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.
Sunday, May 2, 2010
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.
Router login
Router login
2.2.5 To enter commands and configure a Cisco router, a user must log into the router to access the user interface. This page will show students how to log into a router.
For security purposes, a Cisco router has two levels of access to commands:
• User EXEC mode – Typical tasks include commands that check the status of a router.
• Privileged EXEC mode –Typical tasks include commands that change the router configuration.
The user EXEC mode prompt is displayed upon login to a router, as shown in Figure .
To enter privileged EXEC mode, type enable at the > prompt. If a password has been set, enter it at the password: prompt. The two commands that can be used to set a password for privileged EXEC mode are enable password and enable secret. Two commands can be used to set a password used to access privileged EXEC mode: enable password and enable secret. If both commands are used, the enable secret command takes precedence. After the login steps have been completed, the prompt changes to a #. This indicates that the privileged EXEC mode has been entered. The global configuration mode can only be accessed from the privileged EXEC mode. The following are specific modes that can also be accessed from the global configuration mode:
• Interface
• Subinterface
• Line
• Router
• Route-map
To return to the user EXEC mode from the privileged EXEC mode, the disable command may be entered. Type exit or end or press Ctrl-Z to return to privileged EXEC mode from global configuration mode. Ctrl-Z may also be used to return directly to the privileged EXEC mode from any sub-mode of global configuration.
The next page covers some help functions of the Cisco IOS.
2.2.5 To enter commands and configure a Cisco router, a user must log into the router to access the user interface. This page will show students how to log into a router.
For security purposes, a Cisco router has two levels of access to commands:
• User EXEC mode – Typical tasks include commands that check the status of a router.
• Privileged EXEC mode –Typical tasks include commands that change the router configuration.
The user EXEC mode prompt is displayed upon login to a router, as shown in Figure .
To enter privileged EXEC mode, type enable at the > prompt. If a password has been set, enter it at the password: prompt. The two commands that can be used to set a password for privileged EXEC mode are enable password and enable secret. Two commands can be used to set a password used to access privileged EXEC mode: enable password and enable secret. If both commands are used, the enable secret command takes precedence. After the login steps have been completed, the prompt changes to a #. This indicates that the privileged EXEC mode has been entered. The global configuration mode can only be accessed from the privileged EXEC mode. The following are specific modes that can also be accessed from the global configuration mode:
• Interface
• Subinterface
• Line
• Router
• Route-map
To return to the user EXEC mode from the privileged EXEC mode, the disable command may be entered. Type exit or end or press Ctrl-Z to return to privileged EXEC mode from global configuration mode. Ctrl-Z may also be used to return directly to the privileged EXEC mode from any sub-mode of global configuration.
The next page covers some help functions of the Cisco IOS.
Establish a console session
Establish a console session
2.2.4 This page will explain how a console session is established with a router.
All Cisco routers include a TIA/EIA-232 asynchronous serial console port. The console port is an RJ-45. Cables and adapters are needed to connect a console terminal to the console port. A console terminal is an ASCII terminal or PC that runs terminal-emulation software such as HyperTerminal. Use an RJ-45 to RJ-45 rollover cable with a female RJ-45 to DB-9 adapter to connect this type of a PC to the console port.
The default parameters for the console port are 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control. The console port does not support hardware flow control.
Take the following steps to connect a terminal to the console port on a router:
1. Connect the terminal using the RJ-45 to RJ-45 rollover cable and an RJ-45 to DB-9 adapter.
2. Configure the terminal or PC terminal emulation software for 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control.
The next page will teach students how to log into a router.
2.2.4 This page will explain how a console session is established with a router.
All Cisco routers include a TIA/EIA-232 asynchronous serial console port. The console port is an RJ-45. Cables and adapters are needed to connect a console terminal to the console port. A console terminal is an ASCII terminal or PC that runs terminal-emulation software such as HyperTerminal. Use an RJ-45 to RJ-45 rollover cable with a female RJ-45 to DB-9 adapter to connect this type of a PC to the console port.
The default parameters for the console port are 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control. The console port does not support hardware flow control.
