When a Cisco device fails to boot because a missing or broken image you can follow the steps below to recover the device.
For this you will need:
– A serial connection with the device
– A static IP address
– A subnet mask
– A default gateway (does not has to be a working one if the tftp server is on the same subnet. It just has to be filled in.)
– A TFTP server (like tftpd64)
– A working Cisco image file for the device
Warning!
When using this method to recover the device all files on the flash system will be deleted.
Configs and other files on the nvram are untouched.
In the example below we are going to download the c880data-universalk9-mz.154-3.M4.bin file on a Cisco C881-K9 router.
First boot the device while spamming a break (alt+b (bit like going in the BIOS of a PC). This will bring you to the rommon mode.
rommon 1 > IP_ADDRESS=10.111.111.2
rommon 2 > IP_SUBNET_MASK=255.255.255.0
rommon 3 > DEFAULT_GATEWAY=10.111.111.1
rommon 4 > TFTP_SERVER=10.111.111.1
rommon 5 > TFTP_FILE=c880data-universalk9-mz.154-3.M4.bin
rommon 6 > tftpdnld
IP_ADDRESS: 10.111.111.2
IP_SUBNET_MASK: 255.255.255.0
DEFAULT_GATEWAY: 10.111.111.1
TFTP_SERVER: 10.111.111.1
TFTP_FILE: c880data-universalk9-mz.154-3.M4.bin
TFTP_MACADDR: xx:xx:xx:xx:xx:xx
TFTP_VERBOSE: Progress
TFTP_RETRY_COUNT: 18
TFTP_TIMEOUT: 7200
TFTP_CHECKSUM: Yes
FE_PORT: 0
nvoke this command for disaster recovery only.
WARNING: all existing data in all partitions on flash will be lost!
Do you wish to continue? y/n: [n]: y
Receiving c880data-universalk9-mz.154-3.M4.bin from 10.111.111.1 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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File reception completed.
Validating checksum.
Copying file c880data-universalk9-mz.154-3.M4.bin to flash:.
Format: All system sectors written. OK…
Format: Total sectors in formatted partition: 250848
Format: Total bytes in formatted partition: %llu
Format: Operation completed successfully.
rommon 7 > boot