You can configure your router from a PC that is connected through the console port by using terminal emulation software. The PC uses this software to send commands to your router. The table below lists some common types of terminal emulation software that you can use, depending on the operating system that you are running.

You can use the terminal emulation software to change settings for the router that is connected to the PC. Configure the software to the following standard VT-100 emulation settings so that your PC can communicate with your router:

• 9600 baud
• 8 data bits
• No parity
• 1 stop bit
• No flow control

These settings should match the default settings of your router. To change the router baud, data bits, parity, or stop bits settings, you must reconfigure parameters in the ROM monitor. For more information, see ROM Monitor . To change the router flow control setting, use the flowcontrol command in global configuration mode.

For information on how to enter global configuration mode so that you can configure your router, see the Entering Global Configuration Mode section later in this chapter.

This section describes the Cisco IOS command mode structure. Each command mode supports specific Cisco IOS commands. For example, you can use the interface type number command only from global configuration mode.

The following Cisco IOS command modes are hierarchical. When you begin a router session, you are in user EXEC mode.

• User EXEC
• Privileged EXEC
• Global configuration

The table below lists the command modes that are used in this guide, describes how to access each mode, shows the prompt for each mode, and explains how to exit to a mode or enter another mode. Because each mode configures different router elements, you might need to enter and exit modes frequently. You can see a list of available commands for a particular mode by entering a question mark (?) at the prompt. For a description of each command, including syntax, see the Cisco IOS Release 12.3 documentation set.

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

For a list of available commands for a prticular command mode, enter a question mark:

Router> ?
access-enable				Create a temporary access-list entry
access-profile				Apply user-profile to interface
clear				Reset functions
.
.
.

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

Router> sh?
* s=show set show slip systat

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

Router> show ?
.
.
.
clock			Display the system clock
dialer			Dialer parameters and statistics
exception			exception information
.
.
.

To redisplay a command that you previously entered, press the Up Arrow key. You can continue to press the Up Arrow key for more commands.

By default, the router ships without password protection. Because many privileged EXEC commands are used to set operating parameters, you should password-protect these commands to prevent unauthorized use.

You can use two commands to do this:

• enable secret password—A very secure, encrypted password.
• enable password—A less secure, unencrypted local password.

Both the enable and enable secret passwords control access to various privilege levels (0 to 15). The enable password is intended for local use and is thus unencrypted. The enable secret password is intended for network use; that is, in environments where the password crosses the network or is stored on a TFTP server. You must enter an enable secret or enable password with a privilege level of 1 to gain access to privileged EXEC mode commands.

For maximum security, the passwords should be different. If you enter the same password for both during the setup process, your router accepts the passwords, but warns you that they should be different.

An enable secret password can contain from 1 to 25 uppercase and lowercase alphanumeric characters. An enable password can contain any number of uppercase and lowercase alphanumeric characters. In both cases, a number cannot be the first character. Spaces are also valid password characters; for example, two words is a valid password. Leading spaces are ignored; trailing spaces are recognized.

1.    After your router boots up, enter the enable or enable secret command:

2.    If you have configured your router with an enable password, enter it when you are prompted.

3.    Enter the configure terminal command to enter global configuration mode:

Router> enable

Password: enable_password
Router#

Router# configure terminal
Router(config)#

This section provides some tips about entering Cisco IOS commands at the command-line interface (CLI).

You must enter the copy running-config startup-config command to save your configuration changes to NVRAM so that they are not lost if there is a system reload or power outage. This example shows how to use this command to save your changes:

Router# copy running-config startup-config
Destination filename [startup-config]?

Press Return to accept the default destination filename startup-config , or enter your desired destination filename and press Return.

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

Building configuration...
Router#

Now that you have reviewed some Cisco IOS software basics, you can begin to configure your router. Remember:

• 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.
• To disable a feature, enter the keyword no before the command; for example, no ip routing.
• Save your configuration changes to NVRAM so that they are not lost if there is a system reload or power outage.