Using the OSI Model to Troubleshoot Networks

Question 1

Understanding the Bottom Up Troubleshooting Technique

Answer 1

• Starting Point: Begin at the Physical layer of the OSI reference model.
• Layer-by-Layer Approach: Progressively work through each layer toward the Application layer.
• Isolation: Continuously narrow down possible causes until the problem is isolated.
• Example: If a workstation can’t connect to the network, check physical connections first, then move up the layers (Data Link, Network, etc.) to identify the issue12.

Question 2

Understanding the Top Down Troubleshooting Technique

Answer 2

• Starts at the Application Layer: Begin troubleshooting from the top layer of the OSI model (Application layer).
• Works Toward the Physical Layer: Progressively move down the OSI model layers (toward the Physical layer).
• Application Focus: Useful when you suspect an issue within an application rather than the network or internetwork devices12.
• Example: An administrator might examine or restart network applications on a workstation that lost connectivity to the network.

Question 3

Troubleshooting Physical Layer Connectivity