3/8/2016

UNIT 5
NETWORK
TROUBLESHOOTING
Prepared by : Zuraiti Bt Che Amat

Understand the basic troubleshooting

methodology

Prepared by : Zuraiti Bt Che Amat

1
 3/8/2016

Outcomes 1 :
At the end of this subtopic, student should be able to:
5.1.1 Five (5) technique
5.1.2 Six (6) steps involved in the basic
troubleshooting methodology
5.1.3 Assess common physical problems in network.

Prepared by : Zuraiti Bt Che Amat

Troubleshooting ?
 Troubleshooting is the process of identifying,
locating and correcting problems that occur.
 Experienced individuals often rely on instinct to
troubleshoot.
 When a problem is reported, verify it and
determine the extent. Once the problem is
confirmed, the first step in troubleshooting is to
gather information.

Prepared by : Zuraiti Bt Che Amat

2
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

 There are several different structured

troubleshooting techniques available, including:
Top-down
Bottom-up
Divide-and-conquer
 They may use less structured techniques such as
trial and error
substitution.

Prepared by : Zuraiti Bt Che Amat

3
 3/8/2016

5 troubleshooting techniques

1 Top-down
2 Bottom-up
3 Divide-and-conquer
4 Trial and error
5 Substitution
Prepared by : Zuraiti Bt Che Amat

Top-down approach
 Top-down starts with the application layer and
works down.
 It looks at the problem from the point of view of
the user and the application.
 Is it just one application that is not functioning, or
do all applications fail? For example, can the user
access various web pages on the Internet, but not
email? Do other workstations have similar issues?

Prepared by : Zuraiti Bt Che Amat

4
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Divide-and-Conquer approach
 Divide-and-Conquer typically begins
troubleshooting at one of the middle layers and
works up or down from there.
 For example, the troubleshooter may begin at the
network layer, by verifying IP configuration
information.

Prepared by : Zuraiti Bt Che Amat

5
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Bottom-up approach
 Bottom-up starts with the physical layer and
works up.
 The physical layer is concerned with hardware
and wire connections.
 Have cables been pulled out of their sockets? If
the equipment has indicator lights, are they on or
off?

Prepared by : Zuraiti Bt Che Amat

6
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

7
 3/8/2016

Trial and Error

 Trial and error relies on individual knowledge to
determine the most probable cause of a problem.
 A troubleshooter makes an educated guess on the most
likely solution based on past experience and knowledge of
the network structure.
 Once the solution is implemented, if it does not work, the
troubleshooter uses this information to help determine the
next most likely cause.
 This process is repeated until the problem is isolated and
solved.
 While the trial and error approach has the potential to be
extremely fast, it relies on the abilities and experiences of
the troubleshooter and can result in incorrect assumptions
and overlooking simple solutions.
Prepared by : Zuraiti Bt Che Amat

Substitution
 With this technique the problem is assumed to be caused
by a specific hardware component or a configuration file.
 The defective part or code is replaced by a known good
device or file.
 While not necessarily locating the problem, this technique
can save time and quickly restore network functionality.
 This relies on the availability of substitute parts,
components, and backup configuration files which can be
very expensive to maintain.
 An example of a substitution technique is when an ISP
replaces a possible broken device rather than send a
technician out to troubleshoot and locate a specific issue.
This technique is also often used for inexpensive parts such
as replacing network interface cards and patch cables.
Prepared by : Zuraiti Bt Che Amat

8
 3/8/2016

Identify the troubleshooting technique used in

the given scenario.

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

9
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

10
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Activity 4

11
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

12
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

13
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Troubleshooting
Methodology

Prepared by : Zuraiti Bt Che Amat

14
 3/8/2016

Basic Troubleshooting Methodology

a. Identify the symptoms and potential causes
b. Identify the affected area
c. Establish what has changed (hardware, software etc.)
d. Implement an action plan and solution
e. Test the result
f. Document the solution

Prepared by : Zuraiti Bt Che Amat

A. Identify the symptoms and potential causes

 When troubleshooting errors involving an
individual user and workstation, in step 1, you’ll
need to find out what steps the user is following
when the error takes place.
 This will not only show you whether the user is
causing the problem inadvertently, it will also
show you how to re-create the problem and what
components are involved in the user’s process.

