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.
Wednesday, May 12, 2010
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.
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