Overview
The initial steps that are used to configure a router are not very difficult. If students become familiar with these steps and learn how to move between the router user modes, it will be easier to perform complex router configurations. This module introduces the basic configuration modes of the router and provides opportunities to practice simple configurations.
A clear, easy to understand router configuration that is backed up regularly should be a goal of all network administrators. The Cisco IOS provides many tools that an administrator can use to add information to the configuration file for documentation purposes. A network administrator should provide as much information as possible in case another person becomes responsible for the network.
This module covers some of the objectives for the CCNA 640-801, INTRO 640-821, and ICND 640-811 exams. -
Students who complete this module should be able to perform the following tasks:
• Name a router
• Set passwords
• Examine show commands
• Configure a serial interface
• Configure an Ethernet interface
• Execute changes to a router
• Save changes to a router
• Configure an interface description
• Configure a message-of-the-day banner
• Configure host tables
• Understand the importance of backups and documentation
Wednesday, May 12, 2010
Sunday, May 2, 2010
Summary
Summary
This page summarizes the topics discussed in this module.
The Cisco IOS is embedded in all Cisco routers. The purpose of the Cisco IOS software is to provide basic routing and switching functions, to give the network scalability, and to provide a reliable and secure way to access the network resources.
The Cisco IOS software uses a command-line interface accessed through a console session or by using a dial-up connection through a modem connected to the router AUX port. A Telnet session to the router can be established remotely if at least one interface is configured with an IP address.
Cisco IOS software provides a command interpreter service known as the command EXEC. After each command is entered, the EXEC validates and executes the command.
There are two access levels available for added security. The user EXEC mode, which is identified by a > prompt, provides basic monitoring commands. From user EXEC mode, a user can run basic commands. For example, the user can view router properties or make temporary changes to the terminal settings. No password is required to access the user EXEC mode.
The privileged EXEC mode, which is identified by a # prompt, is the global configuration and management mode. This mode allows access to all router commands. Within privileged EXEC mode, a user can configure the router interfaces, connect to external sources, load protocols, and move or delete files.
The enable command is used to access privileged EXEC mode. Privileged EXEC mode can also be configured with user name and password for more security.
Enter ? to view a list of available commands in a given mode. If the system detects any errors in a command, a carat symbol (^) will display as a marker. In addition, the enhanced editing mode provides a set of editing key functions that allows the user to edit a command line as it is being typed.
Compatibility issues with the router flash and RAM memory are major considerations before a newer release of the Cisco IOS software can be installed. Use the show version command to check current resources and available memory. Newer releases with more features will typically require more memory. The show flash command is used to verify that the system has sufficient memory to load a new Cisco IOS image. Use of the Cisco Software Advisor provides the most current information and allows the selection of options that meet network requirements.
This page summarizes the topics discussed in this module.
The Cisco IOS is embedded in all Cisco routers. The purpose of the Cisco IOS software is to provide basic routing and switching functions, to give the network scalability, and to provide a reliable and secure way to access the network resources.
The Cisco IOS software uses a command-line interface accessed through a console session or by using a dial-up connection through a modem connected to the router AUX port. A Telnet session to the router can be established remotely if at least one interface is configured with an IP address.
Cisco IOS software provides a command interpreter service known as the command EXEC. After each command is entered, the EXEC validates and executes the command.
There are two access levels available for added security. The user EXEC mode, which is identified by a > prompt, provides basic monitoring commands. From user EXEC mode, a user can run basic commands. For example, the user can view router properties or make temporary changes to the terminal settings. No password is required to access the user EXEC mode.
The privileged EXEC mode, which is identified by a # prompt, is the global configuration and management mode. This mode allows access to all router commands. Within privileged EXEC mode, a user can configure the router interfaces, connect to external sources, load protocols, and move or delete files.
The enable command is used to access privileged EXEC mode. Privileged EXEC mode can also be configured with user name and password for more security.
Enter ? to view a list of available commands in a given mode. If the system detects any errors in a command, a carat symbol (^) will display as a marker. In addition, the enhanced editing mode provides a set of editing key functions that allows the user to edit a command line as it is being typed.
