Cisco IOS Software Survival Skills

This chapter describes what you need to know about the Cisco IOS software (the software that runs the access server) before you configure the access server using the command-line interface (CLI). This chapter includes:

Understanding these concepts will save you time and aggravation later. 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 the next chapter, "Basic Configuration."

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

There are many different command modes that you will need to use to configure the access server. Each command mode restricts you to a subset of commands. If you are having trouble 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.

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

Router> enable
Router# configure terminal
Router(config)# interface ethernet 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.

Note You can press Ctrl-Z in any mode to return to enable mode (Router#), instead of entering exit.

Undoing a Command or Feature

If you want to undo a command you entered or disable a feature, 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 they will not be 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

Now that you have learned some Cisco IOS software basics, you can begin to configure the access server using the CLI.

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 are having 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.
If you want 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 they will not be lost if there is a system reload or power outage.

Proceed to the next chapter, "Basic Configuration," to begin configuring the access server.

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