Before a router starts the booting process, it has to initialize its interfaces and then load the operating system and configuration file. To control this process the user has to find the type of image file and configuration file used by router.
When the router bots-up, the sequence of steps called as boot sequence occurs which helps to the hardware and load the required software. The boot sequence consists of following steps
Step 1: Power- on self-test: The router performs a POST is a series of hardware test that verify whether all components of the device are functional such as the POST. While performing this test the router also determines what hardware is present. The POST is stored in and executes from microcode in ROM.
Step 2: Load and run bootstrap code: The bootstrap code finds and loads Cisco IOS software. It is stored in ROM that is used to execute programs. The bootstrap program is responsible for finding the location of IOS software and then loading the file. By default, the IOS software is loaded from the flash memory in all Cisco routers. Once the IOS software is loaded, the bootstrap is not used until the router is reloaded.
Step 3: Load the IOS software: The configuration register and configuration file in NVRAM helps to determine the location of IOS image and helps to know the type of IOS image has to be used. Once it is found, the image is loaded into the RAM and starts the IOS running. Some of the router does not image from RAM but it executes directly from the Flash memory.
Step 4: Find the Configuration: The default is to look for a valid configuration file stored in NVRAM. It is also known as startup-fig.
Step 5: Load the configuration: If the stratup- config s in the NVRAM, is loaded and executed. If the startup-config is not found then the router will start the setup mode configuration upon boot up.
Using the setup command
If the router does not have a configuration file it will automatically enter Setup mode when you switch it on. Setup mode presents you with a prompted dialog called as the configuration dialog in which you can establish an initial configuration.
The prompts in the system configuration dialog of the startup command facilitate default answers inside the bracket [ ] following a question. Pressing Return key helps to use default. If the system has bee configured previously, then the default will be the currently configured values.
When the configuration process in the setup mode is completed, the configuration. When you enter “YES” the configuration will be executed and saved to NVRAM. If you enter “NO”, the configuration will not be saved and the process will start again
There are two options while using setup mode: Basic Management and Extended Setup. Basic Management only provides the configuration which allows to connect to the router but Extended setup provides the power to configure some global parameters in addition to this it also gives interface configuration parameters.
Setting global parameters
After checking the current interface summary, a prompt which signifies that the user has to enter global parameters for the router appears. These global parameters are nothing but the configuration values specified by the user.
The prompt appears as illustrated in the above figure...
The first global parameter which you can set is the host name. at initial configuration, the router name is displayed between the square brackets for example [Router]. The next global parameter is to set various passwords. First you have to enter enable password. When you enter the password characters for the prompt, Enter enable secret; the characters are then encrypted. This enhances the security of the password. Whenever you view the configuration file, the encrypted form of the password cannot be read.
Note: Enable secret password is secret word which is used instead of enable password when it exists. The “enable password” is used when “enable secret password” is not see.
Gathering Basic Routing Information
To get the basic information about router configuration, the user has to enter the commands at the CLI. The commands are generally the “show” commands. The show command cab be used o display configuration and parameters that is set.
For example:
Router#show clock
Typing Ctrl + Z will take back to global configuration mode. By using question mark (?) at any prompt you cab view list of all commands that are available and can be executed at that prompt.
Router(config)#?
gives all the commands which can be executed in the global configuration mode. This feature is referred as context-sensitive help. The question mark cab also be used to find commands which start with a certain letter. Like by typing c? at the prompt displays all the commands which start with the letter c.
Note: If you have typed an incorrect command, the caret symbol (^) and help response indicate the error. Notice that the caret symbol is displayed at the point in the command string where IOS detect an incorrect command, keyword. This error location allows you to find and correct syntax errors easily.
Show version command
The show version command is used to provide basic information on what type of Cisco IOS the router is using. In addition to this, it also gives information on system hardware, what software version you are using as well as the names, sources of configuration files and their boot images.
For example:
When the router bots-up, the sequence of steps called as boot sequence occurs which helps to the hardware and load the required software. The boot sequence consists of following steps
Step 1: Power- on self-test: The router performs a POST is a series of hardware test that verify whether all components of the device are functional such as the POST. While performing this test the router also determines what hardware is present. The POST is stored in and executes from microcode in ROM.
Step 2: Load and run bootstrap code: The bootstrap code finds and loads Cisco IOS software. It is stored in ROM that is used to execute programs. The bootstrap program is responsible for finding the location of IOS software and then loading the file. By default, the IOS software is loaded from the flash memory in all Cisco routers. Once the IOS software is loaded, the bootstrap is not used until the router is reloaded.
Step 3: Load the IOS software: The configuration register and configuration file in NVRAM helps to determine the location of IOS image and helps to know the type of IOS image has to be used. Once it is found, the image is loaded into the RAM and starts the IOS running. Some of the router does not image from RAM but it executes directly from the Flash memory.
Step 4: Find the Configuration: The default is to look for a valid configuration file stored in NVRAM. It is also known as startup-fig.
Step 5: Load the configuration: If the stratup- config s in the NVRAM, is loaded and executed. If the startup-config is not found then the router will start the setup mode configuration upon boot up.
Using the setup command
If the router does not have a configuration file it will automatically enter Setup mode when you switch it on. Setup mode presents you with a prompted dialog called as the configuration dialog in which you can establish an initial configuration.
The prompts in the system configuration dialog of the startup command facilitate default answers inside the bracket [ ] following a question. Pressing Return key helps to use default. If the system has bee configured previously, then the default will be the currently configured values.
When the configuration process in the setup mode is completed, the configuration. When you enter “YES” the configuration will be executed and saved to NVRAM. If you enter “NO”, the configuration will not be saved and the process will start again
 |
| Setup Configuration Dialog |
There are two options while using setup mode: Basic Management and Extended Setup. Basic Management only provides the configuration which allows to connect to the router but Extended setup provides the power to configure some global parameters in addition to this it also gives interface configuration parameters.
Setting global parameters
After checking the current interface summary, a prompt which signifies that the user has to enter global parameters for the router appears. These global parameters are nothing but the configuration values specified by the user.
The prompt appears as illustrated in the above figure...
The first global parameter which you can set is the host name. at initial configuration, the router name is displayed between the square brackets for example [Router]. The next global parameter is to set various passwords. First you have to enter enable password. When you enter the password characters for the prompt, Enter enable secret; the characters are then encrypted. This enhances the security of the password. Whenever you view the configuration file, the encrypted form of the password cannot be read.
Note: Enable secret password is secret word which is used instead of enable password when it exists. The “enable password” is used when “enable secret password” is not see.
Gathering Basic Routing Information
To get the basic information about router configuration, the user has to enter the commands at the CLI. The commands are generally the “show” commands. The show command cab be used o display configuration and parameters that is set.
For example:
Router#show clock
Typing Ctrl + Z will take back to global configuration mode. By using question mark (?) at any prompt you cab view list of all commands that are available and can be executed at that prompt.
Router(config)#?
gives all the commands which can be executed in the global configuration mode. This feature is referred as context-sensitive help. The question mark cab also be used to find commands which start with a certain letter. Like by typing c? at the prompt displays all the commands which start with the letter c.
Note: If you have typed an incorrect command, the caret symbol (^) and help response indicate the error. Notice that the caret symbol is displayed at the point in the command string where IOS detect an incorrect command, keyword. This error location allows you to find and correct syntax errors easily.
Show version command
The show version command is used to provide basic information on what type of Cisco IOS the router is using. In addition to this, it also gives information on system hardware, what software version you are using as well as the names, sources of configuration files and their boot images.
For example:
 |
| show version command |
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