with the physical layer at the user-site can be
eliminated. Effective questioning techniques can discover this
type of information without requiring a trip to the end-user
location. The commands shown in the figure can be used to check
the status of various devices and be used to determine which
configuration aspects to inspect. The troubleshooter should use
effective questioning techniques to document the symptoms of a
problem: - Ask questions that are pertinent to the
problem.
- Use each question as a means to either
eliminate or discover possible problems.
- Speak at a
technical level that the user can understand.
- Ask the
user when the problem was first noticed.
- Ask the user
to re-create the problem, if possible.
- Determine the
sequence of events that took place before the problem happened.
- Match the symptoms that the user describes with
common problem causes.
Content
2.3 Gathering Symptoms 2.3.4
Questions to ask an end-user When asking an end user
questions, it is important to follow a specific sequence to
allow the troubleshooter to gain the knowledge necessary to
attain a solution. A typical format for interviewing an end
user concerning their problem is: - What does not work?
- What does work?
- Are the things that do and
do not work related?
- Has the thing that does not work
ever worked?
- When the problem was first noticed?
- What has changed since the last time it did work?
- Did anything unusual happen since the last time it
worked?
- When exactly does the problem occur?
- Can the problem be reproduced and if so, how can it be
reproduced?
Content 2.3
Gathering Symptoms 2.3.5 Flow charts for
gathering network and end-user symptoms Stage 1
Interview user – If possible, a troubleshooter gathers
initial symptoms from the user and uses these symptoms as a
basis for additional troubleshooting. Stage 2 Analyze
symptoms – A troubleshooter will get a description of the
problem by analyzing any gathered symptoms from the user
Stage 3 Determine symptoms – Using a layered
troubleshooting approach, a troubleshooter gathers hardware and
software symptoms from the end system starting with the most
likely cause. The troubleshooter should rely on previous
experience, if possible, to decide if the problem is more
likely a hardware or software problem. Stage 4 Document
symptoms – Document any hardware and software symptoms. If
the problem can be solved using the documented symptoms, a
troubleshooter solves the problem and documents the solution.
If the problem cannot be solved at this point, then the
isolating phase of the general troubleshooting process is
initiated. Lab Activity Lab Exercise: Gathering
Symptoms After completing this lab, the student will be able to
decide what questions to ask and which troubleshooting tools to
use to completely document the symptoms of a network problem.
Content 2.4 Network Management Tools
2.4.1 Network management system frameworks Network
management can range from a solitary network consultant
monitoring network activity with a simple protocol analyzer, to
the use of a distributed database with auto-polling of network
devices. Network management could even include the use of high
end workstations generating real time graphical views of
network topology changes and traffic. In general, network
management is a service that employs a variety of tools,
applications, and devices to assist network managers in
monitoring and maintaining networks. Most network management
architectures use the same basic structure and set of
relationships. End stations, or managed devices, such as
computer systems and other network devices, run software that
enables them to send alerts when they recognize problems. An
example would be when one or more user determined thresholds
are exceeded. Upon receiving these alerts, management entities
are programmed to react by executing one action, or a group of
actions. This would include operator notification, event
logging, system shutdown, or automatic attempts at system
repair. Management entities can also poll end stations to check
the values of certain variables. Polling can be automatic or
user initiated, but agents in the managed devices respond to
all polls. Agents are software modules that first compile
information about the managed devices in which they reside, and
then store this information in a management database. Finally
agents provide information proactively or reactively to
management entities within network management systems (NMSs)
via a network management protocol. Well known network
management protocols include the Simple Network Management
Protocol (SNMP) and Common Management Information Protocol
(CMIP). Management proxies are entities that provide management
information on behalf of other entities. Figure depicts a
common network management architecture. The International
Organization for Standardization (ISO) has contributed a great
deal to network standardization. The organization's network
management model is the primary means for understanding the
major functions of NMSs. This model consists of five conceptual
areas: - Performance management – The goal is to
measure and provide various aspects of network performance in
order to maintain internetwork performance at an acceptable
level. Examples of performance variables include network
throughput, user response times, and line utilization.
- Configuration management – The goal is to monitor
network and system configuration information so that the
effects on network operation of various versions of hardware
and software elements can be tracked and managed.
- Accounting management – The goal is to measure
network-utilization parameters so that individual or group use
of the network can be regulated appropriately. Such regulation
minimizes network problems because network resources can be
apportioned based on resource capacities, and maximizes the
fairness of network access among users.
- Fault
management – The goal is to detect, log, notify users of,
and if possible, automatically fix network problems to keep the
network running effectively. Because faults can cause downtime
or unacceptable network degradation, fault management is
perhaps the most widely implemented of the ISO network
management elements.
- Security management – The
goal is to control access to network resources to prevent the
network from being sabotaged or unintentionally brought down,
and to prevent sensitive information from being accessed by
unauthorized users. A security management subsystem can monitor
users logging on to a network resource and deny access to those
who enter inappropriate access codes.
Content
2.4 Network Management Tools 2.4.2
Knowledge base tools Knowledge bases represent an
invaluable tool for the network troubleshooter. The most
visible example of a knowledge base is the Internet. It has
become a very valuable tool for many individuals seeking
answers on specific problems. It potentially represents a vast
pool of experience based information. A knowledge base is
often a database collection of empirical information on a
specific technical area. It consists of real solutions to
problems encountered on a single or on numerous occasions. The
art in knowledge base tools is in the identification of
keywords or phrases that are associated with particular
problems and problem areas. With highly developed Internet
search engines, standardized methods for cataloging information
mean that it is relatively easy to present a knowledge base in
a user-friendly web browser format. The Cisco Systems website
reached at http://www.cisco.com/ incorporates a free knowledge
base tool on Cisco related hardware and software. This site
represents an invaluable troubleshooting resource for Cisco
customers, support staff, and design personnel. It contains