaluate standards often—ideally, once per quarter.
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Establishing Upgrade Guidelines
1. Explain that as an extension of hardware and software standards, you should also
establish guidelines for upgrades.
2. Explain that you should give your users advanced notice so that they know changes will
take place. Stress that disruptive upgrades shouldn’t be carried out during normal
working hours. Note that it is a good idea to “pilot” new upgrades with technically
astute users.
3. Stress that you should always formulate a rollback plan.
Maintaining Documentation
1. Briefly describe each of the documents that should be included in any network plan.
Performing Preemptive Troubleshooting
1. Explain that preemptive troubleshooting is costly but saves time when problems do
come up, prevents equipment problems, and ensures data security.
2. Briefly describe the five preemptive troubleshooting network management categories
identified by the ISO.
Practicing Good Customer-Relation Skills
1. Explain the importance of practicing good customer-relation skills. Stress that
technically adept users are an excellent source of troubleshooting information.
2. Note that all IT Departments should have guidelines that instruct personnel how to
interact with users. These guidelines should include what questions to ask users, how to
respond to irate users, how to respond to user questions, and how to follow general user
communication etiquette guidelines.
Using Network-Monitoring Utilities
1. Explain the importance of using network-monitoring utilities, in particular, to learn
which statistics to monitor, and to collect data over time to establish a baseline.
2. Explain that network-monitoring utilities gather the following types of information
(briefly describe each): events, system use statistics, and system performance statistics.
3. Explain that the information gathered using these tools can help:
 Identify network devices that create bottlenecks
 Provide information for forecasting growth and planning capacity requirements
 Develop plans to improve network performance
 Monitor events caused by software or hardware changes
 Monitor trends in network traffic and utilization
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4. Briefly describe the role of the Windows Performance Monitor.
5. Creating a Network Baseline. Explain that a baseline is helpful for identifying daily
network utilization patterns, possible bottlenecks, heavy use patterns, and protocol
traffic patterns. Note that using Performance Monitor and a baseline, you can often
avoid potential network problems. Stress that baselines should be taken periodically,
and established over periods when no problems are evident on the network.
6. Monitoring with Simple Network Management Protocol. Provide a brief introduction to
TCP/IP’s SNMP, including how it works. Don’t forget to introduce the terms software
agent and MIB. Note that you can set thresholds for generating alert messages.
Teaching
Tip
For more information on SNMP, visit:
www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/snmp.htm and
http://en.wikipedia.org/wiki/Simple_network_management_protocol.
7. Using Remote Monitoring for Advanced Monitoring. Provide a brief introduction to
RMON. Briefly describe the two versions: RMON1 and RMON2. Note how RMON
differs from and complements SNMP.
Teaching
Tip
For more information on RMON, visit:
www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/rmon.htm and
www.tcpipguide.com/free/t_TCPIPRemoteNetworkMonitoringRMON.htm.
Quick Quiz 1
1. SNMP defines a single MIB type to collect network data, but RMON1 defines
____________________ additional MIB types, called RMON groups, to provide a
more comprehensive set of data about network use.
Answer: nine
2. Each SNMP software agent monitors network traffic and device status and stores
information in a(n) ____________________ (MIB).
Answer: management information base
3. A(n) ____________________ plan is a plan to undo an installation.
Answer: rollback
4. What is a network baseline?
Answer: A network baseline is a point of reference for measuring network performance
and behavior when problems occur.
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Approaches to Network Troubleshooting
1. Explain that tackling different problems requires different approaches. In this section,
students learn about different methods and circumstances in which some methods work
and others do not.
Trial and Error
1. Stress that the trial-and-error approach to network problem solving is not very
scientific, and technical purists often frown on it.
2. Describe the conditions under which this approach can be used. Describe the conditions
under which this approach should not be used.
3. Briefly discuss the guidelines that should be followed when using the trial-and-error
approach.
4. Use one or more examples to help students understand how to determine under which
circumstances this troubleshooting method is appropriate.
Solve by Example
1. Explain how the solve by example approach works. Stress that it is easy and fast
because it requires no special knowledge or problem-solving skills.
2. Describe the general rules that should be followed when using this approach.
3. Use one or more examples to illustrate the solve by example process.
The Replacement Method
1. Explain why the replacement method is a favorite among PC technicians.
2. List the rules that should be followed when using the replacement method.
Step by Step with the OSI Model
1. Use Figure 14-1 to illustrate how the step by step with the OSI model approach works.
2. Note that this method of problem solving is what most people think of as network
support.
