- Preface
- Product Overview
- Basic Router Configuration
- Configuring Ethernet CFM and Y.1731 Performance Monitoring on Layer 3 Interfaces
- Configuring Power Management
- Configuring Security Features
- Configuring Secure Storage
- Configuring Backup Data Lines and Remote Management
- Configuring Ethernet Switches
- Configuring Voice Functionality
- Configuring the Serial Interface
- Configuring Wireless Devices
- Configuring PPP over Ethernet with NAT
- Configuring PPP over ATM with NAT
- Environmental and Power Management
- Configuring a LAN with DHCP and VLANs
- Configuring a VPN Using Easy VPN and an IPSec Tunnel
- Configuring Cisco Multimode G.SHDSL EFM/ATM
- Configuring VDSL2 Bonding and Single-Wire Pair
- Configuring Cisco IOx
- Deployment Scenarios
- Troubleshooting Cisco 800 Series Routers
- Cisco IOS Software Basic Skills
- Concepts
- ROM Monitor
- Index
Cisco IOS Software
Basic Skills
Understanding how to use Cisco IOS software can save you time when you are configuring your router. If you are already familiar with Cisco IOS software, go to one of the following chapters:
This appendix contains the following sections which provide basic information:
- Configuring the Router from a PC
- Understanding Command Modes
- Getting Help
- Enable Secret Passwords and Enable Passwords
- Entering Global Configuration Mode
- Using Commands
- Saving Configuration Changes
- Summary
Configuring the Router from a PC
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.
PC Operating System |
Terminal Emulation Software |
---|---|
Windows 95, Windows 98, Windows 2000, Windows NT, Windows XP |
HyperTerm (included with Windows software), ProComm Plus |
Windows 3.1 |
Terminal (included with Windows software) |
Macintosh |
ProComm, VersaTerm |
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:
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.
Understanding Command Modes
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.
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.
Mode |
Access Method |
Prompt |
Mode Exit and Entrance |
About This Mode |
---|---|---|---|---|
User EXEC |
Begin a session with your router. |
Router> |
To exit a router session, enter the logout command. |
Use this mode to: |
Privileged EXEC |
Enter the enable command from user EXEC mode. |
Router# |
|
Use this mode to:
To prevent unauthorized changes to your router configuration, protect access to this mode by using a password as described in the Enable Secret Passwords and Enable Passwords. |
Global configuration |
Enter the configure command from privileged EXEC mode. |
Router (config)# |
|
Use this mode to configure parameters that apply to your router globally. From this mode you can access the following modes:
|
Interface configuration |
Enter the interface command (with a specific interface, such as interface atm 0) from global configuration mode. |
Router (config-if)# |
|
Use this mode to configure parameters for the router Ethernet and serial interfaces or subinterfaces. |
Router configuration |
Enter one of the router commands followed by the appropriate keyword—for example router rip—from global configuration mode. |
Router (config- router)# |
|
Use this mode to configure an IP routing protocol. |
Line configuration |
Enter the line command with the desired line number and optional line type, for example, line 0, from global configuration mode. |
Router (config- line)# |
|
Use this mode to configure parameters for the terminal line. |
Getting Help
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.
Enable Secret Passwords and Enable Passwords
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.
Entering Global Configuration Mode
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, follow these steps:
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:
DETAILED STEPS
Using Commands
This section provides some tips about entering Cisco IOS commands at the command-line interface (CLI).
Abbreviating Commands
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
Undoing Commands
If you want to disable a feature or undo a command that you entered, you can enter the keyword no before most commands; for example, no ip routing.
Command-Line Error Messages
The table below 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: "show con" |
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 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 the commands that are available in this particular command mode. |
Saving Configuration Changes
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#
Summary
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.
Where to Go Next:
To configure your router, go to Basic Router Configuration, and Deployment Scenarios.