Compatibility issues with the router flash and RAM memory are major considerations before a newer release of the Cisco IOS software can be installed. Use the show version command to check current resources and available memory. Newer releases with more features will typically require more memory. The show flash command is used to verify that the system has sufficient memory to load a new Cisco IOS image. Use of the Cisco Software Advisor provides the most current information and allows the selection of options that meet network requirements.
The show version command
The show version command
2.2.10 This page will discuss the show version command. This command displays information about the Cisco IOS software version that is installed on the router. This includes the configuration register and the boot field settings.
Figure shows the following information from the show version command:
• IOS version and descriptive information
• Bootstrap ROM version
• Boot ROM version
• Router up time
• Last restart method
• System image file and location
• Router platform
• Configuration register setting
Use the show version command to identify a router IOS image and boot source.
This page concludes the lesson on basic router commands. The next page will summarize the main points from this module.
2.2.10 This page will discuss the show version command. This command displays information about the Cisco IOS software version that is installed on the router. This includes the configuration register and the boot field settings.
Figure shows the following information from the show version command:
• IOS version and descriptive information
• Bootstrap ROM version
• Boot ROM version
• Router up time
• Last restart method
• System image file and location
• Router platform
• Configuration register setting
Use the show version command to identify a router IOS image and boot source.
This page concludes the lesson on basic router commands. The next page will summarize the main points from this module.
Troubleshooting command line errors
Troubleshooting command line errors
2.2.9 This page will show students how to locate and fix command line errors.
Command line errors occur primarily from typing mistakes. If a command keyword is incorrectly typed, the user interface uses the caret symbol (^) to identify and isolate the error. The ^ appears at the point in the command string where an incorrect command, keyword, or argument was entered. The error location indicator and interactive help system allow the user to easily find and correct syntax errors.
Router#clock set 13:32:00 23 February
99
^
% Invalid input detected at '^' marker.
The caret symbol (^) and help response indicate an error at 99. To list the correct syntax, enter the command up to the point where the error occurred and then enter a question mark (?):
Router#clock set 13:32:00 23 February ?
<1993-2035> Year
Router#clock set 13:32:00 23 February
Use the correct syntax to add the year and press Enter or Return to execute the command.
Router#clock set 13:32:00 23 February 1999
If a command line is entered incorrectly, and the Enter key is pressed, the Up Arrow can be pressed to repeat the last command. Use the Right Arrow and Left Arrow keys to move the cursor to the location where the mistake was made. Then make the correction. If something needs to be deleted, use the Backspace key.
The next page will discuss the show version command.
2.2.9 This page will show students how to locate and fix command line errors.
Command line errors occur primarily from typing mistakes. If a command keyword is incorrectly typed, the user interface uses the caret symbol (^) to identify and isolate the error. The ^ appears at the point in the command string where an incorrect command, keyword, or argument was entered. The error location indicator and interactive help system allow the user to easily find and correct syntax errors.
Router#clock set 13:32:00 23 February
99
^
% Invalid input detected at '^' marker.
The caret symbol (^) and help response indicate an error at 99. To list the correct syntax, enter the command up to the point where the error occurred and then enter a question mark (?):
Router#clock set 13:32:00 23 February ?
<1993-2035> Year
Router#clock set 13:32:00 23 February
Use the correct syntax to add the year and press Enter or Return to execute the command.
Router#clock set 13:32:00 23 February 1999
If a command line is entered incorrectly, and the Enter key is pressed, the Up Arrow can be pressed to repeat the last command. Use the Right Arrow and Left Arrow keys to move the cursor to the location where the mistake was made. Then make the correction. If something needs to be deleted, use the Backspace key.
The next page will discuss the show version command.
Router command history
Router command history
2.2.8 The user interface provides a history or record of commands that have been entered. This page will explain the use and benefits of this feature. This feature is particularly useful for recalling long or complex commands or entries. The command history feature can be used to perform the following tasks:
• Set the command history buffer size
• Recall commands
• Disable the command history feature
The command history is enabled by default and the system records ten command lines in its history buffer. To change the number of command lines the system records during a terminal session, use the terminal history size or the history size command. The maximum number of commands is 256.