3. Note that some network technicians prefer to start at the Application layer while others
prefer to start at the Physical layer. Stress that the approach taken depends on your
experience and information you have learned from interviewing users. What’s
important is that you understand everything required for the network connection to
work, which allows you to test and check all components involved with the tools
available to you.
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The Problem-Solving Process
1. Use Figure 14-2 to introduce the problem-solving process.
Step 1: Determine the Problem Definition and Scope
1. Discuss the questions that should be asked to determine the problem definition and
scope.
Step 2: Gather Information
1. Explain each of the questions that should be asked to users to gather information about
the problem being solved:
a. Did it ever work?
b. When did it stop working?
c. Has anything changed?
d. Never ignore the obvious.
e. Define how it’s supposed to work.
Step 3: Consider Possible Causes
1. Explain that experience is invaluable in this step. Note that the goal in this step is to
create a checklist of possible things that could have gone wrong to cause the problem.
Step 4: Devise a Solution
1. Briefly discuss the issues that should be considered before devising a solution.
2. Note that before you implement the solution, you must be prepared for the possibility
that it could make things worse than the existing problem.
3. Explain that depending on the scope of the problem and solution, you might need to do
the following:
 Save all network device configuration files
 Document and back up workstation configurations
 Document wiring closet configurations, including device locations and patch cable
connections
 Conduct a final baseline to compare new and old results if a rollback becomes
necessary
Step 5: Implement the Solution
1. Explain that in step 5 you:
a. Create Intermediate Testing Opportunities. Stress that you should design the
implementation so that you can stop and test it at critical points.
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b. Inform your Users. Note that you should inform users of your intentions, and
give them plenty of time to schedule downtime of the network.
c. Put the Plan Into Action. Stress that you should take notes about every change
you make to the network or servers.
Teaching
Tip
Stress that making only one testable change at a time is crucial.
Step 6: Test the Solution
1. Use one or more examples to explain that testing should attempt to emulate a real-world
situation as closely as possible.
Step 7: Document the Solution
1. Explain that after solving the problem, you must take the notes made during the
implementation and testing steps and turn them into a cohesive document.
2. Note that the documentation should include everything pertinent to the problem, such as
the problem definition, the solution, the implementation, and the testing. Explain that
including this information in your overall network plan may be advisable.
Step 8: Devise Preventive Measures
1. Explain that after you have solved a problem and documented it, you should do
everything you can to prevent that problem or similar problems from recurring.
2. Note that devising preventive measures is proactive rather than reactive network
management.
Quick Quiz 2
1. What is the solve by example problem-solving process?
Answer: The solve by example problem-solving process consists of comparing
something that doesn’t work with something that does, and then making modifications
to the nonfunctioning item until it performs like the functioning one.
2. The ____________________ approach to network problem solving is not very
scientific, and technical purists often frown on it.
Answer: trial-and-error
3. The ____________________ approach to network problem solving is what most people
think of as network support.
Answer: step by step with the OSI model
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4. What is the replacement method approach to network problem solving?
Answer: The replacement method approach to network problem solving requires
narrowing down possible sources of the problem and having known working
replacement parts on hand so that they can be swapped out.
Making Use of Problem-Solving Tools
1. This section covers tools available for troubleshooting, monitoring, and documenting
your network.
Experience
1. Explain that:
a. You should make the most of your experience. Stress the importance of keeping
a journal of your experiences.
Teaching
Tip
Note that an electronic journal is helpful because you can file your entries
alphabetically and search for them when needed. Of course, a printout is also
useful when your network crashes and electronic documentation is unavailable.
b. If it happened once, it will happen again. Explain that due to standardized
hardware and software, obscure-looking problems will likely show up again.
c. Colleague’s experience. Note that to facilitate contacting colleagues, you may
put them on an e-mail distribution list.
d. Experience from manufacturer’s technical support. Explain that the best time to
call technical support is when you have a specific error number or message that
you can report to the manufacturer.
The World Wide Web
1. Describe the importance of each of the following useful Web resources:
a. Using a knowledge base. Note that when consulting manufacturers’ knowledge
bases and FAQs, you should be as specific as possible.
b. Finding Drivers and Updates. Stress that you should read the installation guide
or Readme.txt file before installing OS updates.
c. Consulting Online Support Services and Newsgroups. For example, Experts
Exchange (www.experts-exchange.com).
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d. Researching Online Periodicals. For example, LAN Magazine, eWeek, Network
Computing, etc.
Network Documentation
1. Explain that good network documentation can mean the difference between a fiveminute fix and hours, or even days, of troubleshooting.
