The Bottom-Up Troubleshooting Approach
The bottom-up troubleshooting approach also uses the OSI model as its guiding principle with the physical layer (bottom layer of the OSI seven-layer network model) as the starting point. In this approach, you work your way layer by layer up toward the application layer and verify that relevant network elements are operating correctly.
Checking the link light first to see if the physical layer is operational so it's bottom-to-top.