you can use a Compact flash of another device/Router, provided that flash card has the proper IOS for your 2921 router otherwise without CF, you would not be able to break the password
But in the worst case scenario i.e you do not have another CF and are not able to get a new one as suggested earlier and your router is not usable at all, you can try one of the following steps (whichever is supported in your platform rommon). These options require reboot and your router might be rendered useless (unless you bring in the CF with the IOS file on it) if none of them works, so do keep them as the LAST option -
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tftpdnld command
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You need to connect the TFTP server to the ethernet port of your router, tftp server
should be running and then do these steps:
Example --
rommon 2 > confreg 0x2142
rommon 3 >IP_ADDRESS=172.18.16.76 (it should be in the same subnet as the PC)
rommon 4 >IP_SUBNET_MASK=255.255.255.192
rommon 5 >DEFAULT_GATEWAY=172.18.16.76 (can be the same as router's ethernet port)
rommon 6 >TFTP_SERVER=172.18.16.2
rommon 7 >TFTP_FILE=c871-i-mz.123-83YI1.bin
The following variables are REQUIRED to be set for tftpdnld:
IP_ADDRESS: The IP address for this unit
IP_SUBNET_MASK: The subnet mask for this unit
DEFAULT_GATEWAY: The default gateway for this unit
TFTP_SERVER: The IP address of the server to fetch from
TFTP_FILE: The filename to fetch
rommon 8 >tftpdnld -r
It will download the IOS from TFTP server to DRAM
****When the router boots up, the image is just in DRAM and it has ignored FLASH. Please
make a note that do not reboot the router
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xmodem command
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Once in ROMmon, change the console baud rate from 9600 bps to 115200 bps to speed up the
download time. Use the confreg command and follow the instructions presented on the
screen.
rommon 1 >confreg
Configuration Summary
enabled are:
break/abort has effect
console baud: 9600
boot: the ROM Monitor
do you wish to change the configuration? y/n [n]: y
enable "diagnostic mode"? y/n [n]:
enable "use net in IP bcast address"? y/n [n]:
enable "load rom after netboot fails"? y/n [n]:
enable "use all zero broadcast"? y/n [n]:
disable "break/abort has effect"? y/n [n]:
enable "ignore system config info"? y/n [n]:
change console baud rate? y/n [n]: y
enter rate: 0 = 9600, 1 = 4800, 2 = 1200, 3 = 2400
4 = 19200, 5 = 38400, 6 = 57600, 7 = 115200 [0]: 7
change the boot characteristics? y/n [n]:
Configuration Summary
enabled are:
break/abort has effect
console baud: 115200
boot: the ROM Monitor
do you wish to change the configuration? y/n [n]:
3) Reset or power cycle the router for new config to take effect. And you will have to
open a new hyperterminal session and select the 115200 baud rate in the settings
4) Issue following command:
rommon1>xmodem -yr
Example:
rommon1>xmodem -yr c2600-is-mz.122-10a.bin
5) From the HyperTerminal menu bar select Transfer > Send and specify the:
*Image name/location
* Select the protocol as Y modem and start the transfer.
It should reboot itself and come to a router prompt.
****At this point the image is just in DRAM and it has ignored FLASH. Please make a note
if the router boots fine and DO NOT reboot the router
