Troubleshooting Network Layers: A Comprehensive Report

This report provides a detailed overview of troubleshooting techniques for various network layers, including the physical, internet, transport, and application layers. It begins with the physical layer, emphasizing the importance of network monitoring tools and techniques like pinging and link testing to identify issues related to cabling and connection lights. The report then explores the internet layer, focusing on addressing, routing, and packaging problems, and how to resolve them using tools like WireShark and route/Tracert commands. The transport layer is addressed next, with an emphasis on resolving issues related to blocked ports, firewalls, and QoS configurations. Finally, the application layer is discussed, highlighting common problems like addressing conflicts, collisions, and CRC errors, with a focus on using network monitoring tools to evaluate logs and identify broadcast storms and other issues. The report references several sources to support its information.

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Troubleshooting the Physical Network layer
This is the physical layer of the DARPA network architecture and was designed to be
independent of method used to access the network. When there is no data transfer, this layer is
always likely the problem and can be troubleshot using network monitoring tools and techniques
such as pinging to see if there is communication with another target. Further, network monitoring
tools will show if there is data and communication within the network. Just by viewing connection
details on the networking console of a computer, one will see if data is being transported or not and
then initiate remedial measures. The Ping tool is excellent for troubleshooting problems within this
layer because the common problems are due to routing and addressing. Pinging the loop-back
address will provide information if the IP is properly configured and is working (Mudracola, 2016).
Investigating blunders at this level incorporate utilizing link testing devices to guarantee cabling is
working appropriately. Connection lights on arrange gadgets are additionally an extraordinary
approach to investigate issues at Layer 1. On the off chance that the connection light is green, at that
point Layer 1 is working. In the event that the connection light is another shading or not
illuminating by any stretch of the imagination, at that point there is an issue at this layer. Simple
approaches to test this are swapping out links with a working link, swapping SFPs, or modules, and
utilizing link testing
Troubleshooting the Internet Layer
This layer plays the role of addressing, routing, and packaging. When there is a problem in
this layer, it is likely the cause is due to one of its three listed functions ( addressing, routing, and
packaging). It can be troubleshot to solve problems by first checking the IP addressing table and the
MAC addressing tables. By viewing the logs from the ICMP (Internet control message protocol),
one can see any error messages of undelivered packets and resolve this through addressing and
routing. Using a tool like WireShark or other network monitoring tools can help in troubleshooting
the layers’ problems. The route tool and the Tracert are some of the tools that can be used for
trouble shooting this layer (Davies, 2006)
Troubleshooting the Transport Layer
This layer is responsible for giving the application layer datagram and communication
services. Problems with this layer can be solved using packet and session tracer tools to monitor
activity. Most problems in this layer are mainly because of blocked ports and one area to look at is
the firewall and the firewall access lists that are blocking TCP/ UPD ports. The next area to check is

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QoS which when enabled, can block traffic or lead to slowing of traffic and result in large frames
being fragmented as well (Alpern & Shimonski, 2010).
Troubleshooting the Application Layer
This layer gives applications the capability to access services of other layers and problems
that are likely to be experienced in this layer include addressing (MAC addressing), collisions,
duplex errors, spanning tree issues, and CRC frame errors. Troubleshooting requires viewing logs
for broadcast storms, the runts and giants, and collision information that can be evaluated using
network monitoring tools (Tetz, n.d).

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References
Alpern, N. J., & Shimonski, R. (2010). Eleventh hour network+: Exam N10-004 study guide.
Rockland, Mass: Syngress.
Davies, J. (2006). Chapter 16 – Troubleshooting TCP/IP . Technet-Microsoft. Retrieved 27
November 2017, from https://technet.microsoft.com/en-us/library/bb727023.aspx
Mudrakola, S. (2016). Network Problems? Troubleshoot with the OSI Model. Techgenix.com.
Retrieved 27 November 2017, from http://techgenix.com/network-troubleshooting-osi/
Tetz, E. (n.d). CISCO Networking: Application Layer Troubleshooting. Retrieved 27 November
2017, from http://www.dummies.com/programming/networking/cisco/cisco-networking-
application-layer-troubleshooting/