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  1. Senior Member
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    #1

    Default "del vlan.dat" and "erase startup.config"

    Just try to wrap my mind around some basic router/switch idea. I tried the commands "erase start" and "del vlan.dat" on a switch. They seem to tell me, the file start-up.config is stored in nvram and the file vlan.dat is stored in flash.

    Since I'm familiar with PCs, I'm thinking why these files aren't kept on the same disk space?

    And why does IOS come up with two very similar commands, del and erase, for just two different file?


    -----
    S3#erase start
    Erasing the nvram filesystem will remove all configuration files! Continue? [confirm]
    [OK]
    Erase of nvram: complete
    S3#
    *Mar 1 00:02:12.427: %SYS-7-NV_BLOCK_INIT: Initialized the geometry of nvram
    S3#del vlan.dat
    Delete filename [vlan.dat]?
    Delete flash:vlan.dat? [confirm]
    S3#
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  3. Senior Member iamme4eva's Avatar
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    #2
    From my understanding, though I may be wrong:

    Delete is used to delete a specific file, where as erase is used to wipe a file system.

    "erase startup-config" and "write erase" are considered older commands, and the newer command is "erase nvram".

    When you erase the startup config, you are wiping the entire NVRAM, as it's the only thing stored there.

    I think I once read somewhere that on newer models the NVRAM has become a partition on the flash card rather than a dedicated chip.
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  4. Senior Member WilyOne's Avatar
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    #3
    Well there is no "disk space", this is all done in various forms of memory. But I understand your question since NVRAM and Flash are very similar. I think the reason why IOS stores different things in different types of memory goes back to historical reasons, back when NVRAM was new, capacities were smaller, and so forth.

    The bottom line is for the CCNA exam you need to know what is stored where.
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  5. Senior Member
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    #4
    When I was going over this concept, I couldn't find an answer. If Google doesn't have it, then it's not answerable. NVRAM is non-volitaile, meaning it doesn't lose it's contents when power is turned off. But can't the same be said for flash memory?? I don't think there is an answer.
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  6. Senior Member
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    #5
    Quote Originally Posted by pamccabe View Post
    When I was going over this concept, I couldn't find an answer. If Google doesn't have it, then it's not answerable. NVRAM is non-volitaile, meaning it doesn't lose it's contents when power is turned off. But can't the same be said for flash memory?? I don't think there is an answer.
    NVRAM is a small amount of non-volatile memory used exclusively to store the startup-config. Flash is a larger amount of non-volatile memory used to store the IOS [and in most cases the VLAN Database]. I believe at one time NVRAM was a separate chip, but is now simply a partition in Flash memory. Are they the same thing? Yes and No. They are both non-volatile memory, but they are used for different purposes and are very different in size (32K vs. 4 to 256 MB or more).

    BTW, I'd have to check, but I'm pretty sure you can't save anything [other than the startup-config] to NVRAM. It exists strictly for the startup-config. OTOH, you can write files to Flash. I sometimes save backups of my startup-config in flash before making changes.
    Last edited by theodoxa; 07-29-2013 at 12:07 AM.
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  7. Senior Member
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    #6
    yes theodoxa, you can actually setup an http server on your router and save files on your flash to act as a web server... it's not too realistic, but possible. I just think it might be out of scope for the CCNA. You are knowledgeable though, and appreciate the feedback.
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