Configuring an interface description
3.2.3 This page will teach students how to configure an interface description.
To configure an interface description, enter global configuration mode. From global configuration mode, enter interface configuration mode. Use the command description followed by the information.
The steps to configure an interface description are as follows:
1. Use the configure terminal command to enter global configuration mode.
2. Enter a specific interface mode such as interface ethernet 0.
3. Enter the command description followed by the information that is to be displayed, such as XYZ Network, Building 18.
4. Use Ctrl-Z to exit interface mode and return to privileged EXEC mode.
5. Use the copy running-config startup-config command to save the configuration changes to NVRAM.
Here are two examples of interface descriptions:
interface ethernet 0
description LAN Engineering, Bldg.2
interface serial 0
description ABC network 1, Circuit 1
The next page will describe login banners.
Wednesday, May 12, 2010
Interface descriptions
Interface descriptions
3.2.2 This page will explain what interface descriptions are and why they are used.
An interface description should identify important information such as a router, a circuit number, or a specific network segment. A description of an interface can help a network user remember specific information about the interface, such as what network the interface services.
The description will appear in the configuration files that exist in the router memory. However, it will not affect the operation of a router. A description only provides information about an interface. Descriptions are created by following a standard format that applies to each interface. The description may include the purpose and location of the interface, other devices or locations connected to the interface, and circuit identifiers. Descriptions allow support personnel to better understand the scope of problems related to an interface and allow for faster resolution of problems.
The next page will describe how interface descriptions are configured.
3.2.2 This page will explain what interface descriptions are and why they are used.
An interface description should identify important information such as a router, a circuit number, or a specific network segment. A description of an interface can help a network user remember specific information about the interface, such as what network the interface services.
The description will appear in the configuration files that exist in the router memory. However, it will not affect the operation of a router. A description only provides information about an interface. Descriptions are created by following a standard format that applies to each interface. The description may include the purpose and location of the interface, other devices or locations connected to the interface, and circuit identifiers. Descriptions allow support personnel to better understand the scope of problems related to an interface and allow for faster resolution of problems.
The next page will describe how interface descriptions are configured.
Importance of configuration standards
Importance of configuration standards
3.2.1 This page explains why it is important to develop standards for configuration files within an organization.
Configuration standards can be used to control of the number of configuration files that must be maintained, how the files are stored, and where the files are stored.
A standard is a set of rules or procedures that are either widely used or officially specified. If an organization does not have standards, the network will be in chaos if a service interruption occurs.
Network management requires a centralized support standard. Configuration, security, performance, and other issues must be addressed for the network to function properly. The creation of standards for network consistency helps reduce network complexity, unplanned downtime, and events that may affect network performance.
The next page will discuss interface descriptions.
3.2.1 This page explains why it is important to develop standards for configuration files within an organization.
Configuration standards can be used to control of the number of configuration files that must be maintained, how the files are stored, and where the files are stored.
A standard is a set of rules or procedures that are either widely used or officially specified. If an organization does not have standards, the network will be in chaos if a service interruption occurs.
Network management requires a centralized support standard. Configuration, security, performance, and other issues must be addressed for the network to function properly. The creation of standards for network consistency helps reduce network complexity, unplanned downtime, and events that may affect network performance.
The next page will discuss interface descriptions.
Configuring an Ethernet interface
Configuring an Ethernet interface
3.1.7 This page will explain how an Ethernet interface can be configured from the console or a virtual terminal line.
Each Ethernet interface must have an IP address and subnet mask to route IP packets.
To configure an Ethernet interface follow these steps:
1. Enter global configuration mode.
2. Enter interface configuration mode.
3. Specify the interface address and subnet mask.
4. Enable the interface.
By default, interfaces are turned off, or disabled. To turn on or enable an interface, the command no shutdown is entered. If an interface needs to be disabled for maintenance or troubleshooting, use the shutdown command to turn off the interface.
This page concludes this lesson. The next lesson will explain how a configuration is finalized. The first page covers the importance of configuration standards.
3.1.7 This page will explain how an Ethernet interface can be configured from the console or a virtual terminal line.
Each Ethernet interface must have an IP address and subnet mask to route IP packets.
