Network Troubleshooting

1
Chapter 13

• Network Troubleshooting

2
Introduction

• Look at
• Avoiding Potential Problems (13.1)
• Principles of Troubleshooting (13.2)
• Accessing Key Information Resources (13.3)
• Handling Common Sources of Trouble (13.4)

3
Avoiding Potential Problems

• There are two approaches to trouble shooting
• preventing potential problems through proper
  planning
• quickly fixing what fails
• The former is often referred to as trouble
  avoidance or pre-emptive troubleshooting
• The later is referred to as troubleshooting or
  damage control

4
Avoiding Potential Problems

• To be effective, both should be used in
  combination
• Be proactive in managing the environment
• Know how to effectively troubleshoot any issue
• Documentation is important
• It's a tedious job but it is imperative that you
  have proper documentation

5
Avoiding Potential Problems

• Ensure that users have ongoing access by making
  sure that if something happens you have a backup
  plan
• Identify the data that should be backed up
• Determine the backup type and schedule
• Designate someone to be responsible
• Be sure the tapes are properly labeled
• Keep a log

6
Avoiding Potential Problems

• Security policy should detail hardware and
  software along with some of these areas
• Clear paths of responsibility and user
  expectations
• Awareness of privacy issues that may arise
• A separation of duties, so that total control is
  not left in the hands of a single individual

7
Avoiding Potential Problems

• Security policy should detail hardware and
  software along with some of these areas
• Password length, duration, history, and
  complexity requirements
• A clear policy for the destruction of data
• Procedures for creating and authorizing accounts
• Incident response and disaster recovery planning
  policies

8
Avoiding Potential Problems

• The goal of security is expressed in terms of
• Confidentiality
• Integrity
• Availability
• These goals can be achieved through creating
  hardware and software standards

9
Avoiding Potential Problems

• Workstation consistency is often overlooked
• Installing unauthorized software
• Downloading infected music and movie files
• Opening an e-mail message that contain a virus
• Using weak passwords
• Not logging off the network when leaving the
  building

10
Avoiding Potential Problems

• Standards for laptops, personal digital
  assistants (PDAs), Palm Pilots, and Pocket PCs
  may be more difficult to define
• If these devices are company issued or company
  supported, they must be standardized as well
• These devices are susceptible to theft because
  they are small and valuable.
• Many times contain important information about
  the company

11
Avoiding Potential Problems

• You must also define and document standards for
  new server installations along with guidelines
  for current server configurations
• The configuration process should start with
  installing only the services necessary for the
  server to function
• Limit physical access to the server
• Use Redundant Array of Inexpensive Disk (RAID),
  uninterruptible power supply (UPS) equipment, and
  clustering

12
Avoiding Potential Problems

• Policies should include provisions for change
  authorization, documentation, and notification
• Include procedures to be used when hardware,
  software, or storage media is replaced or
  discarded
• Planning and testing can eliminate corruption or
  data deletion problems
• Sufficient time must be spent to ensure that the
  transition goes as smoothly as possible

13
Avoiding Potential Problems

• The following should be considered when creating
  a change in management policy
• Establish a schedule for changes
• Make sure users are notified of the changes
• Conduct proper testing
• Changes should be scheduled during off hours

14
Avoiding Potential Problems

• Documentation is critical
• Before actually deploying the change, testing
  should be conducted
• Testing should be well documented
• A rollback strategy should be part of every
  change plan

15
Avoiding Potential Problems

• Thorough documentation is a necessary part of an
  administrator's job
• Document everything you do and be as detailed as
  you can
• Documenting is particularly important because of
  the impact it can have on business if legal
  action is involved
• All documents should be kept in both hard- and
  soft-copy form

16
Avoiding Potential Problems

• Your network documentation should include these
  components
• Policies and procedures
• Network history
• Network map
• Cable diagrams and layouts
• Contact list
• Equipment list

17
Avoiding Potential Problems

• Your network documentation should include these
  components
• Computer and network device configuration
• Software and its configuration
• Network address list
• Software licensing information

18
Avoiding Potential Problems

• Pre-emptive troubleshooting is also called
  trouble avoidance
• It will save time and may help save data when
  problems arise
• Pre-emptive troubleshooting can also prevent
  additional expense and downtime while trying to
  figure out what happened after a failure

19
Avoiding Potential Problems

• The ISO defines five pre-emptive troubleshooting
  network management categories
• Accounting management
• Configuration management
• Fault management
• Performance management
• Security management

20
Avoiding Potential Problems

• The measure of normal network activity is known
  as a baseline
• This gives you a point of reference when the
  network goes awry
• Baselining should be done for both network and
  application processes
• The allows you to determine whether you have a
  hardware or software issue

21
Avoiding Potential Problems

• There are tools can be used to gather network
  information
• Event Viewer allows you to audit certain events
• Task manager can be used to end processes or
  applications that get hung up without having to
  reboot the machine
• Auditing is the process of tracking users and
  their actions on the network

22
Avoiding Potential Problems

• Keep in mind that auditing uses system resources
  and space
• The Performance console is used for tracking and
  viewing the utilization of operating system
  resources
• A network monitor can be used to capture network
  traffic and generate statistics for creating
  reports

23
Principles of Troubleshooting

• Troubleshooting requires skill
• These skills are acquired through experimentation
  and experience
• You cannot learn the resolution to every problem
  that exists
• You can, however, learn a methodology to find and
  diagnose nearly every problem in a systematic and
  logical manner

