ROMMON tftpdnld is my friend

After watching my router go around and around in circles, continually failing to boot, I decided enough was enough. Time to break out ROMMON tftpdnld.

I've used ROMMON before to download a TFTP image, but it's never something I remember off the top of my head. In the interests of this being my own personal wiki, and so it's here for anyone else it benefits (though it's a pretty well documented topic on Google!), here goes.

Firstly, tftpdnld will only work on the first LAN interface. (On some platforms that can be changed I believe, but I've never seen it). So make sure the cable is in the lowest number interface.

To stop the router circling, press ctrl-break. Side note here: I was using a USB-RS232 adapter. Every time I pressed Ctrl-Break I got about 3 lines of error message. Unfortunately I didn't copy them. I ended up finding an old PC with a COM port, but I've since found this tech note from Cisco

This will drop you to a ROMMON 1> prompt.

From here, the usage instructions for tftpdnld are:

usage: tftpdnld [-ur]

Use this command for disaster recovery only to recover an image via TFTP.

Monitor variables are used to set up parameters for the transfer.

(Syntax: "VARIABLE_NAME=value" and use "set" to show current variables.)

"ctrl-c" or "break" stops the transfer before flash erase begins.

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

The following variables are OPTIONAL:

TFTP_VERBOSE: Print setting. 0=quiet, 1=progress(default), 2=verbose

TFTP_RETRY_COUNT: Retry count for ARP and TFTP (default=7)

TFTP_TIMEOUT: Overall timeout of operation in seconds (default=7200)

TFTP_CHECKSUM: Perform checksum test on image, 0=no, 1=yes (default=1)

Command line options:

-r: do not write flash, load to DRAM only and launch image

-u: upgrade the rommon, system will reboot once upgrade is complete

The variables are set by typing:

IP_ADDRESS=192.168.0.1

Everything I've said here can be found at:  How to Download a Software Image to a Cisco 2600 via TFTP Using the tftpdnld ROMMON Command 

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