A.3 Memory

CISCO routers usually have three types of memory:

1. RAM: This is usually used by the operating system (the running operating system is located there). The content of RAM is erased when the router is shut down or there is a power outage. This memory type is usually labeled as system in commands.
2. FLASH: This memory type is not erased when a power outage occurs. It stores the operating system that is transferred into RAM when the router is switched on.
3. NVRAM: This is a smaller rewritable memory that is not erased when a power outage occurs. The router stores copies of the IOS configuration here.

Individual memory types act as file systems. Labeling is similar to the MS-DOS system, although the A:, B:, C: etc drives are replaced by a memory type such as, flash:, nvram:, system: etc. For example, a router’s start up configuration is stored in nvram:startup-config file. The configuration of a running system is in the system:running-config file.

In the newer IOS versions, we can...