4. Troubleshooting Network
• Network troubleshooting is the collective measures and
processes used to identify, diagnose and resolve
problems and issues within a computer network.
• It is a systematic process that aims to resolve problems
and restore normal network operations within the
network.
• Network troubleshooting is primarily done by network
engineers or administrators to repair or optimize a
network. It is generally done to recover and establish
network or Internet connections on end nodes/devices.
• Link: https://youtu.be/0-eefKkafhs
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5. Troubleshooting Network
Some of the processes within network troubleshooting
include but are not limited to:
• Finding and resolving problems and establishing
Internet/network connection of a computer/device/node
• Configuring a router, switch or any network management
device
• Installing cables or Wi-Fi devices
• Updating firmware devices on router switch
• Removing viruses
• Adding, configuring and reinstalling a network printer
Network troubleshooting can be a manual or automated
task. When using automated tools, network
management can be done using network diagnostic
software.
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7. Network Utilities
• Network Utilities – provides a variety tools that can
be used related to computer network information
gathering and analysis.
• Network Utility shows information about each of
your network connections, including the Mac
Address of the interface, the IP addresses assigned
to it, its speed and status, a count of
data packets sent and received, and a count of
transmission errors and collisions.
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8. Contd…
Network Utilities
Examples of what the Network Utility can help with:
• Check your network connection
• View network routing tables and statistics
• Test whether you can contact another computer
• Test your DNS server
• Trace the paths of your network traffic
• Check for open TCP ports
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9. Ipconfig
• Ipconfig (sometimes written as IPCONFIG) is a
command line tool used to control the network
connections on Windows NT/2000/XP machines.
• Ipconfig displays all current TCP/IP network
configuration values and refreshes Dynamic Host
Configuration Protocol (DHCP) and Domain Name
System (DNS) settings.
• Displays current info of your network
• IP address of system
• Ip add of router
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10. Ipconfig
The syntax for using ipconfig is:
>ipconfig /parameter_name.
For example, "ipconfig /all" displays the entire TCP/IP
configuration of all available network adapters.
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13. ping
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• Ping is a basic Internet program that allows a user to verify
that a particular IP address exists and can accept requests.
• Ping is used diagnostically to ensure that a host computer
the user is trying to reach is actually operating. Ping works
by sending an Internet Control Message Protocol (ICMP)
Echo Request to a specified interface on the network and
waiting for a reply. Ping can be used for troubleshooting to
test connectivity and determine response time.
• Allow you to send a signal to another device, if a device is
active it will send you reply back.
• It’s a subset of ICMP.
• Echo request
• Echo response
14. ping
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• As a verb, ping means "to get the attention of" or "to
check for the presence of" another party online. The
computer acronym (for Packet Internet or Inter-
Network Groper) was contrived to match the
submariners' term for the sound of a returned sonar
pulse.
• Tip: To find out the dot address (such as
205.245.172.72) for a given domain name, Windows
users can go to their command prompt screen
(start/run/cmd) and enter ping xxxxx.yyy (where xxxxx
is the second-level domain name like "whatis" and yyy
is the top-level domain name like "com").
19. Tracert/ Traceroute
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• Trace the route to HOST
• Tracert is a Windows based command-line tool that you can
use to trace the path that an Internet Protocol (IP) packet
takes to its destination from a source.
• Tracert will determine the path taken to a destination. It
does this by sending Internet Control Message Protocol
(ICMP) Echo Request messages to the destination.
• When sending traffic to the destination, it will incrementally
increase the Time to Live (TTL) field values to aid in finding
the path taken to that destination address. The path is
outlined from this process.
• Ref:
https://www.mediacollege.com/internet/troubleshooter/tra
ceroute.html
22. nslookup
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• Query the nameserver for the IP address of the
given HOST optionally using a specified DNS
server.
• nslookup is the name of a program that lets an
Internet server administrator or any computer user
enter a host name (for example, "whatis.com") and
find out the corresponding IP address. It will also
do reverse name lookup and find the host name for
an IP address you specify.
23. nslookup
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• For example, if you entered “www.whatis.com" (which is one of the
TechTarget sites), you would receive as a response our IP address, which
happens to be : 192.168.34.1
• Or if you entered "192.168.34.1", it would return "sites.techtarget.com".
• nslookup sends a domain name query packet to a designated (or
defaulted) domain name system (DNS) server. Depending on the system
you are using, the default may be the local DNS name server at your
service provider, some intermediate name server, or the root server
system for the entire domain name system hierarchy.
• Using the Linux and possibly other versions of nslookup, you can locate
other information associated with the host name or IP address, such as
associated mail services. nslookup is included with some UNIX-based
operating systems and in later Windows systems. In Windows XP, the
command can be entered on the "Command prompt" screen. A more
limited alternative to nslookup for looking up an IP address is
the ping command.
25. arp
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• Address Resolution Protocol (ARP) is a protocol for mapping
an Internet Protocol address (IP address) to a physical
machine address that is recognized in the local network.
• For example, in IP Version 4, the most common level of IP in
use today, an address is 32 bits long.
• In an Ethernet local area network, however, addresses for
attached devices are 48 bits long. (The physical machine
address is also known as a Media Access Control or MAC
address.)
• A table, usually called the ARP cache, is used to maintain a
correlation between each MAC address and its
corresponding IP address. ARP provides the protocol rules
for making this correlation and providing address conversion
in both directions.
27. netstat
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• Print network connections, routing tables, interface
statistics, masquerade connections, and multicast
memberships.
• Netstat is a common command
line TCP/IP networking utility available in most versions
of Windows, Linux, UNIX and other operating systems.
Netstat provides information and statistics
about protocols in use and current TCP/IP network
connections. (The name derives from the
words network and statistics.)
• Ref:
https://searchnetworking.techtarget.com/definition/ne
tstat
29. nbtstat
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• Displays NetBIOS over TCP/IP (NetBT) protocol
statistics, NetBIOS name tables for both the local
computer and remote computers, and the NetBIOS
name cache.
• nbtstat allows a refresh of the NetBIOS name cache
and the names registered with Windows Internet
Name Service (WINS). Used without
parameters, nbtstat displays help.
• Ref: https://docs.microsoft.com/en-us/windows-
server/administration/windows-commands/nbtstat
