Troubleshooting Hardware and Cabling

The most important thing to remember in troubleshooting is to tackle your problems logically so you don’t miss any important components or steps. You must confirm the health of all the components that make up the firewall. When addressing PIX firewall problems, you would be best served using the OSI model to guide your efforts. This model was created to guide development efforts in networking by dividing functions and services into individual layers. Per the OSI model, peer layers communicate with each other. For example, the network layer at one host communicates with the network layer at another host.

The approach advocated in this chapter is based on the OSI model shown in Figure 12.1. Problems are tackled starting at the lowest layer, such as validating hardware and cabling at the physical layer. Only when the components at the lower layer have been validated do you turn your attention to components at a higher layer.