1. technology and computing
2. hardware
3. computer networking
4. router

Chapter Overview


Identifying Network Components
Troubleshooting a Network
1
Locating Ports



The ports on a typical computer are located
either on the motherboard or on expansion
cards that plug into the system bus.
If the same type of port can have more than
one function, you can sometimes tell what a
port does by where it is located.
The locations of the motherboard ports vary,
depending on the design of the computer.
2
The Back Panel of an Older Computer
3
The Back Panel of a Newer Computer
4
DB-9 Serial Ports
5
DB-9 and DB-25 Serial Ports on an
Older Computer
6
The Female DB-25 Connector Used
by a Parallel Port
7
A 15-Pin VGA Connector
8
Six-Pin Mini-DIN Connectors
9
A Five-Pin DIN Connector
10
Universal Serial Bus (USB) Ports


The USB is a relatively recent innovation that
is replacing many of the ports on computers,
such as the serial, parallel, keyboard, and
mouse ports.
The USB is a multipurpose bus that



Runs at up to 12 megabits per second (Mbps)
Supports a wide range of devices through the
same interface
Computers today typically have two USB
ports, which use rectangular, female,
fourconductor connectors.
11
USB A-Connectors
12
SCSI Ports


The Small Computer System Interface (SCSI) is a
mass storage interface that supports many different
internal and external devices at speeds up to 160
Mbps.
SCSI implementations typically involve a host adapter
card that plugs into the computer's expansion bus.


A few computers have a SCSI adapter integrated into the
motherboard.
A SCSI host adapter usually has both internal and
external connectors.


Internally, SCSI uses ribbon connectors that attach to hard
drives and other devices.
External SCSI cables are thick and relatively inflexible
because of their heavy shielding and the tight bundling of
wires contained inside.
13
SCSI Connectors
14
A Combination Ethernet NIC
15
A BNC Connector with a T Attached
16
An Ethernet NIC with an RJ-45 Jack
17
A Token Ring Media Filter
18
The Back of a 10Base-T/100Base-TX
Ethernet Hub
19
Hubs





A hub can be either a stand-alone box or a unit that
mounts into a standard 19-inch-wide rack used for
large network installations.
Hubs can support any one of several data-link layer
protocols, including Ethernet, Fiber Distributed Data
Interface (FDDI), and Token Ring.
A hub can have as few as 4 ports or as many as 24.
The basic identifying feature of a hub is one or more
rows of female connectors.
In most cases, a hub has rows of light-emitting diode
(LED) lamps that correspond to the network cable
ports.
20
The LED Display on a
10Base-T/100Base-TX Ethernet Hub
21
Switches




Switches look like hubs.
The difference between a hub and a switch is
in the internal manipulation of incoming data.
Switches are available in most of the same
configurations as hubs, ranging from small
units intended for home or small business
networks to large rack-mounted devices.
Some switches include an additional nine-pin
serial port that connects the device to a
computer with a null modem cable.
22
A Patch Panel
23
A Typical Stand-Alone Router
24
A Router Frame with Modules
Installed
25
Internal and External Print Servers
26
Uninterruptible Power Supplies
(UPSs)
27
The Back Panel of a UPS
28
Network Troubleshooting Procedure
1. Establish the symptoms.
2. Identify the affected area.
3. Establish what has changed.
4. Select the most probable cause.
5. Implement a solution.
6. Test the result.
7. Recognize the potential effects of the
solution.
8. Document the solution.
29
Establish the Symptoms


Determine exactly what is going wrong, and
note the effect of the problem on the
network.
Assign a priority to the problem.


In a large network environment, it is essential to
establish a system of priorities that dictate which
calls get addressed first.
Most often, the severity of the problem
determines who gets attention first.
30
Rules for Establishing Priorities




Shared resources take precedence over
individual resources.
Network-wide problems take precedence over
workgroup or departmental problems.
Departmental issues should be rated
according to the function of the department.
System-wide problems take precedence over
application problems.
31
Identify the Affected Area





See if the problem can be duplicated.
Network problems that you can easily duplicate
are far easier to fix, primarily because you can
easily test to see if your solution was successful.
Having the user reproduce the problem can
sometimes lead to the solution.
If the problem can be duplicated, you can start
determining the actual source of the problem.
Eliminate the elements that are not the cause, in
a logical and methodical manner.
32
Establish What Has Changed



When a computer or other network component
that used to work properly now does not work,
some change has probably occurred.
Major changes, such as the installation of new
hardware or software, are obvious possible
causes of the problem.
Tracking down the source of a networking
problem can often be a form of detective work,
and learning to "interrogate" your "suspects"
properly can be an important part of the
troubleshooting process.
33
Select the Most Probable Cause



Follow this axiom: when you hear hoofbeats,
think horses, not zebras.
When you look for possible causes of a
problem, start with the obvious first.
Work methodically and document everything
you check so that you do not duplicate your
efforts.
34
Implement a Solution


After you have isolated the problem, determine if
it is caused by hardware or software.
If it is a hardware problem, you might replace
the faulty unit or use an alternate.



Example: for a communication problem, you might
replace network cables until you find one that is faulty.
Example: if the problem is in a server, you can replace
components until you find the culprit.
If it is a software problem, you might


Use a different computer to run the application or store
the data
Reinstall the software on the offending system
35
Test the Results




After you resolve the problem, you should return to the
beginning of the process and repeat the task that
originally caused the problem.
If the problem no longer occurs, you should test the other
functions related to the changes you made to ensure that
fixing one problem has not created another.
Repeat the procedures you used to duplicate the problem
exactly, to ensure that the problem the user originally
experienced has been completely eliminated and is not
just temporarily masked.
If the problem was intermittent, it might take some time
to ascertain if your solution worked.

Check with the user several times to make sure that the problem is
not recurring.
36
Document the Solution


Begin documenting your actions as soon as the user calls for
help.
A well-organized support organization uses a system to register
each problem call as a trouble ticket that eventually contains



A support organization often operates by using tiers.




A complete record of the problem
The steps taken to isolate and resolve the problem
Calls come in to the first tier.
If the problem is complex or the first-tier technician cannot resolve
it, the call is escalated to the second tier, which is composed of
senior technicians.
If all technicians document their activities, there should be no
problem when one technician hands off the trouble ticket to
another.
Keeping careful notes prevents duplication of effort.
37
Chapter Summary

Identifying network components




Computers have a variety of ports, some of which are implemented
by the motherboard and others by expansion cards.
Computers use many different types of connectors fortheir various
interfaces, and in some cases the same connector type can provide
different functions.
SCSI host adapters can use any one of several types of connectors,
which are not interchangeable.
Troubleshooting a network



The network troubleshooting procedure involves several steps,
including identifying, duplicating, isolating, resolving, and
documenting the problem.
Isolating a network problem is a matter of eliminating hardware
and software components as possible causes.
Maintaining documentation and following a methodical
troubleshooting procedure are essential parts of maintaining a
network.
38