System Flash

The System Flash is an erasable and programmable memory used to store the router's IOS image. Although Flash memory is always limited in size, it can contain multiple versions of IOS. Therefore, you can delete, retrieve, and store new versions of IOS in the Flash memory system. To view the Flash on a Cisco router, use the show flash IOS command. Example 4-1 displays the Flash filename on a router named R1.

NOTE On a high-performance router, such as Cisco 4500 series and 7500 series routers, you can make the Flash system look like a file system and store many versions of IOS. The IOS command to partition the System Flash is partition flash number-of-partition size-of-each-partition.

Example 4-1 show flash Command

R1>show flash

System flash directory:

File Length Name/status

1 9558976 c2500-ajs40-l.12-17.bin

[9559040 bytes used, 7218176 available

16777216 total]

16384K bytes of processor board System


Example 4-1 shows that the IOS image, c2500-ajs40-l.12-17.bin, is currently stored on the router's on-board System Flash.

The Cisco 7500 series router provides the option of installing additional PCMCIA Flash memory. If this additional memory is installed, the dir slot0: IOS command displays the IOS image stored in slot0.

NOTE The IOS image's name conveys a lot of information, including the platform and feature sets.

For more information, go to and search for "software naming convention."

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