Prepared by : Zuraiti Bt Che Amat

15
 3/8/2016

B. Identify the affected area

 In step 2, you need to verify what area is affected.
Are other users experiencing the same problem?
Is this problem limited to a certain application? A
workstation? Does the problem follow the user
around the network if the process is tried at a
different station?

Prepared by : Zuraiti Bt Che Amat

C. Establish what has changed (hardware,

software etc.)
 The next course of action is to find out what has
changed since the process last worked correctly.
If it is the first time the user has tried it, you
should always consider the possibility that the
user lacks the correct rights and privileges, which
we will discuss later in this chapter.

Prepared by : Zuraiti Bt Che Amat

16
 3/8/2016

D. Implement an action plan and solution

 Step 4 instructs you to decide on a probable
cause. This will depend entirely on the
circumstances of the problem, and there might be
more than one possible cause.
 Then, you implement a solution.

Prepared by : Zuraiti Bt Che Amat

E. Test the result

 Step 5, you test it, and recognize whether the
solution was successful.
 If not, you try another solution.

Prepared by : Zuraiti Bt Che Amat

17
 3/8/2016

F. Document the solution

 Once you’ve fixed the problem, you should
document it.
 Document all steps taken in troubleshooting,
even the ones that did not solve the issue.
 This documentation becomes a valuable reference
should the same or similar problem occur again.

Prepared by : Zuraiti Bt Che Amat

Assess common
physical problems in
network.

Prepared by : Zuraiti Bt Che Amat

18
 3/8/2016

7.1.3 Assess common physical problems in

network.
 A large proportion of networking problems are related to
physical components or problems with the physical layer.
 Physical problems are concerned mainly with the hardware
aspects of computers and networking devices and the
cables that interconnect them.
 Physical problems do not consider the logical (software)
configuration of devices.
 Physical problems can occur in both wired and wireless
networks.
 One of the best detection methods for physical problems is
the use of the senses - vision, smell, touch and hearing.

Prepared by : Zuraiti Bt Che Amat

Assess common physical problems in

network.

1 • SENSE OF SIGHT

2 • SENSE OF SMELL

3 • SENSE OF TOUCH

4 • SENSE OF HEARING

Prepared by : Zuraiti Bt Che Amat

19
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

20
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

21
 3/8/2016

Self Reflection
You have learnt :
1. What is troubleshooting
2. 5 technic for troubleshooting
3. 6 troubleshooting methodology
4. 4 way to access common physical network

Are you ready for new topic???

Prepared by : Zuraiti Bt Che Amat

Software utilities for

troubleshooting
connectivity.
Prepared by : Zuraiti Bt Che Amat

22
 3/8/2016

Outcomes
At the end of subtopic, you will be able to :

1. Perform troubleshooting using ipconfig.

2. Perform troubleshooting using ping
3. Perform troubleshoot using Tracert
4. Perform troubleshooting using Netstat
5. Perform troubleshooting using Nslookup
6. Combine variety of software and hardware tools
to diagnose problems.
Prepared by : Zuraiti Bt Che Amat

ipconfig

tracert ping
SOFTWARE
UTILITIES

nslookup netstat
Prepared by : Zuraiti Bt Che Amat

23
 3/8/2016

FUNCTIONS :
ipconfig - Displays IP configuration
information
ping - Tests connections to other IP hosts
tracert - Displays route taken to destination
netstat - Displays network connections
nslookup - Directly queries the name server
for information on a destination domain

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

24
 3/8/2016

7.1.5 Perform troubleshooting using ipconfig

command.
 Ipconfig is used to display the current IP
configuration information for a host.
 Issuing this command from the command prompt
will display the basic configuration information
including: IP address, subnet mask and default
gateway.

