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Thread: CISCO Router lab issues

  1. #1
    Junior Member
    Join Date
    Mar 2005

    CISCO Router lab issues

    I am helping out with a CISCO class at my high school. We are running a lab with CISCO series 1600 and 1700 routers. Every once in a while, one of these routers will turn up without a IOS image. Do you guys think this is a "evil" kid, or just an accident. If the latter, what commands could accidently delete the IOS from flash?


  2. #2
    AO übergeek phishphreek's Avatar
    Join Date
    Jan 2002
    It is very easy to erase the IOS from flash...

    For example:
    Copying a file from a tftp server will prompt you to erase the flash.
    You have to tell it "n". If you just press "enter" then bye bye flash contents.

    Here is an example:

    router#copy tftp flash:
    Address or name of remote host [192.168.x.x]?
    Source filename [test.txt]?
    Destination filename [test.txt]?
    Accessing tftp://192.168.x.x/test.txt...
    Erase flash: before copying? [confirm]n
    Loading test.txt from 192.168.x.x(via Ethernet0): !
    [OK - 4 bytes]

    Verifying checksum... OK (0x1826)
    4 bytes copied in 0.048 secs (83 bytes/sec)
    Even something as simple as "erase flash:" will do it.

    router#erase flash:
    Erasing the flash filesystem will remove all files! Continue? [confirm]n
    Restoring an IOS is rather quick and easy using ROMMON and TFTP.
    Its slow and painful if you're trying to do it via xmodem or ymodem...
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  3. #3
    Right turn Clyde Nokia's Avatar
    Join Date
    Aug 2003
    Button Moon
    Yep, happens a lot on my lessons! Usually after ive been taking them through backing-up to a TFTP server! You really have to stress the "N" that goes after the erase flash before copying prompt!

    It is highly unlikley that it is a fault in the router if it only happens every now and then - but i suppose it is possible.

    AND - when I finished the practical part of a lesson I have an ACL I enable that will deny all traffic exept from my machine to the routers - you always get some smart-ass who thinks its funny to erase the flash memory or change the paswords etc which usually results in me missing my most of my lunch!
    Drugs have taught an entire generation of kids the metric system.


  4. #4
    Junior Member
    Join Date
    Mar 2005
    Thanks a lot guys! I have installed tftp servers on all of our lab stations, but knowing what can cause this problem will make things a lot easier. And thanks for the quick response!

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