Take the following steps to connect a terminal to the console port on a router:
1. Connect the terminal using the RJ-45 to RJ-45 rollover cable and an RJ-45 to DB-9 adapter.
2. Configure the terminal or PC terminal emulation software for 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control.
The next page will teach students how to log into a router.
Router LED indicators/The initial router bootup
Router LED indicators
2.2.2 This page will explain how routers use LED indicators.
Cisco routers use LED indicators to provide status information. LED indicators will vary for different Cisco router models.
An interface LED indicates the activity of the corresponding interface. A problem may be indicated if an LED is off when the interface is active and the interface is correctly connected. If an interface is extremely busy, its LED will always be on. The green OK LED to the right of the AUX port will be on after the system initializes correctly.
The next page will examine the initial router bootup
The initial router bootup
2.2.3 This page will discuss the information and messages that are displayed during the initial router bootup. This information will vary, depending on the interfaces in the router and the Cisco IOS release. The screens displayed on this page are for reference only and may not reflect what the screen displays on the console.
In Figure , the statement “NVRAM invalid, possibly due to write erase”, tells the user that this router has not been configured yet or that the NVRAM has been erased. In order for the NVRAM to be valid after a router is configured and the configuration file is saved to NVRAM, the router must be configured to use the NVRAM configuration file. The factory-default setting for the configuration register is 0x2102, which indicates that the router should attempt to load a Cisco IOS image from flash memory.
In Figure , the user can determine the bootstrap version and the IOS version the router is using as well as the router model, processor, and the amount of memory the router contains. The figure also includes the following information:
• The number of interfaces
• The types of interfaces
• The amount of NVRAM
• The amount of flash memory
In Figure , the user has the option to enter setup mode. Remember, the primary purpose of the setup mode is to permit an administrator to install a basic router configuration when it cannot be obtained from another source.
The next page will teach students how to establish a console session with a router.
2.2.2 This page will explain how routers use LED indicators.
Cisco routers use LED indicators to provide status information. LED indicators will vary for different Cisco router models.
An interface LED indicates the activity of the corresponding interface. A problem may be indicated if an LED is off when the interface is active and the interface is correctly connected. If an interface is extremely busy, its LED will always be on. The green OK LED to the right of the AUX port will be on after the system initializes correctly.
The next page will examine the initial router bootup
The initial router bootup
2.2.3 This page will discuss the information and messages that are displayed during the initial router bootup. This information will vary, depending on the interfaces in the router and the Cisco IOS release. The screens displayed on this page are for reference only and may not reflect what the screen displays on the console.
In Figure , the statement “NVRAM invalid, possibly due to write erase”, tells the user that this router has not been configured yet or that the NVRAM has been erased. In order for the NVRAM to be valid after a router is configured and the configuration file is saved to NVRAM, the router must be configured to use the NVRAM configuration file. The factory-default setting for the configuration register is 0x2102, which indicates that the router should attempt to load a Cisco IOS image from flash memory.
In Figure , the user can determine the bootstrap version and the IOS version the router is using as well as the router model, processor, and the amount of memory the router contains. The figure also includes the following information:
• The number of interfaces
• The types of interfaces
• The amount of NVRAM
• The amount of flash memory
In Figure , the user has the option to enter setup mode. Remember, the primary purpose of the setup mode is to permit an administrator to install a basic router configuration when it cannot be obtained from another source.
The next page will teach students how to establish a console session with a router.
Initial startup of Cisco routers
Initial startup of Cisco routers
2.2.1 This page will explain the startup process for Cisco routers.
A router initializes by loading the bootstrap, the operating system, and a configuration file. If the router cannot find a configuration file, it enters setup mode. Upon completion of the setup mode, a backup copy of the configuration file may be saved to NVRAM.
The goal of the startup routines for Cisco IOS software is to start the router operations. To do this, the startup routines must accomplish the following:
• Verify that the router hardware is tested and functional.
• Find and load the Cisco IOS software.
• Find and apply the startup configuration file or enter the setup mode.