Prepared by : Zuraiti Bt Che Amat

Examples
> ipconfig ... Show information
> ipconfig /all ... Show detailed information
> ipconfig /renew ... renew all adapters
> ipconfig /renew EL* ... renew any connection that
has its name starting with EL
> ipconfig /release *Con* ... release all matching
connections,
eg. "Local Area Connection 1" or "Local Area Connection 2"

> ipconfig /allcompartments ... Show information about

all compartments

> ipconfig /allcompartments /all ... Show detailed

information about all compartments
Prepared by : Zuraiti Bt Che Amat

25
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Ipconfig /all
 The command ipconfig /all displays additional information
including the MAC address, IP addresses of the default
gateway and the DNS servers. It also indicates if DHCP is
enabled, the DHCP server address and lease information.
 How can this utility assist in the troubleshooting process?
Without an appropriate IP configuration, a host can not
participate in communications on a network. If the host
does not know the location of the DNS servers it cannot
translate names into IP addresses.

Prepared by : Zuraiti Bt Che Amat

26
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Ipconfig /release and ipconfig /renew

 If IP addressing information is assigned dynamically, the
command ipconfig /release will release the current DHCP
bindings. Ipconfig /renew will request fresh configuration
information from the DHCP server. A host may contain faulty
or outdated IP configuration information and a simple renewal
of this information is all that is required to regain connectivity.
 If after releasing the IP configuration, the host is unable to
obtain fresh information from the DHCP server, it could be
that there is no network connectivity. Verify that the NIC has an
illuminated link light, indicating that it has a physical
connection to the network. If this does not solve the problem,
it may be an issue with the DHCP server or network
connections to the DCHP server.

Prepared by : Zuraiti Bt Che Amat

27
 3/8/2016

7.1.6 Perform troubleshooting using ping

command.

 If the IP configuration appears to be correctly

configured on the local host, next, test network
connectivity by using ping.
 Ping is used to test if a destination host is
reachable.
 The ping command can be followed by either an
IP address or the name of a destination host, as
for example:
ping 192.168.7.5
ping www.google.com
Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

28
 3/8/2016

 When a ping is sent to an IP address, a packet known as an

echo request is sent across the network to the IP address
specified.
 If the destination host receives the echo request, it
responds with a packet known as an echo reply. If the
source receives the echo reply, connectivity is verified.
 If a ping is sent to a name, such as www.cisco.com, a
packet is first sent to a DNS server to resolve the name to
an IP address.
 Once the IP address is obtained, the echo request is
forwarded to the IP address and the process proceeds. If a
ping to the IP address succeeds, but a ping to the name
does not, there is most likely a problem with DNS.
Prepared by : Zuraiti Bt Che Amat

 If pings to both the name and IP address are successful, but the
user is still unable to access the application, then the problem
most likely resides in the application on the destination host.
For example, it may be that the requested service is not
running.
 If neither ping is successful, then network connectivity along
the path to the destination is most likely the problem. If this
occurs, it is common practice to ping the default gateway. If the
ping to the default gateway is successful, the problem is not
local. If the ping to the default gateway fails, the problem
resides on the local network.
 The basic ping command usually issues four echoes and waits
for the replies to each one. It can, however, be modified to
increase its usefulness. The Options listed in the graphic display
additional features available.
Prepared by : Zuraiti Bt Che Amat

29
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

When troubleshooting PC problems

1. Determine whether the user can ping the loopback
address: ping 127.0.0.1.
If this fails, then something is wrong with the
TCP/IP stack installation on the PC.
2. Next, have the user try to ping the locally configured
IP address.
If this fails, something is wrong with the IP address
configuration on the PC.
3. Next, have the user ping the default gateway.
If this fails, then something is wrong with the
configured default gateway address, the default
gateway itself, or the subnet mask value configured
on the user’s PC.
Prepared by : Zuraiti Bt Che Amat

