System Flash

The System Flash is 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 Cisco IOS software. Therefore, you can delete, retrieve, and store new versions of Cisco IOS software in the

Flash memory system. To view the Flash memory on a Cisco router, use the show flash IOS command. Example 3-1 displays the Flash filename on a router named R1.

NOTE On a high-performance router, such as Cisco 3800 series or 7500 series routers, you can make the Flash system look like a file system and store many versions of Cisco IOS software. The IOS command to partition the System Flash is partition flash number-of-partition size-of-each-partition. Even on a low-end router, such as the 2500, the Flash can be partitioned.

Example 3-1 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 3-1 shows that the IOS image, c2500-ajs40-l.12-17.bin, is currently stored on the router's on-board System Flash.

The Cisco IOS series routers, such as the 7500 or 3800 series, provide 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 Cisco recently renamed all of its IOS images to permit a total of only eight possible trains. Visit for more details. This link requires a Cisco CCO account.

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