This chapter introduced troubleshooting fundamentals. You first examined potential software issues. The software provides details about possible caveats, security vulnerabilities, and other known issues that can help expedite the troubleshooting process.

The second issue addressed was hardware problems. Catalyst switch commands such as show module and show test were cited to pinpoint hardware failure. Other commands were also cited to address specific Catalyst switching issues. Troubleshooting guidelines were provided to deal with issues such as Supervisor or an MSFC missing from the chassis.

The discussion turned to port errors seen on the network. Some of the more common fields within the show port command were discussed.

The importance of syslog and trace feature were examined. Both syslog and trace commands, in most cases, provide meaningful information about the errors seen by the switch. After you understand the root cause of the problem, you can take steps to resolve the issue.

If command-line syntax, syslog, and trace cannot provide further detail about the nature of the network problem, the SPAN and RSPAN features can be used to examine the actual packets on the network.

Finally, this chapter cited the importance behind field alerts and PSIRTs.