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Understanding how to use Cisco IOS software saves time when you are configuring your router. If you need a refresher, take a few minutes to read this chapter. If you are already familiar with Cisco IOS software, go to "Feature-By-Feature Router Configurations."
This chapter describes what you need to know before you begin configuring your Cisco 827 router with Cisco IOS software (the software that runs your router).
This chapter contains the following sections:
You can configure your router from a connected PC. For information on how to connect the PC, refer to the Cisco 827 Routers Hardware Installation Guide.
After connecting the PC, you need terminal emulation software. The PC uses this software to send commands to your router. Table A-1 lists some common types of this software, which are based on the type of PC you are using.
| PC Operating System | Software |
|---|---|
Windows 95, Windows 98, Windows NT | HyperTerm (included with Windows software), ProComm Plus |
Windows 3.1 | Terminal (included with Windows software) |
Macintosh | ProComm, VersaTerm (supplied separately) |
You can use the terminal emulation software to change settings for the type of device that is connected to the PC, in this case a router. Configure the software to the following standard VT-100 emulation settings so that your PC can communicate with your router:
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, refer to "ROM Monitor." To change the router flow control setting, use the flowcontrol line configuration command.
For information on how to enter global configuration mode so that you can configure your router, refer to 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.
Table A-2 lists the command modes that are used in this guide, how to access each mode, the prompt you see in that mode, and how to exit to a mode or enter the next 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, refer to the Cisco IOS 12.0 documentation set.
| Mode | Access Method | Prompt | Exit/Entrance Method | About this Mode |
|---|---|---|---|---|
Begin a session with your router. | Router> | To exit router session, enter the logout command. | Use this mode to:
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Enter the enable command from user EXEC mode. | Router# | To exit to user EXEC mode, enter the disable command. To enter global configuration mode, enter the configure command. | Use this mode to:
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Enter the configure command from privileged EXEC mode. | Router | To exit to privileged EXEC mode, enter the exit or end command, or press Ctrl-Z. To enter interface configuration mode, enter the interface command. | Use this mode to configure parameters that apply to your router as a whole. Also, you can access the following modes, which are described later in this table:
| |
Enter the interface command (with a specific interface, such as interface ethernet 0) from global configuration mode. | Router | To exit to global configuration mode, enter the exit command. To exit to privileged EXEC mode, enter the end command, or press Ctrl-Z. To enter subinterface configuration mode, specify a subinterface with the interface command. | Use this mode to configure parameters for the router Ethernet and serial interfaces or subinterfaces. | |
Enter your router command followed by the appropriate keyword, for example router rip, from global configuration mode. | Router (config- | To exit to global configuration mode, enter the exit command. To exit to privileged EXEC mode, enter the end command, or press Ctrl-Z. | Use this mode to configure an IP routing protocol. | |
Specify the line command with the desired keyword, for example, line 0, from global configuration mode. | Router (config- | To exit to global configuration mode, enter the exit command. To enter privileged EXEC mode, enter the end command, or press Ctrl-Z. | Use this mode to configure parameters for the terminal line. |
You can use the question mark (?) and arrow keys to help you enter commands.
For a list of available commands at that 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> s? * 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 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:
You must enter an enable secret password 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.
To make any configuration changes to your router, you must be in global configuration mode. This section describes how to enter global configuration mode while using a terminal or PC that is connected to your router console port.
To enter global configuration mode:
Step 1 After your router boots up, answer no when the following question displays:
Would you like to enter the initial configuration dialog [yes]: no
Step 2 Enter the enable command:
router> enable
Step 3 If you have configured your router with an enable password, enter it when you are prompted.
The enable password does not show on the screen when you enter it. This example shows how to enter privileged EXEC mode:
Password: enable_password router#
Enable mode is indicated by the # in the prompt. You can now make changes to your router configuration.
Step 4 Enter the configure terminal command to enter global configuration mode, indicated by (config)# in the prompt:
router# configure terminal router (config)#
You can now make changes to your router configuration.
This section provides some tips about entering Cisco IOS commands at the command-line interface (CLI).
You only have to enter enough characters for the router to recognize the command as unique. This example shows how to enter the show version command:
router # sh v
If you want to disable a feature or undo a command you entered, you can enter the keyword no before most commands; for example, no ip routing.
Table A-3 lists some error messages that you might encounter while using the CLI to configure your router.
| Error Message | Meaning | How to Get Help |
|---|---|---|
% Ambiguous command: | You did not enter enough characters for your router to recognize the command. | Reenter the command followed by a question mark (?) with no space between the command and the question mark. The possible keywords that you can enter with the command are displayed. |
% Incomplete command. | You did not enter all of the keywords or values required by this command. | Reenter the command followed by a question mark (?) with no space between the command and the question mark. The possible keywords that you can enter with the command are displayed. |
% Invalid input detected at `^' marker. | You entered the command incorrectly. The error occurred where the caret mark (^) appears. | Enter a question mark (?) to display all of the commands that are available in this command mode. |
You need to enter the copy running-config startup-config command to save your configuration changes to nonvolatile RAM (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:
To configure your router, go to Chapter 3, "Feature-By-Feature Router Configurations."
Posted: Fri Apr 7 14:58:19 PDT 2000
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