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Upgrading a Cisco IOS Software Image into Flash Memory

Cisco routers do not usually have a disk drive. Instead, they use other types of memory for different purposes, as shown in Figure 20-1.


Figure 20-1. Types of Router Memory and Their Different Purposes

Routers usually store IOS images in flash memory.


Cover of Cisco CCNA Routing and Switching ICND2 200-101 Official Cert Guide


Note the types of memory:

Flash and RAM are both valid types of memory, but they serve different purposes. Flash stores the compressed IOS software image while RAM stores the working memory (the image decompressed for runtime usage) and the running-config.