30
 3/8/2016

7.1.7 Perform troubleshoot using Tracert

 The ping utility can verify end-to-end connectivity.
 However, if a problem exists and the device cannot ping the destination,
the ping utility does not indicate where the connection was actually
dropped. To accomplish this, another utility known as tracert must be
used.
 The Tracert utility provides connectivity information about the path a
packet takes to reach the destination and about every router (hop) along
the way. It also indicates how long a packet takes to get from the source
to each hop and back (round trip time).
 Tracert can help identify where a packet may have been lost or delayed
due to bottlenecks or slowdowns in the network.
 The basic tracert utility will only allow up to 30 hops between a source
and destination device before it assumes that the destination is
unreachable. This number is adjustable by using the -h parameter. Other
modifiers, displayed as Options in the graphic, are also available.

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

31
 3/8/2016

 The traceroute command is also used for testing network

connections, but it gives a lot more information than ping.
Whenever you send a packet to a computer that is not on your
own local network, it has to go through one or more routers.
The purpose of the traceroute command is to try to list all the
routers on a path from your computer to some destination
computer.
 If you try other destinations, you might encounter cases where
three stars (* * *) are listed instead of a router. This might
indicate a buggy router (apparently, there are many of them out
there), or it might indicate that a router is configured so that it
refuses to cooperate with traceroute. If this happens a few times
in a row, you might as well give up by pressing CONTROL-C.

Prepared by : Zuraiti Bt Che Amat

How does tracert work?

 The information needed by traceroute is not automatically available, so
traceroute has to play some tricks to get the information. It actually uses ping in
a clever way: It is possible to specify that a ping packet will only be sent through
a given number of routers. The number is called the TTL (time-to-live) of the
packet. Every time a router forwards a packet, it decreases the packet's TTL by
1. If a router receives a packet with a TTL of 0, it considers that to be an error
and it sends an error message back to the packet's source. The traceroute
program uses this error message to determine the identity of the router. When
you run traceroute, it first sends out 3 ping packets with a TTL of 1. These
packets will produce a time-out error at the very first router on the path, so
traceroute now knows the identity of the first router. Next, it sends out 3
packets with a TTL of 2. These will generate an error at the second router along
the path, so traceroute learns the identity of the second router. Traceroute
continues in this way, with longer and longer TTL's, until the packets that it
sends actually reach the destination. Note that each line of output from
traceroute shows not just the identity of the router but also the round trip times
of each of the three ping packets. If traceroute fails to get an error response to a
given packet within three seconds, it prints a star (*) on the output line.
 It's possible for two packets that are sent to the same destination to follow
different paths through the Internet. In practice, however, it is unusual for the
path to change within the time period that traceroute runs. Prepared by : Zuraiti Bt Che Amat

32
 3/8/2016

7.1.8 Perform troubleshooting using Netstat

 Sometimes it is necessary to know which active TCP connections are
open and running on a networked host.
 Netstat is an important network utility that can be used to verify those
connections. Netstat lists the protocol in use, the local address and port
number, the foreign address and port number, and the state of the
connection.
 Unexplained TCP connections can pose a major security threat. This is
because they can indicate that something or someone is connected to the
local host. Additionally, unnecessary TCP connections can consume
valuable system resources thus slowing down the host's performance.
Netstat should be used to examine the open connections on a host when
performance appears to be compromised.
 Many useful Options are available for the netstat command.

Prepared by : Zuraiti Bt Che Amat

 Netstat (network statistics) adalah program

berbasis teks yang berfungsi untuk memantau
rangkaian jaringan pada suatu komputer, baik itu
jaringan LAN mahupun jaringan internet.

