The Internal Components of a Cisco Router
2 May 2009In order to configure and troubleshoot a Cisco internetwork, you need to know the major components of Cisco routers and understand what each one does. Table as below describes the major Cisco router components.
|
Component
|
Description
|
| Bootstrap | Stored in the microcode of the ROM, the bootstrap is used to bring a router up during initialization. It will boot the router and then load the IOS. |
| POST (power-onself-test) | Stored in the microcode of the ROM, the POST is used to check the basic functionality of the router hardware and determine which interfaces are present. |
| ROM monitor | Stored in the microcode of the ROM, the ROM monitor is used for manufacturing, testing, and troubleshooting. |
| Mini-IOS | Called the RXBOOT or bootloader by Cisco, the mini-IOS is a small IOS in ROM that can be used to bring up an interface and load a Cisco IOS into flash memory. The mini-IOS can also perform a few other maintenance operations. |
| RAM (randomaccessmemory) | Used to hold packet buffers, ARP cache, routing tables, and also the software and data structures that allow the router to function. Running-config is stored in RAM, and the IOS can also be run from RAM in some routers. |
| ROM (read-onlymemory) | Used to start and maintain the router. |
| Flash memory | Used on the router to hold the Cisco IOS. Flash memory is not erased when the router is reloaded. It is EEPROM (electronically erasable programmable read-only memory) created by Intel. |
| NVRAM (nonvolatileRAM) | Used to hold the router and switch configuration. NVRAM is not erased when the router or switch is reloaded. |
| Configurationregister | Used to control how the router boots up. This value can be seen with the show version command and typically is 0×2102, which tells the router to load the IOS from flash memory as well as telling the router to load the configuration from NVRAM. |
Hope this post can helping you for cisco router components, learn more for about the cisco router boot sequence here!
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