Types of memory on a Cisco device

Cisco devices usually have four types of memory that are being used for different purposes. These four types are:

  • ROM (Read-only memory) – stores a bootstrap program that is used to initialize a boot process. This is a read-only type of memory, so it can’t be altered.
  • RAM (Random Access Memory) – the running configuration and routing tables of the device are stored here. This type of memory loses its content when a device is restarted.
  • Flash memory – used to store IOS software images. Can also be used to store other files, for example backup configuration files.  Retains its content even after a device is restarted.
  • NVRAM (Nonvolatile RAM) – usually used to store a startup configuration file. This type of memory retains its content even after a device is powered down or restarted.