To configure an Ethernet interface follow these steps:
1. Enter global configuration mode.
2. Enter interface configuration mode.
3. Specify the interface address and subnet mask.
4. Enable the interface.
By default, interfaces are turned off, or disabled. To turn on or enable an interface, the command no shutdown is entered. If an interface needs to be disabled for maintenance or troubleshooting, use the shutdown command to turn off the interface.
This page concludes this lesson. The next lesson will explain how a configuration is finalized. The first page covers the importance of configuration standards.
Making configuration changes
Making configuration changes
3.1.6 This page will explain how configuration variables can be changed in different modes.
If a configuration requires modification, go to the appropriate mode and enter the proper command. For example, if an interface must be enabled, enter global configuration mode, enter interface mode, and issue the command no shutdown.
To verify changes, use the show running-config command. This command will display the current configuration. If the variables displayed are not correct, the environment can be changed in the following ways:
• Issue the no form of a configuration command.
• Reload the system to return to the original configuration file from NVRAM.
• Copy an archived configuration file from a TFTP server.
• Remove the startup configuration file with the erase startup-config, then restart the router and enter setup mode.
To save the configuration variables to the startup configuration file in NVRAM, enter the following command at the privileged EXEC prompt:
Router#copy running-config startup-config
The next page will teach students how to configure an Ethernet interface
3.1.6 This page will explain how configuration variables can be changed in different modes.
If a configuration requires modification, go to the appropriate mode and enter the proper command. For example, if an interface must be enabled, enter global configuration mode, enter interface mode, and issue the command no shutdown.
To verify changes, use the show running-config command. This command will display the current configuration. If the variables displayed are not correct, the environment can be changed in the following ways:
• Issue the no form of a configuration command.
• Reload the system to return to the original configuration file from NVRAM.
• Copy an archived configuration file from a TFTP server.
• Remove the startup configuration file with the erase startup-config, then restart the router and enter setup mode.
To save the configuration variables to the startup configuration file in NVRAM, enter the following command at the privileged EXEC prompt:
Router#copy running-config startup-config
The next page will teach students how to configure an Ethernet interface
Configuring a serial interface
Configuring a serial interface
3.1.5 This page will explain how a serial interface can be configured from the console or through a virtual terminal line. To configure a serial interface follow these steps:
1. Enter global configuration mode.
2. Enter interface mode.
3. Specify the interface address and subnet mask.
4. Set clock rate if a DCE cable is connected. Skip this step if a DTE cable is connected.
5. Turn on the interface.
Each connected serial interface must have an IP address and subnet mask to route IP packets. Configure the IP address with the following commands:
Router(config)#interface serial 0/0
Router(config-if)#ip address
Serial interfaces require a clock signal to control the timing of the communications. In most environments, a DCE device such as a CSU/DSU will provide the clock. By default, Cisco routers are DTE devices but they can be configured as DCE devices.
On serial links that are directly interconnected, as in a lab environment, one side must be considered a DCE and provide a clocking signal. The clock is enabled and speed is specified with the clock rate command. The available clock rates in bits per second are 1200, 2400, 9600, 19200, 38400, 56000, 64000, 72000, 125000, 148000, 500000, 800000, 1000000, 1300000, 2000000, or 4000000. Some bit rates might not be available on certain serial interfaces. This depends on the capacity of each interface.
By default, interfaces are turned off, or disabled. To turn on or enable an interface, the command no shutdown is entered. If an interface needs to be administratively disabled for maintenance or troubleshooting, the shutdown command used to turn off the interface.
In the lab environment, the clockrate setting that will be used is 56000. The commands that are used to set a clock rate and enable a serial interface are as follows:
Router(config)#interface serial 0/0
Router(config-if)#clock rate 56000
Router(config-if)#no shutdown
The next page will teach students how to change configurations.
3.1.5 This page will explain how a serial interface can be configured from the console or through a virtual terminal line. To configure a serial interface follow these steps:
1. Enter global configuration mode.
2. Enter interface mode.
3. Specify the interface address and subnet mask.
4. Set clock rate if a DCE cable is connected. Skip this step if a DTE cable is connected.
5. Turn on the interface.
Each connected serial interface must have an IP address and subnet mask to route IP packets. Configure the IP address with the following commands:
Router(config)#interface serial 0/0
Router(config-if)#ip address
Serial interfaces require a clock signal to control the timing of the communications. In most environments, a DCE device such as a CSU/DSU will provide the clock. By default, Cisco routers are DTE devices but they can be configured as DCE devices.
On serial links that are directly interconnected, as in a lab environment, one side must be considered a DCE and provide a clocking signal. The clock is enabled and speed is specified with the clock rate command. The available clock rates in bits per second are 1200, 2400, 9600, 19200, 38400, 56000, 64000, 72000, 125000, 148000, 500000, 800000, 1000000, 1300000, 2000000, or 4000000. Some bit rates might not be available on certain serial interfaces. This depends on the capacity of each interface.
By default, interfaces are turned off, or disabled. To turn on or enable an interface, the command no shutdown is entered. If an interface needs to be administratively disabled for maintenance or troubleshooting, the shutdown command used to turn off the interface.
In the lab environment, the clockrate setting that will be used is 56000. The commands that are used to set a clock rate and enable a serial interface are as follows:
Router(config)#interface serial 0/0
Router(config-if)#clock rate 56000
Router(config-if)#no shutdown
The next page will teach students how to change configurations.
Examining the show commands
Examining the show commands
3.1.4 This page will introduce some show commands. Many of these commands can be used to examine the contents of files in the router and for troubleshooting. In both privileged EXEC and user EXEC modes, the command show ? provides a list of available show commands. The list is considerably longer in privileged EXEC mode than it is in user EXEC mode.
Students should learn the functions of the following commands:
• show interfaces – Displays statistics for all interfaces on a router. To view the statistics for a specific interface, enter the show interfaces command followed by the specific interface slot/port number. This is shown in the following example:
Router#show interfaces serial 0/1
• show controllers serial - Displays information that is specific to the interface hardware. This command must also include the port or slot/port number of the serial interface. For example:
Router#show controllers serial 0/1
• show clock - Shows the time set in the router
• show hosts - Displays a cached list of host names and addresses
• show users - Displays all users who are connected to the router
• show history - Displays a history of commands that have been entered
• show flash - Displays information about flash memory and what IOS files are stored there
• show version - Displays information about the currently loaded software version along with hardware and device information.
• show arp - Displays the ARP table of the router
• show protocols - Displays the global and interface-specific status of any configured Layer 3 protocols
• show startup-config - Displays the saved configuration located in NVRAM
• show running-config - Displays the contents of the currently running configuration file or the configuration for a specific interface, or map class information.
The Lab Activities on this page will teach students how to view router configurations with the show commands. The next page will explain how a serial interface is configured.
3.1.4 This page will introduce some show commands. Many of these commands can be used to examine the contents of files in the router and for troubleshooting. In both privileged EXEC and user EXEC modes, the command show ? provides a list of available show commands. The list is considerably longer in privileged EXEC mode than it is in user EXEC mode.
Students should learn the functions of the following commands:
• show interfaces – Displays statistics for all interfaces on a router. To view the statistics for a specific interface, enter the show interfaces command followed by the specific interface slot/port number. This is shown in the following example:
Router#show interfaces serial 0/1
• show controllers serial - Displays information that is specific to the interface hardware. This command must also include the port or slot/port number of the serial interface. For example:
Router#show controllers serial 0/1
• show clock - Shows the time set in the router
• show hosts - Displays a cached list of host names and addresses
• show users - Displays all users who are connected to the router
• show history - Displays a history of commands that have been entered
• show flash - Displays information about flash memory and what IOS files are stored there
• show version - Displays information about the currently loaded software version along with hardware and device information.
• show arp - Displays the ARP table of the router
• show protocols - Displays the global and interface-specific status of any configured Layer 3 protocols
• show startup-config - Displays the saved configuration located in NVRAM
• show running-config - Displays the contents of the currently running configuration file or the configuration for a specific interface, or map class information.
