telnet session. No command should be selected that will cause the debug output to create additional traffic that creates debug output. If this occurs, the telnet session will rapidly saturate the link with traffic or the router will exhaust one or more resources. A good rule to follow to prevent this recursion of traffic is “Never debug any activity on the port where the session is established”. The output of the different debug commands varies. Some may frequently generate many lines while others produce a line or two of output every few minutes. Another IOS software service that will enhance the usefulness of the debug output is the timestamps command. This command will put a timestamp on a debug message. This information provides the time when the debug event occurred and the duration of time between events. The following command configures a timestamp that will show the hour:minute:second of the output, the amount of time since the router was last powered up, and when a reload command was executed: GAD(config)#service timestamps debug uptime The no debug all command or the undebug all command turn off all diagnostic output. To disable a particular debug command, use the “no” form of the command. For example, if debug for monitoring RIP was enabled with the command debug ip rip, it can be disabled with no debug ip rip. To view what is currently being examined by a debug command, use show debugging. Lab Activity Lab Exercise: Troubleshooting Routing Issues with Debug This lab is to utilize a systematic OSI troubleshooting process to diagnose routing problems.
Content Summary An understanding of the following key points should have been achieved: