https://learningnetwork.cisco.com/docs/DOC-7162

Recover Deleted IOS by mistakeVERSION 1 'Created on: Apr 1, 2010 7:38 PM by yasser ramzy - Last Modified:  Apr 1, 2010 7:39 PM by yasser ramzy 


i was playing with cisco router and i found this way to recover your deleted IOS by mistake:

lets begin with deleting your cisco os :



Router>
Router>ena
Router#sh ver
Router#delete flash:c2800nm-advipservicesk9-mz.124-15.T1.bin
Delete filename [c2800nm-advipservicesk9-mz.124-15.T1.bin]?
Delete flash:/c2800nm-advipservicesk9-mz.124-15.T1.bin? [confirm] 

ok now lets restart the router:



Router#reload
Proceed with reload? [confirm]

%SYS-5-RELOAD: Reload requested by console. Reload Reason: Reload Command.
System Bootstrap, Version 12.1(3r)T2, RELEASE SOFTWARE (fc1)
Copyright (c) 2000 by cisco Systems, Inc.
cisco 2811 (MPC860) processor (revision 0x200) with 60416K/5120K bytes of memory

Boot process failed...

The system is unable to boot automatically.  The BOOT
environment variable needs to be set to a bootable
image.
rommon 1 > 

wops iam in rommon hehehe 
ok now type this command :
tftpdnld

here is the output :



Missing or illegal ip address for variable IP_ADDRESS
Illegal IP address.

usage: tftpdnld
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)
FE_SPEED_MODE: 0=10/hdx, 1=10/fdx, 2=100/hdx, 3=100/fdx, 4=Auto(deflt) 

ok lets give a value for every  REQUIRED variables:



rommon 1 >IP_ADDRESS=10.0.0.1
rommon 2 >IP_SUBNET_MASK=255.0.0.0
rommon 3 >DEFAULT_GATEWAY=10.0.0.2
rommon 4 >TFTP_SERVER=10.0.0.2
rommon 5 >TFTP_FILE=c2800nm-advipservicesk9-mz.124-15.T1.bin 

now type again tftpdnld

your IOS copy from tftp server to your flash 
takecare flash will be reformatted before copy start working

before all that dont forget to connect pc with tftp server app ( with 10.0.0.2 ip address and 10.0.0.1 default gateway )directly to your router fastethernet useing crossover cable liek this :

Quote:
Router----CROSSOVER----TFTP Server