The Lab Activities on this page will teach students how to view router configurations with the show commands. The next page will explain how a serial interface is configured.
Configuring router passwords
Configuring router passwords
3.1.3 This page will explain how router passwords are configured and why they are important.
Passwords restrict access to routers. Passwords should always be configured for virtual terminal (vty) lines and the console line. Passwords are also used to control access to privileged EXEC mode so that only authorized users may make changes to the configuration file.
The following commands are used to set an optional but recommended password on the console line:
Router(config)#line console 0
Router(config-line)#login
Router(config-line)#password
A password must be set on one or more of the vty lines for users to gain remote access to a router through Telnet. Most Cisco routers support five vty lines numbered 0 through 4. Other hardware platforms support different numbers of vty connections. The same password is generally used for all vty lines. However, a unique password can be set for one line to provide a fall-back entry to the router if the other four connections are in use. The following commands are used to set a password on vty lines:
Router(config)#line vty 0 4
Router(config-line)#login
Router(config-line)#password
The enable password and enable secret commands are used to restrict access to the privileged EXEC mode. The enable password is only used if the enable secret has not been set. The enable secret command should be used because the enable secret command is encrypted. The enable password command is not encrypted. The following commands are used to set the passwords:
Router(config)#enable password
Router(config)#enable secret
Sometimes it is undesirable for passwords to be shown in clear text in the output from the show running-config or show startup-config commands. This command is used to encrypt passwords in configuration output:
Router(config)#service password-encryption
The service password-encryption command applies a weak encryption to all unencrypted passwords. The enable secretcommand uses a strong MD5 algorithm for encryption.
The next page will examine show commands.
3.1.3 This page will explain how router passwords are configured and why they are important.
Passwords restrict access to routers. Passwords should always be configured for virtual terminal (vty) lines and the console line. Passwords are also used to control access to privileged EXEC mode so that only authorized users may make changes to the configuration file.
The following commands are used to set an optional but recommended password on the console line:
Router(config)#line console 0
Router(config-line)#login
Router(config-line)#password
A password must be set on one or more of the vty lines for users to gain remote access to a router through Telnet. Most Cisco routers support five vty lines numbered 0 through 4. Other hardware platforms support different numbers of vty connections. The same password is generally used for all vty lines. However, a unique password can be set for one line to provide a fall-back entry to the router if the other four connections are in use. The following commands are used to set a password on vty lines:
Router(config)#line vty 0 4
Router(config-line)#login
Router(config-line)#password
The enable password and enable secret commands are used to restrict access to the privileged EXEC mode. The enable password is only used if the enable secret has not been set. The enable secret command should be used because the enable secret command is encrypted. The enable password command is not encrypted. The following commands are used to set the passwords:
Router(config)#enable password
Router(config)#enable secret
Sometimes it is undesirable for passwords to be shown in clear text in the output from the show running-config or show startup-config commands. This command is used to encrypt passwords in configuration output:
Router(config)#service password-encryption
The service password-encryption command applies a weak encryption to all unencrypted passwords. The enable secret
The next page will examine show commands.
Configuring a router name
Configuring a router name
3.1.2 This page will explain how a router name is configured.
A router should be given a unique name as one of the first configuration tasks. This task is accomplished in global configuration mode with the following command:
Router(config)#hostname Tokyo
Tokyo(config)#
When the Enter key is pressed, the prompt will change from the default host name, which is Router, to the newly configured host name, which is Tokyo.
The next page will show students how to configure router passwords.
3.1.2 This page will explain how a router name is configured.
A router should be given a unique name as one of the first configuration tasks. This task is accomplished in global configuration mode with the following command:
Router(config)#hostname Tokyo
Tokyo(config)#
When the Enter key is pressed, the prompt will change from the default host name, which is Router, to the newly configured host name, which is Tokyo.
The next page will show students how to configure router passwords.
