IOS Configuration Modes

IOS Configuration Modes

Global Configuration Mode

The primary configuration mode is called global configuration or global config. From global config, CLI configuration changes are made that affect the operation of the device as a whole.

We also use the global config mode as a precursor to accessing specific configuration modes.

The following CLI command is used to take the device from privileged EXEC mode to the global configuration mode and to allow entry of configuration commands from a terminal:

Router#configure terminal

Once the command is executed, the prompt changes to show that the router is in global configuration mode.


Specific Configuration Modes

From the global config mode, there are many different configuration modes that may be entered. Each of these modes allows the configuration of a particular part or function of the IOS device. The list below shows a few of them:
Interface mode - to configure one of the network interfaces (Fa0/0, S0/0/0,..)
Line mode - to configure one of the lines (physical or virtual) (console, AUX, VTY,..)
Router mode - to configure the parameters for one of the routing protocols

The figure shows the prompts for some modes. Remember, as configuration changes are made within an interface or process, the changes only affect that interface or process.

To exit a specific configuration mode and return to global configuration mode, enter exit at a prompt. To leave configuration mode completely and return to privileged EXEC mode, enter end or use the key sequence Ctrl-Z.

Once a change has been made from the global mode, it is good practice to save it to the startup configuration file stored in NVRAM. This prevents changes from being lost due to power failure or a deliberate restart. The command to save the running configuration to startup configuration file is:

Router#copy running-config startup-config

IOS Configuration Modes
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