Router Fundamentals
The startup routines for Cisco IOS Software have the goal of starting router operations. The router uses information from the configuration file when it starts up. The configuration file contains commands to customize router operation. As you saw in Chapter 10, "WANs and Routers," if no configuration file is available, the system configuration dialog setup guides you through creating one. The router must deliver reliable performance connecting the user networks that it was configured to serve. To do this, the startup routines must do the following:
· Make sure that the router comes up with all its hardware tested.
· Find from memory and load the Cisco IOS Software image that the router uses for its operating system.
· Find from memory and apply the configuration statements about the router, including protocol functions and interface addresses.
The router makes sure that it comes up with tested hardware. 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 modules. These diagnostics verify the basic operation of the CPU, memory, and network interface ports. After the router verifies the hardware functions, it proceeds with software initialization. You configure Cisco routers from the user interface that runs on the router console or terminal. You also can configure Cisco routers by using remote access. You must log in to the router before you can enter an EXEC command. For security purposes, the router has two levels of access to commands:
· User mode—Typical tasks include those that check the router status. In this mode, router configuration changes are not allowed.
· Privileged mode—Typical tasks include those that change the router configuration.
Concept Questions
Demonstrate your knowledge of these concepts by answering the following questions in the space provided.
1. Configuration files can come from the console, NVRAM, or a TFTP server. What are the different router modes?
· Privileged mode is used for copying and managing entire configuration files.
· Global configuration mode is used for one-line commands and commands that change the entire router.
· Other configuration modes are used for multiple command lines and detailed configurations.
2. What does it mean to configure a router?
Router configuration information can be generated by several means. You can use the privileged EXEC configure command to configure from a virtual (remote) terminal, a modem connection, or a console terminal. This enables you to enter changes to an existing configuration at any time.
You can also use the privileged EXEC configure command to load a configuration from a network TFTP server, which enables you to maintain and store configuration information at a central site.
3. Why must routers be configured?
A router must know which interfaces are to be used, which routed and routing protocols are supported, along with security and access list configurations.
4. The router initializes by loading a bootstrap, the operating system, and a configuration file. What does each of these items do?
A bootstrap is a simple, preset operation to load instructions that, in turn, cause other instructions to be loaded into memory or that affect entry into other configuration modes.
The operating system (Cisco IOS) can be found in one of several places. The location is disclosed in the boot field of the configuration register. If the boot field indicates a Flash, or network load, boot system commands in the configuration file indicate the exact location of the image.
The configuration file saved in NVRAM is loaded into main memory and is executed one line at a time. These configuration commands start routing processes, supply addresses for interfaces, set media characteristics, and so on.
5. If the router cannot find a configuration file, the router enters setup mode. What does the setup mode do?
If no valid configuration file exists in NVRAM, the operating system executes a question-driven initial configuration routine referred to as the system configuration dialog, or setup dialog.
Setup is not intended as the mode for configuring complex protocol features in the router. You should use setup to bring up a minimal configuration, and then use various configuration-mode commands rather than setup for most router configuration tasks.
6. The router stores a backup copy of the new configuration from setup mode. Where does the router store this backup copy?
The router stores in NVRAM a backup copy of the current configuration.
7. Prepare a flowchart of the startup (boot) sequence of a multimedia PC.
Refer to the Companion Guide.
8. You can use the router to do the following: log in with the user password, enter privileged mode with the enable password, disable, or quit. What procedures would you follow to log in to the router?
When you first log in to a router, you see a user-mode prompt:
Router>
At the > prompt, type enable
At the password prompt, enter the password that has been set with the enable secret command.
When you have completed the login steps, the prompt changes to a pound sign (#) because you are now in privileged mode. From privileged mode, you can access modes such as global configuration mode and other specific configuration modes.
Logging in to and out of the Router
Router con0 is now available.
Press RETURN to get started.
User Access Verification
Password:
Router>
Router> enable
Password:
Router#
Router# disable
9. You can use the following advanced help features: Command completion, command prompting, and syntax checking. Why would you need to use syntax checking?
You can use the following advanced editing features:
Þ Automatic line scrolling
Þ Cursor controls
Þ History buffer with command recall
Þ Copy and paste, which are available on most laptop computers
10. Why is it important to have two different levels of command access?
Commands available at user level are a subset of the commands available at the privileged level. For the most part, these commands enable you to display information without changing router configuration settings. You may want to have multiple administrators with varied levels of access. To access the full set of commands, you must first enable privileged mode.
Vocabulary Exercise
Define the following terms as completely as you can. Refer to the online curriculum or Chapter 11 from the Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Third Edition, for help.
Configure terminal—Command used to configure manually from the console terminal.
CPU (central processing unit)—The part of a computer that controls all the other parts. It fetches instructions from memory and decodes them. This may cause it to transfer data to or from memory or to activate peripherals to perform input or output.
erase startup-config—Command used to delete the backup configuration file in NVRAM.
Privileged mode—Typical tasks include those that change the router configuration.
Reload—The event of a Cisco router rebooting, or the command that causes the router to reboot.
User mode—Typical tasks include those that check the router status. In this mode, router configuration changes are not allowed.