Configuring a router name
Configuring a router name
3.1.2 This page will explain how a router name is configured.
A router should be given a unique name as one of the first configuration tasks. This task is accomplished in global configuration mode with the following command:
Router(config)#hostname Tokyo
Tokyo(config)#
When the Enter key is pressed, the prompt will change from the default host name, which is Router, to the newly configured host name, which is Tokyo.
Configuring router passwords
3.1.3
3.1.2 This page will explain how a router name is configured.
A router should be given a unique name as one of the first configuration tasks. This task is accomplished in global configuration mode with the following command:
Router(config)#hostname Tokyo
Tokyo(config)#
When the Enter key is pressed, the prompt will change from the default host name, which is Router, to the newly configured host name, which is Tokyo.
Configuring router passwords
3.1.3
CLI command modes
CLI command modes
3.1.1 This page will discuss some features that are available from global configuration mode.
All CLI configuration changes to a Cisco router are made from global configuration mode, which is sometimes called global config. Global config is the primary configuration mode. Specific modes are used for various configuration changes, but these modes are all subsets of the global configuration mode.
Global configuration mode commands are used in a router to apply configuration statements that affect the system as a whole. The following command moves the router into global configuration mode and allows entry of commands from the terminal:
Note:
The prompt changes to indicate that the router is now in global configuration mode.
Router#configure terminal
Router(config)#
The prompt will change to indicate that the router is in global configuration mode. Here are a few of the modes that can be entered from global configuration mode:
• Interface mode
• Line mode
• Router mode
• Subinterface mode
• Controller mode
When these specific modes are entered, the router prompt changes to indicate the current configuration mode. Any configuration changes that are made will apply only to the interfaces or processes covered by the particular mode.
Type exit from one of the specific modes to return a router to global configuration mode. Pressing Ctrl-Z leaves the configuration modes completely and returns the router to privileged EXEC mode.
The next page will teach students how to configure a router name in global configuration mode.
3.1.1 This page will discuss some features that are available from global configuration mode.
All CLI configuration changes to a Cisco router are made from global configuration mode, which is sometimes called global config. Global config is the primary configuration mode. Specific modes are used for various configuration changes, but these modes are all subsets of the global configuration mode.
Global configuration mode commands are used in a router to apply configuration statements that affect the system as a whole. The following command moves the router into global configuration mode and allows entry of commands from the terminal:
Note:
The prompt changes to indicate that the router is now in global configuration mode.
Router#configure terminal
Router(config)#
The prompt will change to indicate that the router is in global configuration mode. Here are a few of the modes that can be entered from global configuration mode:
• Interface mode
• Line mode
• Router mode
• Subinterface mode
• Controller mode
When these specific modes are entered, the router prompt changes to indicate the current configuration mode. Any configuration changes that are made will apply only to the interfaces or processes covered by the particular mode.
Type exit from one of the specific modes to return a router to global configuration mode. Pressing Ctrl-Z leaves the configuration modes completely and returns the router to privileged EXEC mode.
The next page will teach students how to configure a router name in global configuration mode.
Module 3: Configuring a Router / Overview
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
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
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.
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.
Operation of Cisco IOS software
Operation of Cisco IOS software
2.1.5 This page will introduce the three distinct operating environments, or modes, of Cisco IOS devices:
The Cisco IOS devices have three distinct operating environments or modes:
• ROM monitor
• Boot ROM
• Cisco IOS
At startup, a Cisco router normally loads into RAM and executes one of these operating environments. A system administrator can use the configuration register setting to control the default startup mode for a router.
The ROM monitor performs the bootstrap process and provides low-level functionality and diagnostics. It is used to recover from system failures and to recover a lost password. The ROM monitor cannot be accessed through any of the network interfaces. It can only be accessed by way of a direct, physical connection through the console port.
When the router is running in boot ROM mode, only a limited subset of the Cisco IOS feature set is available. Boot ROM allows write operations to flash memory and is used primarily to replace the Cisco IOS image that is stored in flash. The Cisco IOS image can be modified in boot ROM with the copy tftp flash command. This command copies an IOS image that is stored on a TFTP server into the flash memory of a router.
The normal operation of a router requires use of the full Cisco IOS image as stored in flash. In some devices, the IOS is executed directly from flash. However, most Cisco routers require a copy of the IOS to be loaded into RAM and also executed from RAM. Some IOS images are stored in flash in a compressed format and have to be expanded when copied to RAM.
To see the IOS image and version that is running, use the show version command, which also indicates the configuration register setting. The show flash command is used to verify that the system has sufficient memory to load a new Cisco IOS image.
This page concludes the discussion about Cisco IOS. The next lesson will describe the initial startup of Cisco routers.
2.1.5 This page will introduce the three distinct operating environments, or modes, of Cisco IOS devices:
The Cisco IOS devices have three distinct operating environments or modes:
• ROM monitor
• Boot ROM
• Cisco IOS
At startup, a Cisco router normally loads into RAM and executes one of these operating environments. A system administrator can use the configuration register setting to control the default startup mode for a router.
The ROM monitor performs the bootstrap process and provides low-level functionality and diagnostics. It is used to recover from system failures and to recover a lost password. The ROM monitor cannot be accessed through any of the network interfaces. It can only be accessed by way of a direct, physical connection through the console port.
When the router is running in boot ROM mode, only a limited subset of the Cisco IOS feature set is available. Boot ROM allows write operations to flash memory and is used primarily to replace the Cisco IOS image that is stored in flash. The Cisco IOS image can be modified in boot ROM with the copy tftp flash command. This command copies an IOS image that is stored on a TFTP server into the flash memory of a router.
The normal operation of a router requires use of the full Cisco IOS image as stored in flash. In some devices, the IOS is executed directly from flash. However, most Cisco routers require a copy of the IOS to be loaded into RAM and also executed from RAM. Some IOS images are stored in flash in a compressed format and have to be expanded when copied to RAM.
To see the IOS image and version that is running, use the show version command, which also indicates the configuration register setting. The show flash command is used to verify that the system has sufficient memory to load a new Cisco IOS image.
This page concludes the discussion about Cisco IOS. The next lesson will describe the initial startup of Cisco routers.
Cisco IOS software features
Cisco IOS software features
2.1.4 This page will introduce some IOS images that are provided by Cisco for devices that span a wide range of network product platforms.
Cisco continues to develop different IOS software images to optimize the Cisco IOS software that these various platforms require. Each image represents a different feature set that serves the various device platforms, available memory resources, and customer needs.
Although there are numerous IOS images for different Cisco device models and feature sets, the basic configuration command structure is the same. The configuration and troubleshooting skills that are acquired for any device will apply to a wide range of products.
The naming convention for the different Cisco IOS releases contains three parts:
• The platform on which the image runs
• The special features supported in the image
• Where the image runs and whether it has been zipped or compressed
One of the main considerations when selecting a new IOS image is compatibility with the router flash and RAM memory. In general, the newer the release and the more features that it provides, the more flash and RAM memory it requires. Use the show version command on the Cisco device to check the current image and available flash.
The Cisco support site has tools available to help determine the amount of flash and RAM required for each image. For example, specific IOS features can be selected using the Cisco Software Advisor, which is available to registered Cisco.com users. The Cisco Software Advisor is an interactive tool that provides the most current information and allows users to select options that meet network requirements.
Before installing a new Cisco IOS software image on the router, check to see if the router meets the RAM memory and flash requirements for that image. To see the amount of RAM, issue the show version command:
…
2.1.4 This page will introduce some IOS images that are provided by Cisco for devices that span a wide range of network product platforms.
Cisco continues to develop different IOS software images to optimize the Cisco IOS software that these various platforms require. Each image represents a different feature set that serves the various device platforms, available memory resources, and customer needs.
Although there are numerous IOS images for different Cisco device models and feature sets, the basic configuration command structure is the same. The configuration and troubleshooting skills that are acquired for any device will apply to a wide range of products.
The naming convention for the different Cisco IOS releases contains three parts:
• The platform on which the image runs
• The special features supported in the image
• Where the image runs and whether it has been zipped or compressed
One of the main considerations when selecting a new IOS image is compatibility with the router flash and RAM memory. In general, the newer the release and the more features that it provides, the more flash and RAM memory it requires. Use the show version command on the Cisco device to check the current image and available flash.
