Thursday, 11 October 2012

Router Fundamentals


A Router is a network device that enables you the direct data traffic to an appropriate destination. Routers maintain routing tables that contain IP addresses of computers over the network. A router has different components that enable its proper functioning. The internetwork Operating System (IOS) acts as an operating system for the network de;vices. The IOS has many features that enable the user to interact with the devices.

Router Components :
The Router requires certain hardware and firmware components for proper functioning. These components enable the router to enter the boot up process, load its operation system, and configuration files.
A Routers has four different components.

·                            ROM : – The Read Only Memory (ROM ) is a non-volatile memory storage devices. ROM does not lose its contents when the Power supply is turned off. The components of ROM decide the boot process of the router.
1.                          POST
2.                          Bootstrap Program
3.                          Mini – IOS
RAM : - The function of Random Access Memory ( RAM ) in the router is similar to that of the memory in a computer. The RAM is a Volatile storage medium that loses data when the device is switched off. The router RAM consists of the active IOS image that is loaded when the router boots. The RAM temporarily stores the  active configuration files, routing table, interface input, and output buffers.
Flash : - The flash memory in a router is a non-volatile storage medium. The flash memory may contain IOS images using which the router can boot. Flash memory is slow, as compared to RAM. Therefore, if you compare the performance of both RAM and flash memory, RAM provides a higher rate of performance.
NVRAM : - Non-Volatile Random Access Memory ( NVRAM ) is a type of random access memory that stores configuration files for the router. The RAM is made non-volatile by attaching it to a constant source of power supply, such as a batter. The start up file and the configuration register for the router are present in the NVRAM. The configuration register specifies the boot up options for the router.

Router installation

Every router has a specific manual according to which you can assemble the router framework. The router ports may different as per the series of the router.
To install or set up a Router:
1.                          Mount the router framework as per the instructions in the Manuel.
2.                          Connect the cables to the appropriate ports.
3.                          Switch the power supply on.

Router Boot up Process

The router requires all the above components during its boot up. The router locates the IOS image during booting up. The IOS images can be present in the RAM, Flash Memory, or an FTP server in the network.
The router boot up process consists of five steps : -
1.                          Router performs the POST check for testing the hardware components and memory.
2.                          Bootstrap program is loaded and executed.
3.                          Bootstrap program locates the IOS image from flash, RAM, or the FTP server.
4.                          Bootstrap program loads the IOS.
5.                          IOS locates the configuration file present in the NVRAM.
6.                          IOS loads the configuration file. The router after boot displays the available interfaces, the network information and status of all the interfaces.
7.                          A message appears prompting to press the Enter key to continue.
You can press the enter key, To continue working with the router.

Initial Router Configuration

After the router boots, the router prompts for initial configuration. The router can be configured using three different way : -
·                            Using the Security Device Manager   –   Automatically starts for some routers.
·                            Using the Set up command facility  -  Enables us to configure a host name for the router, se passwords configure an interface for communication with the management network.
·                            Using the Command Line Interface  -  Enables manual  configuration of the router.

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