Memory Types

Cisco OS (IOS) are stored in different Types of Memory installed in Cisco Switches & Routers.

Four types of Cisco Switch/Router Memory:

1. FLASH Memory:

   • FLASH Memory is a Removable/Non-Removable chip which stores the original but Compressed Cisco IOS image.

   • Some part of FLASH memory can also be used to store the backup config files.

2. ROM (Read Only Memory):

   • Contains the POST & BOOTSTRAP program which finds the IOS image from FLASH Memory, decompresses & loads the compressed IOS from the Flash Memory to the RAM.

3. NVRAM (NonVolatile RAM):

   • Stores the Initial/Startup configuration file that is used when the Router/Switch is first powered on/Reloaded.

4. RAM/DRAM (Dynamic Random Access Memory):

   • Just like the computer's Random Access Memory (RAM) which is used to store the running configuration, Cisco's DRAM also does the same job.

Reference:

CCNA 200-301 OCG, Volume 1, Pg. 99-100 - Wendell Odom.