Teaching
Tip
For more information on network documentation, visit:
www.networkdocumentation.com/.
2. Stress that you should document everything that’s important to installing, maintaining,
and troubleshooting the network.
3. Network Topology. Stress the importance of documenting the network topology.
Explain that the documentation should include a network diagram showing the logical
topology (for an example, see Figure 14-3) and another diagram showing the physical
aspects of your network (see Figure 14-4).
4. Internetworking Devices. Explain that internetworking devices require different levels
of documentation, depending on the type of equipment. Use Table 14-1 to explain that
besides including the devices in the network topology documents, you should list them
in tabular form.
Additional Tools for Network Troubleshooting
1. Explain that sometimes, your own network is the only place you can get the information
you need.
2. Note that many networking problems occur at lower layers of the OSI model, where
they are often difficult to troubleshoot. Fortunately, there are tools for diagnosing these
problems.
3. Digital Voltmeter (DVM). Explain that a DVM measures a cable’s resistance and
determines whether a cable break occurred, and that it can be used to identify short
circuits.
Teaching
Tip
More on voltmeters at: http://en.wikipedia.org/wiki/Voltmeter.
4. Time-Domain Reflectometer (TDR). Explain that a TDR measures the time it takes for a
signal to return and estimates how far down the cable the fault is located. Note that a
high-quality TDR can determine the location of a break within a few inches, and that
there are TDRs available for fiber-optic cables as well. Stress that you should use a
TDR to document actual lengths of all cables.
Guide to Networking Essentials, Fifth Edition
Teaching
Tip
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More on TDRs at: http://en.wikipedia.org/wiki/Time-domain_reflectometer.
5. Basic Cable Testers. Explain that basic cable testers are excellent tools for checking
patch cables and testing for correct termination of a cable at the patch panel and jack.
Note that these tools can’t check a cable for attenuation, noise, or other possible
performance problems in your cable run.
6. Advanced Cable Testers. Explain that advanced cable testers not only measure where a
break is located in a cable, but can also gather other information, including a cable’s
impedance, resistance, and attenuation characteristics. Stress that they function at both
layers 1 and 2 of the OSI model, and that they combine the characteristics of a DVM, a
TDR, and a protocol analyzer.
7. Oscilloscopes. Explain that oscilloscopes are advanced pieces of electronic equipment
that measure signal voltage over time. Note that when used with a TDR, an oscilloscope
can help identify shorts, sharp bends or crimps in a cable, cable breaks, and attenuation
problems.
Teaching
Tip
More on oscilloscopes at: http://en.wikipedia.org/wiki/Oscilloscope.
8. Network Monitors. Explain that network monitors are software packages that can track
all or part of the network traffic. Note that by examining the packets sent across the
network, they can track information such as packet type, errors, and traffic. List some
examples of network monitors.
9. Protocol Analyzers. Describe how protocol analyzers work. Note that some combine
hardware and software in a self-contained unit. List (and briefly describe) some
examples of protocol analyzers. Explain that experienced network administrators rely
on protocol analyzers to establish baselines for network performance and to
troubleshoot their networks.
Common Troubleshooting Situations
1. This section outlines some common network problems and possible solutions.
Cabling and Related Components
1. Explain that since the majority of networking problems occur at the Physical layer, you
should first determine whether the problem lies with the cable or the computer. Provide
some tips on how to do this.
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Power Fluctuations
1. Explain that power fluctuations in a building can adversely affect computers. Provide
some tips on how to deal with power fluctuations.
Upgrades
1. Explain that when you perform network upgrades, you should remember three
important points.
 Ignoring upgrades to new software releases and new hardware can lead to a
situation in which a complete network overhaul is necessary because many upgrades
build on top of others.
 Test any upgrade before deploying it on your production network.
 Don’t forget to tell users about upgrades.
Poor Network Performance
1. Describe the questions that should be asked to help pinpoint the causes of reduced
network performance.
Quick Quiz 3
1. What is a DVM used for?
Answer: A DVM measures a cable’s resistance and determines whether a cable break
occurred.
2. What can a TDR be used for?
Answer: A TDR can pinpoint how far from the device the break is located by sending
an electrical pulse down the cable that reflects back when it encounters a break or short.
3. ____________________ is a popular free protocol analyzer that is available for both
Windows and Linux/UNIX environments.
Answer: Ethereal
4. Most manufacturers store their technical support problems and solutions in a database
called a knowledge base or a(n) ____________________ (FAQ) document.
