problem trying to tftpdnld a new router ios to a corrupted router

Posted on 2004-10-27
Last Modified: 2008-02-01
I have a cisco1721 router. I somehow managed to totally corrupt the ios when loading SDM over the top of the ios. I have since purchased a new ios but cannot figure out how to download this onto the router. Since the ios is corrupted it does not have an ip address and therefore I cannot set the ipaddress variable of the router for tftpdnld command. How do I go about pushing this new ios image on CD down to my router?
Question by:jimburdon
    LVL 43

    Expert Comment

    You'll need to have a TFTP server running on a PC on your network.  You can get a free TFTP server at

    Console into the router.  It should be in rommon mode.  If not, you can press CTRL-BREAK within 60 seconds of the router booting to get into rommon mode.

    Once in rommon, you need to set the following variables:

    IP_ADDRESS—IP address for the router you are using.
    IP_SUBNET_MASK—Subnet mask for the router you are using.
    DEFAULT_GATEWAY—Default gateway for the router you are using (not required if the TFTP server is in the same subnet as the router).
    TFTP_SERVER—IP address of the server from which you want to download the image file.
    TFTP_FILE—Name of the file that you want to download.

    For example:

    rommon 1> IP_ADDRESS=
    rommon 2> IP_SUBNET_MASK=
    rommon 3> DEFAULT_GATEWAY=
    rommon 4> TFTP_SERVER=
    rommon 5> TFTP_FILE=c3620-i-mz.120-4.T

    Once you set the above variables, you can type the tftpdnld command and press "y" to proceed:

    rommon 6>tftpdnld
    Do you wish to continue? y/n: y

    Make sure you have your TFTP server running and the previous image in the root of the TFTP server's folder.

    Reload the router and it should come up with the new IOS.

    Author Comment

    Those were the instructions that I was trying to follow. However, as explained, I don't have the ip address of the router. THe router ios became corrupt, which is why I purcahsed teh new ios. However when you follow through the instructions it tells you to specicy certain variables, the first of which is the ip address of the router!!
    What to do?
    LVL 43

    Accepted Solution

    No, what you are doing is setting the IP address of the router, not specifying the existing IP address.  You are giving it an IP address when using the variables.
    LVL 5

    Expert Comment

    Without the IP address, you need physical access to the box, a rollover cable plugged into the console port, and a laptop.
    LVL 5

    Expert Comment

    Set the IP as  

    In the end it doesn't really matter, you can always change it, but to get your ports working it needs an address.

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