1. Flash memory: IOS files are stored in the Flash memory. When the switch boots, the IOS files are read from the Flash memory.
2. Network servers: External locations can hold IOS image file or configuration files. This is useful for upgrade or backup purpose. You can load files from external file systems such as network servers using TFTP, and FTP.
3. NVRAM: NVRAM contains the switch configuration files. These files are used during boot-up for proper configuration of the switch.
4. RAM: The switch configuration is stored in RAM during run-time. Any configuration commands entered are first reflected in RAM. You need to use save config startup-config running-config to save them to NVRAM.