To recall the most recent command in the history buffer, press Ctrl-P or the Up Arrow key. Repeat this process to recall successively older commands. To return to a more recent command in the history buffer, press Ctrl-N or the Down Arrow key. Repeat this process to recall successively more recent commands.
When typing commands, as a shortcut, the unique characters may be entered for a command. Press the Tab key, and the interface will finish the entry. When the typed letters uniquely identify the command, the Tab key simply acknowledges visually that the router has understood the specific command that was intended.
On most computers additional select and copy functions are available. A previous command string may be copied and then pasted or inserted as the current command entry.
The next page will teach students how to troubleshoot command line errors.
2.2.8 The user interface provides a history or record of commands that have been entered. This page will explain the use and benefits of this feature. This feature is particularly useful for recalling long or complex commands or entries. The command history feature can be used to perform the following tasks:
• Set the command history buffer size
• Recall commands
• Disable the command history feature
The command history is enabled by default and the system records ten command lines in its history buffer. To change the number of command lines the system records during a terminal session, use the terminal history size or the history size command. The maximum number of commands is 256.
To recall the most recent command in the history buffer, press Ctrl-P or the Up Arrow key. Repeat this process to recall successively older commands. To return to a more recent command in the history buffer, press Ctrl-N or the Down Arrow key. Repeat this process to recall successively more recent commands.
When typing commands, as a shortcut, the unique characters may be entered for a command. Press the Tab key, and the interface will finish the entry. When the typed letters uniquely identify the command, the Tab key simply acknowledges visually that the router has understood the specific command that was intended.
On most computers additional select and copy functions are available. A previous command string may be copied and then pasted or inserted as the current command entry.
The next page will teach students how to troubleshoot command line errors.
Enhanced editing commands
Enhanced editing commands
2.2.7 This page will introduce the enhanced editing mode that is available in the Cisco IOS user interface. This mode provides a set of editing key functions that allows a user to edit a command line as it is being typed.
The key sequences indicated in Figure can be used to move the cursor on the command line for corrections or changes. Although enhanced editing mode is automatically enabled with the current software release, it can be disabled if it interferes with the interaction of written scripts. To disable enhanced editing mode, type terminal no editing at the privileged EXEC mode prompt.
The editing command set provides a horizontal scrolling feature for commands that extend beyond a single line on the screen. When the cursor reaches the right margin, the command line shifts ten spaces to the left. The first ten characters of the line cannot be seen, but a user can scroll back and check the syntax at the beginning of the command. To scroll back, press Ctrl-B or the Left Arrow key repeatedly until the beginning of the command entry is reached. Ctrl-A will return a user directly to the beginning of the line.
In the example shown in Figure , the command entry extends beyond one line. When the cursor first reaches the end of the line, the line is shifted ten spaces to the left and redisplayed. The dollar sign ($) indicates that the line has been scrolled to the left. Each time the cursor reaches the end of the line, the line is again shifted ten spaces to the left.
Ctrl-Z is a command used to back out of configuration mode. This will return the user to the privileged EXEC mode prompt.
The next page will introduce the Cisco IOS command history feature.
2.2.7 This page will introduce the enhanced editing mode that is available in the Cisco IOS user interface. This mode provides a set of editing key functions that allows a user to edit a command line as it is being typed.
The key sequences indicated in Figure can be used to move the cursor on the command line for corrections or changes. Although enhanced editing mode is automatically enabled with the current software release, it can be disabled if it interferes with the interaction of written scripts. To disable enhanced editing mode, type terminal no editing at the privileged EXEC mode prompt.
The editing command set provides a horizontal scrolling feature for commands that extend beyond a single line on the screen. When the cursor reaches the right margin, the command line shifts ten spaces to the left. The first ten characters of the line cannot be seen, but a user can scroll back and check the syntax at the beginning of the command. To scroll back, press Ctrl-B or the Left Arrow key repeatedly until the beginning of the command entry is reached. Ctrl-A will return a user directly to the beginning of the line.
