Table Of Contents

Cisco IOS Software Basics

Getting Help

Understanding Command Modes

Undoing a Command or Feature

Saving Configuration Changes

Where to Go Next

Cisco IOS Software Basics

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This chapter describes what you need to know about the Cisco IOS software before you configure the Cisco IAD using the command-line interface (CLI). The following sections are included:

•Getting Help

•Understanding Command Modes

•Undoing a Command or Feature

•Saving Configuration Changes

•Where to Go Next

Understanding these concepts will save time as you begin to use the CLI. If you have never used the Cisco IOS software or need a refresher, take a few minutes to read this chapter before you proceed to the next chapter.

If you are already familiar with the Cisco IOS software, proceed to "Configuration Using the Command-Line Interface."

Getting Help

Use the question mark (?) and arrow keys to help you enter commands:

•For a list of available commands, enter a question mark:

Router> ?

•To complete a command, enter a few known characters followed by a question mark (with no space):

Router> s?

•For a list of command variables, enter the command followed by a space and a question mark:

Router> show ?

•To redisplay a command you previously entered, press the up arrow key. You can continue to press the up arrow key for more commands.

Understanding Command Modes

The Cisco IOS user interface is divided into different modes. Each command mode permits you to configure different components on your Cisco IAD. The commands available at any given time depend on which mode you are currently in. Entering a question mark (?) at the prompt displays a list of commands available for each command mode. Table 3-1 lists the most common command modes.

Table 3-1 Common Command Modes

Command Mode	Access Method	Router Prompt Displayed	Exit Method
User EXEC	Log in.	Router> Hostname>	Use the logout command.
Privileged EXEC (also called "enabled mode")	From user EXEC mode, enter the enable command.	Router# Hostname#	To exit to user EXEC mode, use the disable, exit, or logout command.
Global configuration	From the privileged EXEC mode, enter the configure terminal command.	Router(config)# Hostname(config)#	To exit to privileged EXEC mode, use the exit or end command, or press Ctrl-z.
Interface configuration	From the global configuration mode, enter the interface type number command, such as interface serial 0.	Router(config-if)# Hostname(config-if)#	To exit to global configuration mode, use the exit command. To exit directly to privileged EXEC mode, press Ctrl-z.

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Tip Each command mode restricts you to a subset of commands. If you are having trouble entering a command, check the prompt, and enter the question mark (?) for a list of available commands. You might be in the wrong command mode or using the wrong syntax.

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In the following example, notice how the prompt changes after each command to indicate a new command mode:

Router> enable

Password: enable password

Router# configure terminal

Router(config)# interface serial 0

Router(config-if)# line 0

Router(config-line)# controller t1 0

Router(config-controller)# exit

Router(config)# exit

Router#

%SYS-5-CONFIG_I: Configured from console by console

The last message is normal and does not indicate an error. Press Return to get the Router# prompt.

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Note You can press Ctrl-z in any mode to immediately return to the privileged EXEC, or enabled, mode (Router#), instead of entering exit, which returns you to the previous mode.

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Undoing a Command or Feature

If you want to disable a feature or undo a command that you have entered, enter the keyword no before most commands; for example, no ip routing.

Saving Configuration Changes

You need to enter the copy running-config startup-config command to save your configuration changes to nonvolatile random-access memory (NVRAM), so that the changes are not lost if there is a system reload or power outage. For example:

Router# copy running-config startup-config

Building configuration...

It might take a minute or two to save the configuration to NVRAM. After the configuration has been saved, the following appears:

[OK]

Router#

Where to Go Next

When you understand the Cisco IOS software basics, you can configure the Cisco IAD using the CLI.

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Tip Remember that:

•You can use the question mark (?) and arrow keys to help you enter commands.

•Each command mode restricts you to a set of commands. If you have difficulty entering a command, check the prompt and then enter the question mark (?) for a list of available commands. You might be in the wrong command mode or using the wrong syntax.

•To disable a feature, enter the keyword no before the command; for example, no ip routing.

•You need to save your configuration changes to NVRAM so that the changes are not lost if there is a system reload or power outage.

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Proceed to "Configuration Using the Command-Line Interface," to begin configuring the Cisco IAD.