Module 5 : Summary

Summary

This page summarizes the topics discussed in this module. The default configuration register setting can be changed with the global configuration mode command config-register. The boot sequence for the Cisco IOS can specify the fallback sequence that is used to boot Cisco IOS software. A common fallback sequence would be to load first from flash memory, which is not vulnerable to network failures. The network server would be used next if the flash memory were corrupt. Finally if the first two methods failed the router would boot from ROM. However, the system image in ROM will likely be a subset of the full Cisco IOS image. The command copy running-config startup-config saves the configuration commands in NVRAM. The router will execute the boot system commands as needed in the order in which they were originally entered in the configuration mode. If a configuration register setting is incorrect, the Cisco IOS will not load from flash. To troubleshoot the boot sequence, use the show running-config command and look for a boot system statement near the top of the configuration. If the boot system statement points to an incorrect IOS image, use the no form of the command to delete the statement. The two types of software required to operate a router and a switch are the operating systems and the configuration. The Cisco IOS allows the hardware to function. The configuration file or config is the software that contains the instructions that define how the device is to route or switch the packets that enter the device. The naming convention for Cisco IOS files includes four parts. The first part of the Cisco IOS file name identifies the hardware platform for which this image is designed. The second part of the Cisco IOS file name identifies the various features that this file contains. The third part of the file name indicates the file format. It specifies if the Cisco IOS is stored in flash in a compressed format and whether it is relocatable. The fourth part of the file name identifies the release of the Cisco IOS. As newer versions of the Cisco IOS are developed, the numerical version number increases. The active configuration for a Cisco router is maintained in RAM and the default location for the startup configuration is NVRAM. The copy running-config tftp command can be used to back up copies of the configuration to a TFTP server. Another way to create a backup copy of the configuration is to capture the output of the show running-config command. To do this from the terminal session, copy the output, paste it to a text file, and then save the text file. After the capture is complete, the configuration file needs to be edited to remove extra text. To add a comment, begin a line with an exclamation mark (!).