Answer: frequently asked questions
Class Discussion Topics
1. Ask students to describe in class the process they usually follow to solve a problem on
their personal computers or home networks.
2. Are students accustomed to using the Web to help them solve their network or computer
problems? If so, ask them to list some of the Web sites they usually visit to find help or
tips during the troubleshooting process.
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Additional Projects
1. Ask students to compile a list of free protocol analyzers. The list should include the
name, URL, and a brief description of each tool.
2. Ask students to do some research on the history and evolution of SNMP and RMON.
They should write a one-page report of their findings.
Additional Resources
1. Windows XP Network Troubleshooting:
www.practicallynetworked.com/sharing/troubleshoot/
2. Network Troubleshooting:
http://compnetworking.about.com/cs/troubleshooting/
3. Troubleshooting TCP/IP Networks:
www.onecomputerguy.com/networking/trouble.htm
4. Creating a Data Backup Plan:
http://techrepublic.com.com/1200-26-5124062.html
5. Simple Network Management Protocol (SNMP):
www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/snmp.htm
6. Simple Network Management Protocol:
http://en.wikipedia.org/wiki/Simple_network_management_protocol
7. Remote Monitoring (RMON):
www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/rmon.htm
8. TCP/IP Remote Network Monitoring (RMON):
www.tcpipguide.com/free/t_TCPIPRemoteNetworkMonitoringRMON.htm
9. Creating Accurate Network Documentation:
http://techrepublic.com.com/1200-26-5123756.html
10. Network Documentation:
www.networkdocumentation.com/
11. Network Documentation Policy:
www.comptechdoc.org/independent/security/policies/network-documentationpolicy.html
12. Network Troubleshooting:
www.comptechdoc.org/independent/networking/guide/nettrouble.html
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13. Voltmeter:
http://en.wikipedia.org/wiki/Voltmeter
14. Time-Domain Reflectometer:
http://en.wikipedia.org/wiki/Time-domain_reflectometer
15. Oscilloscope:
http://en.wikipedia.org/wiki/Oscilloscope
Key Terms
 cable testers — Network troubleshooting devices that can test for cable defects,
monitor network collisions, and monitor network congestion.
 digital voltmeter (DVM) — A network troubleshooting tool that measures voltage,
amperage, and resistance on a cable or other conductive element.
 frequently asked questions (FAQ) — A Web document with two parts to each entry.
The first part is a question the manufacturer has anticipated or received from customers;
the second part is an answer to that question.
 management information base (MIB) — A set of objects containing information
about a networking device that SNMP uses to manage that device.
 network monitors — Software that monitors network traffic and gathers information
about packet types, errors, and packet traffic to and from each computer.
 oscilloscopes — Network troubleshooting devices that measure the signal voltage per
amount of time. When used with a TDR, they can help define cable problems. See also
time-domain reflectometer (TDR).
 preemptive troubleshooting — A method of forestalling network problems by
planning in advance and performing regular network maintenance.
 Remote Monitoring (RMON) — Specialized software that gathers network data and
provides statistics to a network management console.
 rollback plan — Part of an upgrade plan that provides instructions on how to undo the
upgrade if problems happen during the upgrade.
 short circuit — A condition that occurs when conductors that are normally insulated
from one another establish a connection. In a coaxial cable, if the shield and the internal
conductor become connected, the cable stops functioning because the short circuit
blocks all network traffic; the same condition can occur in twisted-pair cable if two or
more of the paired wires become connected.
 software agents — Part of the SNMP structure loaded onto each device to be
monitored.
 time-domain reflectometer (TDR) — A network troubleshooting device that can
determine whether there’s a break or short in the cable and, if so, approximately how far
down the cable it’s located.
 troubleshooting — The process of detecting problems, identifying causes or
contributing factors, and applying necessary workarounds or repairs to eliminate their
effects.
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Technical Notes for Hands-On Projects
Hands-On Project 14-1: In this project, students use their current network documentation.
Hands-On Project 14-2: In this project, students install Network Monitor on Windows Server
2003.
Hands-On Project 14-3: In this project, students use Network Monitor on Windows Server
2003.
Hands-On Project 14-4: In this project, students install SNMP support on Windows Server
2003 (Start  Control Panel  Network Connections).
Hands-On Project 14-5: In this project, students use the ipconfig, ping, tracert, and print
command-line Windows XP utilities.
Hands-On Project 14-6: This project requires a Web browser and Internet access. Students
download and install Ethereal.
Hands-On Project 14-7: In this project, students use Ethereal (installed in Project 14-6).