Bila saya memerlukan netstat ?

 misalkan suatu ketika anda sedang melayari internet
kemudian tiba-tiba connection menjadi sangat lambat
dan anda mengesyaki ada program di komputer anda
yang jadi penyebabnya. Jika hal itu yang anda alami
maka anda perlu memanggil program netstat untuk
melakukan pemeriksaan.
Prepared by : Zuraiti Bt Che Amat

33
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

7.1.9 Perform troubleshooting using

Nslookup
 When accessing applications or services across the network,
individuals usually rely on the DNS name instead of the IP
address.
 When a request is sent to that name, the host must first contact
the DNS server to resolve the name to the corresponding IP.
The host then uses IP to package the information for delivery.
 The nslookup utility allows an end-user to look up information
about a particular DNS name in the DNS server.
 When the nslookup command is issued, the information
returned includes the IP address of the DNS server being used
as well as the IP address associated with the specified DNS
name.
 Nslookup is often used as a troubleshooting tool for
determining if the DNS server is performing name resolution
as expected.
Prepared by : Zuraiti Bt Che Amat

34
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Understand connectivity
problems

Prepared by : Zuraiti Bt Che Amat

35
 3/8/2016

Outcomes 3 :
At the end of this subtopic, student should be able to:

1. Define common faults in cabling that cause

disconnectivity in network.
2. Discover various connectivity problems related to
cabling issues.
3. Diagnose connectivity problem based on
detection of IP address.

Prepared by : Zuraiti Bt Che Amat

1.Connectivity issue
 Connectivity problems occur on wireless
networks, wired networks and networks that use
both.
 When troubleshooting a network with both
wired and wireless connections, it is often best to
troubleshoot using a divide-and -conquer
technique to isolate the problem to either the
wired or wireless network.

Prepared by : Zuraiti Bt Che Amat

36
 3/8/2016

 The easiest way to determine if the problem is

with the wired or the wireless network is to:
1. Ping from a wireless client to the default gateway -
this verifies if the wireless client is connecting as
expected.
2. Ping from a wired client to the default gateway - this
verifies if the wired client is connecting as expected.
3. Ping from the wireless client to a wired client - this
verifies if the integrated router is functioning as
expected.

Prepared by : Zuraiti Bt Che Amat

2.Wiring Problems
 Cables are prone to failure. The most common cable to fail is the drop
cable, which is the one that connects a workstation to the wall jack.
Drop cables receive the most abuse, whether from being kicked, yanked,
bent, or twisted.
 When you determine that a cable might be the culprit of a network-
related problem, your first test of this theory is to replace the cable with
a known good cable. If the replacement cable works, you’ve solved the
problem.
 If you replace a drop cable and a patch cable but still haven’t gained
connectivity for that workstation, rather than try to re-cable behind the
walls, you still need to determine whether the problem is the cable.
 In this case, move the affected workstation to a different location where
you know the cable is in good working condition. If the workstation
functions properly at the new location, you know that the cable behind
the walls is at fault and you can work on fixing it. If the workstation fails
to communicate with a known good cable, the workstation itself has a
different problem to troubleshoot.
Prepared by : Zuraiti Bt Che Amat

37
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

3.Interference with the Network

Example situation :
 I once worked on a token ring network that had recently been rewired from
shielded twisted pair (STP) to unshielded twisted pair (UTP). There were
several ports on the network that, after the rewiring, were wrapping at the
Multistation Access Unit (MAU). After several weeks of intermittent problems,
a buzzing fluorescent light clued me in, and a quick test with a media tester
confirmed the problem. The wiring contractors had laid the new wiring in the
ceiling by following the old wiring paths. While this led the new wires to their
correct destinations, it also placed a lot of unshielded wire near fluorescent
lights, so the wires suffered interference. Fixing the problem required new
cabling to be installed at the expense of the poor contractor.
 Fiber optic cables do not suffer interference. This is one of the benefits of using
fiber optics. You can place them in locations that have high magnetic fields
without fear of network failure.
 When wiring a new office or planning a wiring layout with copper cabling, you
should avoid placement of the following near your cables:
 Power outlets
 Uninterruptible power supplies (UPS)
 Fluorescent lighting
 Strong magnets Prepared by : Zuraiti Bt Che Amat

