Cisco CCNA: Router Component Terms

In preparation of our CCNA exam, we want to make sure we cover the various concepts that we could see on our Cisco CCNA exam. So to assist you, below we will discuss Router Component Terminology.

Terminologies

Router Component Terms

TERM

DEFINITION

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-on

self-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 boot loader 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 (random access

memory)

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-only

memory)

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 (nonvolatile

RAM)

Used to hold the router and switch configuration. NVRAM is not erased when the router or switch is reloaded.

Configuration

register

Used to control how the router boots up. This value can be seen with the show version command and typically is

0x2102, which tells the router to load the IOS from flash memory as well as telling the router to load the

Configuration from NVRAM.