- Command Line Modes

Command Line Modes

Access to a router or switch command line is referred to as an EXEC session. There are two levels of access: user EXEC and privileged EXEC. In user exec mode, you have limited access to information and diagnostic commands, and you are not able to make configuration changes to the router. Privileged EXEC mode gives you the complete command set and full authority to change or erase the configuration.

When you connect to a router using the console port, you see a message like this:

Router Con0 is now available.
Press RETURN to get started!

Pressing Return takes you to the User Exec Prompt, which looks like this:

Router>

To go to Privileged EXEC mode, you must enter the command enable. The prompt will change from > to #, as shown:

Router>enable Router#

From this point, you can enter commands to view the status and settings of the router, make some kinds of changes, and erase, back up, or restore the IOS and configuration files.
To make most kinds of changes, however, you must enter the Global Configuration mode. This is done by entering the command configure terminal from the Privileged EXEC mode:

Router#configure terminal
Router(config)#


Notice that the command prompt changes to Router(config)#. From this prompt, you can make changes to functions that affect the whole router, or you can enter a more specific configuration mode to work with specialized functions. Some of the possible modes are listed and explained in the following:

Router(config)#interface serial 0
Router(config-if)#


This is the Interface configuration mode. Here you can set IP addresses and subnet masks, change speed, duplex, clock rate and bandwidth, or change the Layer 2 encapsulation of the interface. Changes made here affect only the interface you specified in the interface command.

Router(config)#line console 0
Router(config-line)#


Line Configuration mode allows you to set up line parameters. Lines include the console, AUX, TTY, and VTY connections. The console and aux lines are the local administration connections. TTY lines are synchronous serial connections, usually for analog dialup access with modems. The VTY lines are virtual connections for Telnet access to the router to perform remote administration over an IP network.

Router(config)#router rip
Router(config-router)#