38
 3/8/2016

4.Bad Wiring and Connectors

 Network performance is affected by several factors that
involve cabling: the connecting hardware, the patch and
drop cables, the cable’s characteristics, the number of
connecting hosts, and the care with which the cable has
been installed.You can end up with bad cabling from
simply not taking notice of what’s on the network.
 A properly installed cable is flexible and can be moved or
curved with no effect on network performance. However,
if you replace a Cat5 patch cable with a Cat3 cable, the
network performance will degrade. If you replace a patch
cable with a Cat3 cable that is longer than the cable it
replaced, network performance will further degrade.

Prepared by : Zuraiti Bt Che Amat

Bad Wiring and Connectors (cont)

 Sheathing on the cable is important to retain the twists in the wire,
which ensure that there is no crosstalk. If you remove the cable
sheathing, the network’s performance degrades. This happens if even
only one inch of cabling is in question. If the wires untwist and the cable
sheathing is removed, the network performance degrades much faster.
(Some tests have shown 5 to 10 times the rate of degradation, depending
on the length of the cable.)
 Kinked cables can cause network performance degradation as well. A
UTP cable can be wound up in a roll up to six inches in diameter with
no effect on the network. However, if that cable is wound more tightly
around a three-inch diameter, the performance breaks down. Any time a
cable is wound more tightly or kinked, connectivity loss will occur.
 Connectors are the source of termination problems. When a jack is
loose or sheathing is exposed for too long a length, the network will
show degraded performance or no performance at all. Incorrect
termination—in which the wires are not in the correct sequence—will
result in no connectivity.
Prepared by : Zuraiti Bt Che Amat

39
 3/8/2016

How to avoid bad wiring?

 Perform a few tasks at the time that you cable the
network:
1. Mark each cable end before cabling.
2. Pull the cables throughout the building, making certain that
there are no kinks, twists, or exposed wires, and that the
cable is away from any electrical or magnetic fixtures.
3. Punch down the cables at each wall jack and at the
corresponding patch panel.

Prepared by : Zuraiti Bt Che Amat

How to avoid bad wiring? (cont)

4. Test the cable between the wall jack and patch panel to ensure
it can carry a signal. Check for the following:
 Wire map: validate whether the cable termination has been done with the
correct pairings in the correct sequence.
 Signal attenuation: ensure that the signal loss is within acceptable limits
for the cabling specification.
 Length: verify whether the physical length is below the maximum for the
cabling specification, such as 100 meters for Ethernet over Cat5 cable.
 Propagation delays: check for the time that it takes for signals to travel
from one end of the cable to the other.
5. Install the networking equipment and workstations.

Prepared by : Zuraiti Bt Che Amat

40
 3/8/2016

5.Diagnose connectivity problem based on

detection of IP address.
Determining if your computer is obtaining the correct IP address
 If the physical connection to the wired or wireless host appears to be connecting as
expected, then check the IP configuration of the client.
 The IP configuration can have a major impact on the ability for a host to connect to the
network. An integrated router, such as the Linksys wireless router, acts as a DHCP
server for local wired and wireless clients and provides IP configuration, including the IP
address, subnet mask, default gateway, and possibly even IP addresses of DNS servers.
The DHCP server binds the IP address to a client's MAC address and stores that
information in a client table. On the home Linksys wireless router, this table can be
examined through the Status | Local Network page in the GUI.
 The client table information should match the local host information, which can be
obtained from the ipconfig /all command. Additionally, the IP address on the client must
be on the same network as the LAN interface of the Linksys device. The LAN interface of
the Linksys device should be set as the default gateway. If the client configuration
information does not agree with information in the client table, the address should be
released (ipconfig /release) and renewed (ipconfig /renew) to form a new binding.
 If both the wired and wireless clients are obtaining the correct IP configuration, and can
connect to the Linksys device, but are unable to ping each other, the problem is most
likely occurring on the Linksys device. Check all configurations on the Linksys device to
ensure no security restrictions could be causing the issue.