The Cisco support site has tools available to help determine the amount of flash and RAM required for each image. For example, specific IOS features can be selected using the Cisco Software Advisor, which is available to registered Cisco.com users. The Cisco Software Advisor is an interactive tool that provides the most current information and allows users to select options that meet network requirements.
Before installing a new Cisco IOS software image on the router, check to see if the router meets the RAM memory and flash requirements for that image. To see the amount of RAM, issue the show version command:
…
Router user interface modes
Router user interface modes
2.1.3 This page will introduce two user interface modes that can be configured for Cisco IOS.
The Cisco CLI uses a hierarchical structure. This structure requires entry into different modes to accomplish particular tasks. For example, to configure a router interface, the user must enter interface configuration mode. All configurations that are entered in interface configuration mode apply only to that interface. Each configuration mode is indicated with a distinctive prompt and allows only commands that are appropriate for that mode.
The IOS provides a command interpreter service known as the command executive (EXEC). After each command is entered, the EXEC validates and executes the command.
As a security feature the Cisco IOS software separates the EXEC sessions into two access levels. These levels are user EXEC mode and privileged EXEC mode. The privileged EXEC mode is also known as enable mode. The following are the features of the user EXEC mode and privileged EXEC mode:
• The user EXEC mode allows only a limited number of basic monitoring commands. This is often referred to as a view only mode. The user EXEC level does not allow any commands that might change the configuration of the router. The user EXEC mode can be identified by the > prompt.
• The privileged EXEC mode provides access to all router commands. This mode can be configured to require a password. For added protection, it can also be configured to require a user ID. This allows only authorized users to access the router. Configuration and management commands require that the network administrator be at the privileged EXEC level. Global configuration mode and all other more specific configuration modes can only be reached from the privileged EXEC mode. The privileged EXEC mode can be identified by the # prompt.
To access the privileged EXEC level from the user EXEC level, enter the enable command at the > prompt. If a password is configured, the router will then ask for that password. For security reasons, a Cisco network device will not show the password that is entered. When the correct password is entered, the router prompt will change to #. This indicates that the user is at the privileged EXEC level. When a question mark, ?, is entered at the privileged EXEC level, it will reveal many more command options than available at the user EXEC level.
The next page covers some additional features of Cisco IOS.
2.1.3 This page will introduce two user interface modes that can be configured for Cisco IOS.
The Cisco CLI uses a hierarchical structure. This structure requires entry into different modes to accomplish particular tasks. For example, to configure a router interface, the user must enter interface configuration mode. All configurations that are entered in interface configuration mode apply only to that interface. Each configuration mode is indicated with a distinctive prompt and allows only commands that are appropriate for that mode.
The IOS provides a command interpreter service known as the command executive (EXEC). After each command is entered, the EXEC validates and executes the command.
As a security feature the Cisco IOS software separates the EXEC sessions into two access levels. These levels are user EXEC mode and privileged EXEC mode. The privileged EXEC mode is also known as enable mode. The following are the features of the user EXEC mode and privileged EXEC mode:
• The user EXEC mode allows only a limited number of basic monitoring commands. This is often referred to as a view only mode. The user EXEC level does not allow any commands that might change the configuration of the router. The user EXEC mode can be identified by the > prompt.
• The privileged EXEC mode provides access to all router commands. This mode can be configured to require a password. For added protection, it can also be configured to require a user ID. This allows only authorized users to access the router. Configuration and management commands require that the network administrator be at the privileged EXEC level. Global configuration mode and all other more specific configuration modes can only be reached from the privileged EXEC mode. The privileged EXEC mode can be identified by the # prompt.
To access the privileged EXEC level from the user EXEC level, enter the enable command at the > prompt. If a password is configured, the router will then ask for that password. For security reasons, a Cisco network device will not show the password that is entered. When the correct password is entered, the router prompt will change to #. This indicates that the user is at the privileged EXEC level. When a question mark, ?, is entered at the privileged EXEC level, it will reveal many more command options than available at the user EXEC level.