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Principles of Troubleshooting

• The following are the most common network
  problems
• User error
• Physical connections
• System needs a reboot
• If these steps don't help, then it's time to move
  on and try other troubleshooting options

25
Principles of Troubleshooting

• Research on problem solving and reasoning is
  fundamental to understanding troubleshooting
  skills
• You can choose from several different
  methodologies of troubleshooting
• These give us guidelines for logical solving
  problems using a step-by-step process

26
Principles of Troubleshooting

• The first step is to determine the scope of the
  problem by identifying the symptoms
• The next step is to collect specific information
  about the problem at hand
• Once you have the pertinent information, then the
  scope is determined
• Begin to isolate the problem by testing each of
  the causes, starting with the most obvious first

27
Principles of Troubleshooting

• Attempt to re-create the problem
• Make only one change at a time
• Test each change
• Don't be afraid to ask for help
• Read the documentation that came with the
  hardware or software
• Don't forget about the obvious

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Principles of Troubleshooting

• Creating a Hardware Toolkit
• Crossover cable
• Hardware loopback adapter
• Tone generator
• Cable tester or cable checker
• Voltmeters
• Time domain reflectometer (TDR)
• Oscilloscope

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Principles of Troubleshooting

• Creating a Software Toolkit
• Ping
• Netstat
• Nbtstat
• Traceroute
• Network monitors
• Protocol analyzer

30
Accessing Key Information Resources

• One of the best places for troubleshooting a
  problem is the manufacturer's Web site
• Subscription services such as TechNet can be used
  to obtain a wealth of information
• Vendor-provided CDs should be one of the first
  places you go to look for information
• Look at the readme.txt file even before the
  product is installed

31
Accessing Key Information Resources

• Resource kits are another excellent source of
  information about your operating system
• Call the vendor and open up a technical support
  incident to solve the problem
• If it is a known issue the vendor may have
  documented fixes available

32
Accessing Key Information Resources

• Have the following information ready to assist
  the support department
• The operating system you are running
• Service packs that are installed
• Version numbers of hardware and software
• Serial numbers
• Detailed account of the problem and
  troubleshooting steps you have taken

33
Accessing Key Information Resources

• Other excellent sources of information are
  periodicals and white papers
• Many new magazines and periodicals are introduced
  each year, some of them deal with specific
  computing environments
• Besides white papers and periodicals, dont
  forget to keep a couple of good reference books
  handy, especially when you first start out

34
Handling Common Sources of Trouble

• Not all problems will be easy to fix
• The two most common causes for data not moving
  reliably are
• A physical connection breaks such as the cable
  being unplugged or broken
• A network device is not working properly

35
Handling Common Sources of Trouble

• The majority of networking problems occur at the
  Physical layer of the OSI model and include
  problems with
• cables
• connectors
• NICs
• Check cabling and connections first during your
  network troubleshooting process

36
Handling Common Sources of Trouble

• Power problems will crop up in various ways
• One of the most obvious is when power strips are
  daisy chained together
• The devices will not get enough power
• The other end of the spectrum is that this will
  occasionally trip the circuit breakers or start a
  fire

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Handling Common Sources of Trouble

• Power not properly conditioned, can have
  devastating effects on equipment
• Noise
• Spikes
• Surges and overvoltages
• Sags and brownouts
• Blackouts

38
Handling Common Sources of Trouble

• Always connect your sensitive electronic
  equipment to
• power conditioners
• surge protectors
• for the best protection an uninterruptible power
  supply (UPS)
• The UPS powers the computer so that you can take
  action without data loss

39
Handling Common Sources of Trouble

• There are basically three different types of
  devices that are classified as UPSs
• Standby power supply (SPS)
• Hybrid or ferroresonant UPS systems
• Continuous UPS
• Never plug a printer into a UPS
• Power problems cannot be eliminated but the
  damage can be minimized or prevented

40
Handling Common Sources of Trouble

• A software upgrade can cause issues on the system
  even though you tested the upgrade
• You should be prepared to rollback or reverse the
  process.
• This process is also referred to as backleveling
• Most often the best source of help when a problem
  occurs is the manufacturer's documentation

41
Handling Common Sources of Trouble

• You will also have to provide for a backup plan
  in the event a hardware upgrade doesn't go as
  planned
• It is important not the discard the old device in
  the event the upgrade causes issues
• This applies to the drivers that may be necessary
  as well

42
Handling Common Sources of Trouble

• The complexity of network topology and
  communication equipment has become more and more
  sophisticated
• Performance management as well as response time
  management is more difficult
• Sometimes you will find that for an unknown
  reason the network performance begins to suffer

43
Handling Common Sources of Trouble

• Here are some avenues for you to consider when
  there are issues with performance
• Change is the biggest factor that can cause poor
  network performance
• Another big factor that affects network
  performance is playing games or downloading music
  and movie files

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Handling Common Sources of Trouble

• Here are some avenues for you to consider when
  there are issues with performance
• Sometimes applications have memory leaks or a new
  version may be bloated or have an improperly
  programmed query function
• Adding new electrical equipment may have a
  negative effect on the network

45
Handling Common Sources of Trouble

• Here are some avenues for you to consider when
  there are issues with performance
• Adding new hardware such as additional servers or
  workstations may cause performance to decrease
• Other changes in workload or workplace behavior,
  including adding more users, could affect
  performance