2.2.3: With the OSI reference model as a guide, you can define, isolate, and solve most network-related issues. As mentioned previously, you can approach an issue starting with the layer most likely to be the problem. If you are unfamiliar with the issue and its symptoms, the following bottom-up approach identifies key points to consider in each layer:
• Physical layer (1): Check power, connectivity, cables, LEDs, and environmental issues such as temperature and humidity.
• Data link layer (2): Check switch and NIC configurations and operation. Substituting a NIC or switch at this layer often can isolate the issue.
• Network layer (3): Check IP configurations on devices, and use commands such as ping, ipconfig, and ...