Prepared by : Zuraiti Bt Che Amat

Wired and wireless hosts can connect to each other, but not to the Internet
 If hosts on the wired and wireless local network can connect to the integrated router and
with other hosts on the local network, but not to the Internet, the problem may be in the
connection between the integrated router and the ISP.
 There are many ways to verify connectivity between the integrated router and the ISP.
Using the GUI, one way to check connectivity is to examine the router status page. It
should show the IP address assigned by the ISP and should indicate if the connection is
established.
 If this page shows no connection, the integrated router may not be connected. Check all
physical connections and LED indicators. If the DSL or Cable modem is a separate
device, check those connections and indicators as well. If the ISP requires a login name
or password, check that they are configured to match those given by the ISP. Using the
GUI, password configurations can normally be located on the Setup configuration page.
Next, try to re-establish connectivity by clicking the Connect, or IP address renew,
button on the status page. If the integrated router will still not connect, contact the ISP
to see if the issue is occurring from their end.
 If the status page shows that the connection is up, but a ping to an Internet site fails, it
may be that the individual site is down. Try pinging another site to see if that is
successful. If not, check for security measures that are enabled that may be creating the
issue, such as port filtering.

Prepared by : Zuraiti Bt Che Amat

41
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Understand troubleshooting
and the Helpdesk

Prepared by : Zuraiti Bt Che Amat

42
 3/8/2016

Outcomes 4 :
At the end of this subtopic, student should be able to:

1. Record troubleshooting Document.

2. Define the purpose of outside sources in
troubleshooting.
3. Define the purpose of Helpdesk in troubleshooting.

Prepared by : Zuraiti Bt Che Amat

Record troubleshooting Document

Prepared by : Zuraiti Bt Che Amat

43
 3/8/2016

7.3.1 Record troubleshooting Document.

 Network documentation is an important part of any
troubleshooting process. Network documentation should
include a normal or baseline measurement of network
performance against which potential problems can be judged.
 The performance baseline can include the types of traffic
normally expected, as well as the volume of traffic to and from
servers and network devices. The baseline should be
documented just after the network is installed, when it is
running optimally. Baseline performance should be re-
established after any major changes to the network are
implemented.
 Additionally, documentation such as topology maps, network
diagrams and addressing schemes can provide valuable
information when a troubleshooter is trying to understand the
physical layout of the network and the logical flow of
information.
Prepared by : Zuraiti Bt Che Amat

7.3.1 Record troubleshooting Document.

(cont)
 When troubleshooting, documentation should be
maintained during the troubleshooting process. This
documentation can be a valuable reference and can be
used when future issues arise.
 Good troubleshooting documentation should include:
Initial problem
Steps taken to isolate the problem
Results of all steps taken, both successful and
unsuccessful
Final determined cause of the problem
Final problem resolution
Preventative measures

Prepared by : Zuraiti Bt Che Amat

44
 3/8/2016

Define the purpose of outside

sources in troubleshooting.

Prepared by : Zuraiti Bt Che Amat

7.3.2 Define the purpose of outside sources

in troubleshooting.
 If, during the troubleshooting process, the
troubleshooter is unable to determine the
problem and its resolution, it might be necessary
to obtain assistance from outside sources.
 Some of the most common sources for help
include:
 Previously kept documentation
 Online FAQs (Frequently Asked Questions)
 Colleagues and other network professionals
 Internet forums

Prepared by : Zuraiti Bt Che Amat

45
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

46
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

47
 3/8/2016

Define the purpose of Helpdesk in

troubleshooting.

Prepared by : Zuraiti Bt Che Amat

7.3.3 Define the purpose of Helpdesk in

troubleshooting.
 The helpdesk is a group of individuals with the
knowledge and tools required to help diagnose and
correct common problems.
 It provides assistance for the end-user to determine if
a problem exists, the nature of the problem, and the
solution.
 If necessary, the helpdesk can take control of a local
host through remote access software. This allows
helpdesk technicians to run diagnostic programs and
interact with the host and network without having to
physically travel to a job site.

