Internal Components of a Cisco Router

The Internal Components of a Cisco Router

1)Bootstrap --
       Stored in the microcode of the ROM.It will boot the router and then load the IOS.

2)POST(Power On Self Test)--
      Stored in the microcode of the ROM, the POST is used to check the basic functionality of the router hardware and determines which interfaces are present.

3)ROM Monitor --
     Stored in the microcode of the ROM, the ROM monitor is used manufacturing, testing and troubleshooting.

4)Mini-IOS --
     RxBOOT or boot-loader, small IOS in ROM that can be used to bring up an interface and load a Cisco IOS into flash memory.

5)RAM --
    Used to hold packet buffers, ARP cache, routing table and also the software and data structure that allow the router to function.Store  Running-Configuration. Most router expend IOS from flash into RAM at time of boot.

6)ROM --
    Used to store and maintain the routes. Hold the POST and Bootstrap program as well as mini IOS.

7)Flash Memory --
    Store the Cisco IOS by default. Flash memory is not erased when the router is reloaded. It is EEPROM created by Intel.

8)NVRAM --
    Used to hold the router and switch configuration. NVRAM is not erased when the router or switch is reloaded. And NVRAM doesn't store an IOS. The configuration register is stored in NVRAM.

9)Configuration Register --
    Used to control how the router boot up. By default value is 0x2102, which tells the router to load the IOS from Flash Memory as well as load the configuration from NVRAM.