Introduction to the router (Part 1)

1. Cisco ios software

Same with the PC, router or switch will not work without the operating system. Without operating system, the hardware will not be useful. Cisco ios have the ability:

• Basic routing and switching functions
• Access to the network guaranteed keamannya
• Operates at the network scale

CLI can be accessed in different ways. In general, the CLI is accessed through a console terminal. Console using the low-speed serial connection that is connected directly to the router from your PC. CLI can also be accessed via remote dialup modem connection to the router via the Aux port. Third way is via telnet to the router. To access this via telnet, at least one router interface is configured for network address (IP address), and virtual terminal must be configured for a login and password.
Cisco CLI to have a hierarchy structure. This structure is useful to make the kind of command to the router. For example, to configure the router interface, the user must enter the configuration mode. All configuration is inserted into the interface apply only to earlier inetrface that are configured. Ios provide interpreter service, known as command executive (EXEC). After each command entered, EXEC akan validate and execute the command.
Cisco ios divided into two-level access, the user EXEC mode and privileged EXEC mode. Privileged EXEC mode, also known as enable mode. Below are the features from the user EXEC mode and privileged EXEC mode:

• User EXEC mode only has a limited commands. Usually includes only commands that are monitoring or view.User EXEC does not allow users to make configuration changes on the router. User EXEC mode is marked with a prompt>
• Contain privileged EXEC mode command = command for access to the router. This mode can be used to configure the password. And usually this mode is often used by administrators to the commandments of the configuration and management. Global configuration mode and other configuration mode can only be done through this mode. Privileged EXEC mode prompt marked with #

For access to the privileged level EXEC mode, which is located on the user-level EXEC user must type the command enable at the prompt>, if the password is entered correctly then the prompt will change to #. This indicates that the user is now in the privileged EXEC level. Commands entered at the time, it will show commands what may be done at that time.

Figure 1.1 Level user mode on the router

Figure 1.2 The change from user to privileged EXEC EXEC

Cisco is always to develop the software to update ios image features and the latest technology. Each image shows the features and services. Although there are many ios image, but the basic structure remains the same. Naming of the various Cisco ios release consists of 3 parts:

• Platform image where it is executed
• Features that are supported by a particular image
• Diamanapun image is always executed in the form of a file terkompresi

One of the things that can be used to select as acuhan ios image is compatibility with the flash and RAM. In general, the release of more new features and require increased RAM and flash that big. To find out the size of the flash image and use the command show version.
Before install Csco ios to the router, first check whether the flash and RAM required to install ios meet. To see the size of RAM you can use the command show version. As an example look at the bottom of this.

Router>show flash …

…

[12655376 bytes used, 4121840 available, 16777216 total] 16384K bytes of processor board System flash (Read/Write)

Cisco ios have 3 modes:

• ROM monitor
• Boot ROM
• Cisco ios

At startup, cisco call normal RAM and run a third of that mode. System administrators can use the configuration register setting to set the default startup.
ROM monitor is used to bootstrap the process and provide a low-level functions and for the purpose of diagnosis. This mode is used to restore the system failure (system failures) and restore the password. This mode can not be accessed via the network interface, and can only be accessed through the physical connection through the console port.
At the time of the router on the road ROM mode, only a few features that walk ios. Boot ROM allows the operation to flash memory storage and used to replace the Cisco ios image stored in flash. Cisco ios can be modified in the boot ROM with the command copy flash TFTP. This copy ios image on the TFTP server to router flash memory.
Normally the full Cisco router ios image stored in flash. Some devices, ios run directly from flash. However, most Cisco router require a copy ios to Ram and also run out of RAM. Some ios image stored in flash in the terkompresi and must be extract at the time copied to RAM.
To find out ios image and the version that is being used the way the command show version. Command is used to show me flash-memory verification that Cisco needed to load a new ios image.

Figure 1.3 Operating Cisco ios

Figure 1.4 Display command show flash

2. Running Router

Initialization is done with the router bootstrap loading, operating system and configuration files. If the router can not find the configuration file, it will enter setup mode. Once completed the configuration mode in the setup, the configuration file will be created and stored in NVRAM.
The goal of the startup process is run to start operating the router. The process should be through the startup process as follows:

• Verify the router hardware
• Search for and load the software cisco ios
• Search for and run the configuration file or to enter setup mode

When power is turned on the router first, make it power-on self test (POST). During this self test, make a diagnosis from the router to all ROM module hardware. Diagnosis for this mem-operating basis of the verification CPU, memory and port-port network interface. Once verification is complete, the router software to the process initialization procedure as follows:

• Generic bootstrap loader in ROM is executed. Bootstrap is simple commands to the hardware testing and initialization ios.
• Ios can be found in some places. Boot field from the configuration register determine the location that is used to load ios. If the boot filed to the flash point or a network, the command system on the boot configuration file also shows the location of the image.
• Operating system on the image loaded. Ios when loaded and in operation, the list hardaware and software components will be displayed on the console terminal screen.
• Configuration file in NVRAM is loaded to main memory and executed. Commands in the configuration file is executed to start the process of routing, pengalamatan interface and determine other characteristics.
• If the configuration file is invalid, operating system will find the configuration file on the TFTP server. If not found TFPT server, setup dialog that will be used.

Setup mode aims to allow network administrators to install a basic router configuration when the router does not have any configuration files. On this mode are marked with square brackets []. Press Enter to use the default option. Ctrl-C to end the process.
During the configuration process is completed in the setup mode, the display below will appear in the console terminal screen.

[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]:

Figure 2.1 Steps in the router initialization

Figure 2.2 Example of the display setup mode

Cisco routers use LED as a status indicator. LED indicator to show the interface of the indicator status of each interface. LED indicates flame interface is active and connected to the network, the LED does not indicate a flame interface is not active. If the interface is too busy, glowing green LED marked. Green means OK.

continued in the Introduction to the router (Part 2)