cisco 200 301 practice test

cisco 200 301 practice test.16.5.5 Debugging OverviewOne disadvantage of using the show commands is that they only display what is currently stored in memory and this content is static. To get the most up-to-date information, you must keep executing the command. Also, the show command does not always display detailed troubleshooting information. For example, you may want the router to tell you when a particular event occurred and to display the contents of some packets associated with that event. The show command cannot do this, but the debug command can. The debug command is one of the most powerful IOS troubleshooting tools, allowing you to view events and problems in real time on your Cisco device.However, the debug command has a downside: with this feature enabled, the router must check and display many things, which will affect IOS performance. For example, if you want to view every IP packet that flows through the router, the router must examine each packet to determine if it is an IP packet before displaying part or all of the packet on the screen. On a busy router, this debugging process can cause a dramatic performance degradation. Therefore, the debugging process should be enabled on the router with caution; perhaps wait until off-hours or when it is not busy before using this tool.Practical LessonsNever use the command debug all - this will enable debugging for every IOS feature enabled on the router. If you do this on a busy IOS device, you will see pages and pages of various output messages that could cause the device to crash.Chapter 16 Managing IOS Devices 413Often, the debug command is used to perform complex troubleshooting. For example, if you have used various show commands to try to find the cause of a problem and have failed, you should turn to the debug command to find the root cause of the problem. This command contains a large number of options and parameters, and to understand them, use the context-sensitive help. Many of the later chapters in this book will describe specific debug commands and their usage. Debugging can be enabled only in privileged EXEC mode. If you are not connected to the device through the console port, you must also execute the privileged EXEC command terminal monitor after debugging is enabled, in order to see the debug output.Video 16.13A multimedia demonstration of using debugging on a router is included in the digital resources that accompany this book.It is important to disable the debugging process once the problem is resolved or you no longer need to see debugging. To do this, prefix the debug command with the parameter no, or you can execute one of the following two commands.