MEMORY ELEMENTS OF ROUTER

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 most routers expand the IOS

from flash into RAM upon boot.

Flash Memory Stores the IOS by default. Flash memory is not erased when the

router is reloaded. It is EEPROM(electronically erasable programmable read-only

memory) made by intel.

NVRAM(non-volatile RAM) Used to hold the router and switch configuration.

NVRAM is not erased when the router or switch is reloaded. Does not store an

IOS.

ROM(read-only memory) Used to start maintain the router. Holds the POST and mini IOS.