When a Cisco router powers up, it performs a power-on self test (POST). During this self test, the router executes diagnostics from ROM on all hardware modules. These diagnostics verify the basic operation of the CPU, memory, and network interface ports. After verifying the hardware functions, the router proceeds with software initialization.
After the POST, the following events occur as the router initializes:
1. The generic bootstrap loader in ROM executes. A bootstrap is a simple set of instructions that tests hardware and initializes the IOS for operation.
2. The IOS can be found in several places. The boot field of the configuration register determines the location that is used to load the IOS. If the boot field indicates a flash or network load, boot system commands in the configuration file indicate the exact name and location of the image.
3. The operating system image is loaded. When the IOS is loaded and operational, a listing of the available hardware and software components is sent to the console terminal screen.
4. The configuration file saved in NVRAM is loaded into main memory and executed one line at a time. The configuration commands start routing processes, supply addresses for interfaces, and define other operating characteristics of the router.
5. If no valid configuration file exists in NVRAM, the operating system searches for an available TFTP server. If no TFTP server is found, the setup dialog is initiated.
Setup mode is not intended to be used to enter complex protocol features in a router. The purpose of the setup mode is to permit administrators to install a basic configuration for routers when a configuration cannot be obtained from another source.
In the setup mode, default answers appear in square brackets [ ] following the question. Press the Enter key to use these defaults. During the setup process, Ctrl-C can be pressed at any time to terminate the process. When Ctrl-C is used to terminate setup, all interfaces are administratively shut down.
When the configuration process is completed in setup mode, the following options will be displayed:
[0] Go to the IOS command prompt without saving this config.
[1] Return back to the setup without saving this config.
[2] Save this configuration to nvram and exit. Enter your selection [2]:
The next page will discuss router LED indicators.
2.2.1 This page will explain the startup process for Cisco routers.
A router initializes by loading the bootstrap, the operating system, and a configuration file. If the router cannot find a configuration file, it enters setup mode. Upon completion of the setup mode, a backup copy of the configuration file may be saved to NVRAM.
The goal of the startup routines for Cisco IOS software is to start the router operations. To do this, the startup routines must accomplish the following:
• Verify that the router hardware is tested and functional.
• Find and load the Cisco IOS software.
• Find and apply the startup configuration file or enter the setup mode.
When a Cisco router powers up, it performs a power-on self test (POST). During this self test, the router executes diagnostics from ROM on all hardware modules. These diagnostics verify the basic operation of the CPU, memory, and network interface ports. After verifying the hardware functions, the router proceeds with software initialization.
After the POST, the following events occur as the router initializes:
1. The generic bootstrap loader in ROM executes. A bootstrap is a simple set of instructions that tests hardware and initializes the IOS for operation.
2. The IOS can be found in several places. The boot field of the configuration register determines the location that is used to load the IOS. If the boot field indicates a flash or network load, boot system commands in the configuration file indicate the exact name and location of the image.
3. The operating system image is loaded. When the IOS is loaded and operational, a listing of the available hardware and software components is sent to the console terminal screen.
4. The configuration file saved in NVRAM is loaded into main memory and executed one line at a time. The configuration commands start routing processes, supply addresses for interfaces, and define other operating characteristics of the router.
5. If no valid configuration file exists in NVRAM, the operating system searches for an available TFTP server. If no TFTP server is found, the setup dialog is initiated.
Setup mode is not intended to be used to enter complex protocol features in a router. The purpose of the setup mode is to permit administrators to install a basic configuration for routers when a configuration cannot be obtained from another source.
In the setup mode, default answers appear in square brackets [ ] following the question. Press the Enter key to use these defaults. During the setup process, Ctrl-C can be pressed at any time to terminate the process. When Ctrl-C is used to terminate setup, all interfaces are administratively shut down.
When the configuration process is completed in setup mode, the following options will be displayed:
[0] Go to the IOS command prompt without saving this config.
[1] Return back to the setup without saving this config.
[2] Save this configuration to nvram and exit. Enter your selection [2]:
The next page will discuss router LED indicators.
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