Prepared by : Zuraiti Bt Che Amat

48
 3/8/2016

 The helpdesk will require information on any service or

support plans that are in place along with specific details of the
affected equipment.
 The helpdesk will require information specific to the problem
including:
 Symptoms encountered
 Who encountered the problem
 When the problem manifests
 Steps taken to identify the problem
 Results of steps taken
 If this is a follow-up call, be prepared to provide the date and
time of the previous call, the ticket number, and name of the
technician.

Prepared by : Zuraiti Bt Che Amat

 A helpdesk is generally organized in a series of levels of

experience and knowledge.
 If the first-level helpdesk staff is unable to solve the problem
they may escalate the problem to a higher level. Higher level
staff are generally more knowledgeable and have access to
resources and tools that the first-level helpdesk does not.
 Record all information regarding the interaction with the
helpdesk, such as:
 Time/date of call
 Name/ID of technician
 Problem reported
 Course of action taken
 Resolution/escalation
 Next steps (follow-up)

Prepared by : Zuraiti Bt Che Amat

49
 3/8/2016

KEY POINTS

Prepared by : Zuraiti Bt Che Amat

Key Points
 TCP/IP utilities are excellent tools for use in troubleshooting network problems.
 Tracert provides information about the path that data takes between two hosts on an IP
internetwork.
 Both Tracert and ping use the ICMP protocol.
 Ping will tell you whether another host is reachable.
 ARP uses the Address Resolution Protocol for resolving IP addresses to physical
addresses.
 Netstat shows IP network status information.
 Nbtstat shows NetBIOS over TCP/IP status.
 Nslookup is used to query the DNS database.
 On a Windows machine, you can use either Winipcfg or Ipconfig, depending on the
Windows version, to show TCP/IP configuration information for the network adapters.
 On a UNIX machine, Ifconfig is used to configure IP information at the startup and can

also be used afterward to change adapter configuration .

Prepared by : Zuraiti Bt Che Amat

50
 3/8/2016

Key Points (cont)

 Use the same troubleshooting method whether the problem you’ve encountered has to
do with physical or logical problems.
 Troubleshooting includes the following steps:
 Establish the symptoms.
 Identify the area affected by the problem.
 Determine what has changed & Select a probable cause for the problem.
 Implement a solution.
 Test the result. Recognize whether the solution is successful, and if it was
unsuccessful, select the next most probable cause and solution.
 Document the solution.
 When a computer does not obtain an IP address, the problem is related to DHCP.
 When a computer does not recognize the names of URLs on the Internet, it is usually a
DNS problem.
 WINS problems are sometimes caused by static entries for hosts with more than one
NIC.

Prepared by : Zuraiti Bt Che Amat

Key Points (cont)

 Tools are used to troubleshoot networks, especially when cabling problems occur.
 A wire crimper is used to add a male jack at the end of the cable.
 A punch down tool is used to add a female jack (a wall jack or patch panel jack).
 There are several types of media testers. A digital voltmeter tests signal power. A time
domain reflectometer tests for cable problems.
 Optical testers are used strictly for fiber optic cabling.
 A tone generator is useful in finding crosstalk and identifying unmarked cables.
 Visual indicators will display whether a link has been successfully made and whether
there are too many collisions.
 The troubleshooting method consists of these steps:
 Establish the symptoms.
 Discover what has been affected.
 Determine what has changed.
 Decide on a probable cause.
 Implement a solution.
 Test the results.
 Determine whether you’ve been successful.

Prepared by : Zuraiti Bt Che Amat

51
 3/8/2016

QUIZZES

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

52
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

53
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

54
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

55
 3/8/2016

Prepared by : Zuraiti Bt Che Amat

Prepared by : Zuraiti Bt Che Amat

56