The startup routines for Cisco IOS Software have the goal of starting router operations. The router uses information from the configuration file when it starts up. The configuration file contains commands to customize router operation. As you saw in Chapter 10, "WANs and Routers," if no configuration file is available, the system configuration dialog setup guides you through creating one. The router must deliver reliable performance connecting the user networks that it was configured to serve. To do this, the startup routines must do the following:
· Make sure that the router comes up with all its hardware tested.
· Find from memory and load the Cisco IOS Software image that the router uses for its operating system.
· Find from memory and apply the configuration statements about the router, including protocol functions and interface addresses.
The router makes sure that it comes up with tested hardware. 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 modules. These diagnostics verify the basic operation of the CPU, memory, and network interface ports. After the router verifies the hardware functions, it proceeds with software initialization. You configure Cisco routers from the user interface that runs on the router console or terminal. You also can configure Cisco routers by using remote access. You must log in to the router before you can enter an EXEC command. For security purposes, the router has two levels of access to commands:
· User mode—Typical tasks include those that check the router status. In this mode, router configuration changes are not allowed.
· Privileged mode—Typical tasks include those that change the router configuration.
Concept Questions
Demonstrate your knowledge of these concepts by answering the following questions in the space provided.
1. Configuration files can come from the console, NVRAM, or a TFTP server. What are the different router modes?
· Privileged mode is used for copying and managing entire configuration files.
· Global configuration mode is used for one-line commands and commands that change the entire router.
· Other configuration modes are used for multiple command lines and detailed configurations.
2. What does it mean to configure a router?
Router configuration information can be generated by several means. You can use the privileged EXEC configure command to configure from a virtual (remote) terminal, a modem connection, or a console terminal. This enables you to enter changes to an existing configuration at any time.
You can also use the privileged EXEC configure command to load a configuration from a network TFTP server, which enables you to maintain and store configuration information at a central site.
3. Why must routers be configured?
A router must know which interfaces are to be used, which routed and routing protocols are supported, along with security and access list configurations.
4. The router initializes by loading a bootstrap, the operating system, and a configuration file. What does each of these items do?
A bootstrap is a simple, preset operation to load instructions that, in turn, cause other instructions to be loaded into memory or that affect entry into other configuration modes.
The operating system (Cisco IOS) can be found in one of several places. The location is disclosed in the boot field of the configuration register. If the boot field indicates a Flash, or network load, boot system commands in the configuration file indicate the exact location of the image.
The configuration file saved in NVRAM is loaded into main memory and is executed one line at a time. These configuration commands start routing processes, supply addresses for interfaces, set media characteristics, and so on.
5. If the router cannot find a configuration file, the router enters setup mode. What does the setup mode do?
If no valid configuration file exists in NVRAM, the operating system executes a question-driven initial configuration routine referred to as the system configuration dialog, or setup dialog.
Setup is not intended as the mode for configuring complex protocol features in the router. You should use setup to bring up a minimal configuration, and then use various configuration-mode commands rather than setup for most router configuration tasks.
6. The router stores a backup copy of the new configuration from setup mode. Where does the router store this backup copy?
The router stores in NVRAM a backup copy of the current configuration.
7. Prepare a flowchart of the startup (boot) sequence of a multimedia PC.
Refer to the Companion Guide.
8. You can use the router to do the following: log in with the user password, enter privileged mode with the enable password, disable, or quit. What procedures would you follow to log in to the router?
When you first log in to a router, you see a user-mode prompt:
Router>
At the > prompt, type enable
At the password prompt, enter the password that has been set with the enable secret command.
When you have completed the login steps, the prompt changes to a pound sign (#) because you are now in privileged mode. From privileged mode, you can access modes such as global configuration mode and other specific configuration modes.
Logging in to and out of the Router
Router con0 is now available.
Press RETURN to get started.
User Access Verification
Password:
Router>
Router> enable
Password:
Router#
Router# disable
9. You can use the following advanced help features: Command completion, command prompting, and syntax checking. Why would you need to use syntax checking?
You can use the following advanced editing features:
Þ Automatic line scrolling
Þ Cursor controls
Þ History buffer with command recall
Þ Copy and paste, which are available on most laptop computers
10. Why is it important to have two different levels of command access?
Commands available at user level are a subset of the commands available at the privileged level. For the most part, these commands enable you to display information without changing router configuration settings. You may want to have multiple administrators with varied levels of access. To access the full set of commands, you must first enable privileged mode.
Vocabulary Exercise
Define the following terms as completely as you can. Refer to the online curriculum or Chapter 11 from the Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Third Edition, for help.
Configure terminal—Command used to configure manually from the console terminal.
CPU (central processing unit)—The part of a computer that controls all the other parts. It fetches instructions from memory and decodes them. This may cause it to transfer data to or from memory or to activate peripherals to perform input or output.
erase startup-config—Command used to delete the backup configuration file in NVRAM.
Privileged mode—Typical tasks include those that change the router configuration.
Reload—The event of a Cisco router rebooting, or the command that causes the router to reboot.
User mode—Typical tasks include those that check the router status. In this mode, router configuration changes are not allowed.
thank you.
ReplyDeletei think these types of information are very important now a days.As we are moving now corporate world and our dependencies on computer is been increased rapidly.and by giving this knowledge it is very helpful i can say.
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