CISCO IOS in a Nutshell

Loading Configuration Files

Loading and saving configuration files is much simpler than loading a kernel image. This section summarizes the commands that load and save the configuration.

Loading the running-config

Once loaded, the running configuration will immediately be used by the router. Use these commands to load it using either TFTP or RCP:

Router#copy tftp running-config        
               (for TFTP)
Router#copy rcp running-config         
               (for RCP)

Loading the startup-config

The startup configuration is not used until the router is rebooted. Loading the startup configuration can be dangerous, because the router doesn’t parse the configuration file and won’t give you any warning if the file has errors. The configuration is not parsed until the router is rebooted—and if the configuration is incorrect, the router may not boot properly. Therefore, use the following commands with care:

Router#copy tftp startup-config         
               (for TFTP)
Router#copy rcp startup-config          
               (for RCP)

Saving running-config to startup-config

The following command is the most important of all. If you don’t save your running configuration, all your configuration changes will be lost during the next reboot of the device. Once you are satisfied that your current router configuration is correct, copy your configuration to the startup configuration with this command:

Router#copy running-config startup-config

Viewing a Configuration

The following commands display the startup or the running configuration:

Router#show startup-config
Router#show running-config ...