The next page covers some additional features of Cisco IOS.
Router user interface
Router user interface
2.1.2 This page will review the Cisco IOS. The IOS is a core technology that extends across most of the Cisco product line. Its operation details may vary on different internetworking devices.
The CLI environment can be accessed several ways. Typically, the CLI is accessed through a console session. A console uses a low speed serial connection directly from a computer or terminal to the console connection on the router. A CLI session can also be accessed remotely through a dialup connection using a modem connected to the router AUX port. Neither of these methods require that the router have any IP services configured. A third method of accessing a CLI session is to Telnet to the router. To establish a Telnet session to the router, at least one interface must be configured with an IP address, and virtual terminal sessions must be configured for login and passwords.
The next page discusses the different user modes that are available for Cisco IOS.
2.1.2 This page will review the Cisco IOS. The IOS is a core technology that extends across most of the Cisco product line. Its operation details may vary on different internetworking devices.
The CLI environment can be accessed several ways. Typically, the CLI is accessed through a console session. A console uses a low speed serial connection directly from a computer or terminal to the console connection on the router. A CLI session can also be accessed remotely through a dialup connection using a modem connected to the router AUX port. Neither of these methods require that the router have any IP services configured. A third method of accessing a CLI session is to Telnet to the router. To establish a Telnet session to the router, at least one interface must be configured with an IP address, and virtual terminal sessions must be configured for login and passwords.
The next page discusses the different user modes that are available for Cisco IOS.
Module 2: Introduction to Routers / Overview / The purpose of Cisco IOS software
Module 2: Introduction to Routers
Overview: Cisco technology is based on the Cisco IOS, which is the software that controls the routing and switching functions of network devices. A solid understanding of the IOS is essential for a network administrator. This module will introduce the main features of the IOS and will provide practice in working with the IOS. All network configuration tasks, from the most basic to the most complex, require a strong foundation in the basics of router configuration. This module will provide the tools and techniques for basic router configuration that will be used throughout this course.
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:
• Describe the purpose of the IOS
• Describe the basic operation of the IOS
• Identify various IOS features
• Identify the methods to establish a command-line interface (CLI) session with the router
• Alternate between the user executive (EXEC) and privileged EXEC modes
• Establish a HyperTerminal session on a router
• Log into a router
• Use the help feature in the command line interface
• Troubleshoot command errors
The purpose of Cisco IOS software
2.1.1 As with a computer, a router or switch cannot function without an operating system. This page will review the Cisco IOS. It is the embedded software architecture in all of the Cisco routers and is also the operating system of the Catalyst switches. Without an operating system, the hardware does not have any capabilities. The Cisco IOS provides the following network services:
• Basic routing and switching functions
• Reliable and secure access to networked resources
• Network scalability
The next page will discuss the Cisco IOS environment for a router.
Overview: Cisco technology is based on the Cisco IOS, which is the software that controls the routing and switching functions of network devices. A solid understanding of the IOS is essential for a network administrator. This module will introduce the main features of the IOS and will provide practice in working with the IOS. All network configuration tasks, from the most basic to the most complex, require a strong foundation in the basics of router configuration. This module will provide the tools and techniques for basic router configuration that will be used throughout this course.
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:
• Describe the purpose of the IOS
• Describe the basic operation of the IOS
• Identify various IOS features
• Identify the methods to establish a command-line interface (CLI) session with the router
• Alternate between the user executive (EXEC) and privileged EXEC modes
• Establish a HyperTerminal session on a router
• Log into a router
• Use the help feature in the command line interface
• Troubleshoot command errors
The purpose of Cisco IOS software
2.1.1 As with a computer, a router or switch cannot function without an operating system. This page will review the Cisco IOS. It is the embedded software architecture in all of the Cisco routers and is also the operating system of the Catalyst switches. Without an operating system, the hardware does not have any capabilities. The Cisco IOS provides the following network services:
• Basic routing and switching functions
• Reliable and secure access to networked resources
• Network scalability
The next page will discuss the Cisco IOS environment for a router.
Subscribe to:
Posts (Atom)
