Minimum Flash requirement for IOS image

Discussion in 'Cisco' started by realdreams, May 18, 2010.

  1. realdreams

    realdreams Guest

    image:
    IP
    c3620-i-mz.123-26.bin
    Release Date: 18/Mar/2008
    Size: 8031.25 KB (8223996 bytes)
    Minimum Memory: DRAM:48 MB Flash:32 MB

    This image is only 8MB,why it requires 32MB Flash since basically
    Flash is used to store IOS image?
    Is it true that generally I can copy an image to a Flash a little bit
    larger than the image?As long as I can copy it to flash,I can run
    it,right?

    In flash requirement,I never see sizes like 24MB.Is it because the
    Flash requirement only has 8,16,32 and so on and those irregular sizes
    are not considered but I can still run a image smaller than my
    Flash.For example,run this image with 8MB+4MB SIMM Flash.

    Thanks.
     
    realdreams, May 18, 2010
    #1
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  2. realdreams

    bod43 Guest

    Yes.

    In my experience if the image will fit the flash it will boot,
    always.

    Some platforms use flash for config storage and there is a
    small formatting overhead so you need to check the actual
    free space with sh flash.

    8223996 is awfully close to 8M and so it may well not fit
    into 8M or it might:) Also depends on whether
    1M is 1,000 x 1,000 or 1,000 * 1,024 or 1,024 x 1,024:-(

    If you want to use the on board web interface thingy
    then you need more flash. The stated flash requirements
    for modern routers includes the web thing (ah yes SDM -
    I finally recalled).
     
    bod43, May 18, 2010
    #2
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  3. realdreams

    bod43 Guest

    Also worth remembering that you can do a network boot.
    Not exactly a good idea for production but for a lab
    it would be worth considering.
     
    bod43, May 18, 2010
    #3
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