In the example shown in Figure , the command entry extends beyond one line. When the cursor first reaches the end of the line, the line is shifted ten spaces to the left and redisplayed. The dollar sign ($) indicates that the line has been scrolled to the left. Each time the cursor reaches the end of the line, the line is again shifted ten spaces to the left.
Ctrl-Z is a command used to back out of configuration mode. This will return the user to the privileged EXEC mode prompt.
The next page will introduce the Cisco IOS command history feature.
Keyboard help in the router CLI
Keyboard help in the router CLI
2.2.6 This page will introduce some router help functions.
A question mark, ?, can be entered at the user EXEC or privileged EXEC mode prompt to display a list of available commands. Notice the --More-- at the bottom of the display in Figure . The --More-- prompt indicates that there are multiple screens of output. When a --More-- prompt appears, press the Spacebar to view the next available screen. To display just the next line, press the Return or Enter key. Press any other key to return to the prompt.
To access privileged EXEC mode, type enable or the abbreviation en or ena. This might cause the router to prompt the user for a password if one has been set. Figure lists the commands that are available in privileged EXEC mode.
Screen output varies, depending on Cisco IOS software level and router configuration.
The help function, or question mark, ?, can be used to display the commands that are used to perform certain tasks. The following exercise illustrates one of the many uses of the help function.
If a user wants to set the router clock and does not know the command, the help function can be used as follows:
1. Use ? to find the command for setting the clock. The help output shows that the clock command is required.
2. Check the syntax for changing the time.
3. Enter the current time by using hours, minutes, and seconds, as shown in Figure . The system indicates that additional information needs to be provided to complete the command.
4. Press Ctrl-P or the Up Arrow to repeat the previous command entry. Then add a space and a question mark (?) to reveal the additional arguments. Now the command entry can be completed.
5. The caret symbol (^) and help response indicate an error. The placement of the caret symbol shows where the possible problem is located. To input the correct syntax, re-enter the command up to the point where the caret symbol is located and then enter a question mark (?).
6. Enter the year, using the correct syntax, and press Return or Enter to execute the command.
As demonstrated in the IOS Auto-Completion e-Lab, typing an abbreviated command, such as sh, followed by the Tab key completes a partial command name.
The next page will introduce some enhanced editing commands that are available in the Cisco IOS.
2.2.6 This page will introduce some router help functions.
A question mark, ?, can be entered at the user EXEC or privileged EXEC mode prompt to display a list of available commands. Notice the --More-- at the bottom of the display in Figure . The --More-- prompt indicates that there are multiple screens of output. When a --More-- prompt appears, press the Spacebar to view the next available screen. To display just the next line, press the Return or Enter key. Press any other key to return to the prompt.
To access privileged EXEC mode, type enable or the abbreviation en or ena. This might cause the router to prompt the user for a password if one has been set. Figure lists the commands that are available in privileged EXEC mode.
Screen output varies, depending on Cisco IOS software level and router configuration.
The help function, or question mark, ?, can be used to display the commands that are used to perform certain tasks. The following exercise illustrates one of the many uses of the help function.
If a user wants to set the router clock and does not know the command, the help function can be used as follows:
1. Use ? to find the command for setting the clock. The help output shows that the clock command is required.
2. Check the syntax for changing the time.
3. Enter the current time by using hours, minutes, and seconds, as shown in Figure . The system indicates that additional information needs to be provided to complete the command.
4. Press Ctrl-P or the Up Arrow to repeat the previous command entry. Then add a space and a question mark (?) to reveal the additional arguments. Now the command entry can be completed.
5. The caret symbol (^) and help response indicate an error. The placement of the caret symbol shows where the possible problem is located. To input the correct syntax, re-enter the command up to the point where the caret symbol is located and then enter a question mark (?).
6. Enter the year, using the correct syntax, and press Return or Enter to execute the command.
As demonstrated in the IOS Auto-Completion e-Lab, typing an abbreviated command, such as sh, followed by the Tab key completes a partial command name.
The next page will introduce some enhanced editing commands that are available in the Cisco IOS.
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