CCNA Training - Recovering the IOS in ROMMON - Computers - Certification

As a CCNA / CCNP candidate you are expected to understand how to recover the IOS on a router when the router is in ROMMON modeDuring your time as a network engineer you will come across Cisco routers that will have lost their IOS (Internetwork Operating System software).

Cisco router may lose their IOS by various means. The main reasons that the Cisco router may lose it's IOS are:

1. User deletes the contents of flash and in the process also removes the IOS

2. The IOS becomes corrupt and fails to load

3. The user fails to upgrade the Cisco router and then reboots the router causing the router to boot into ROMMON

4. The user misspells the word start in the command "copy run start" causing the router to ask the user if they wish to delete the contents of flash, this last reason is all too common and causes no end of grief, we suggest that instead of using the "copy run start" command that you use the command "wri mem" which is an abbreviation of the command "write memory".

When your router boots and drops into ROMMON do not think that the IOS is missing, it could be that the router has experienced a bad boot process, at the "ROMMON>" prompt type the "reset" command, watch the router reboot and watch for any messages from the router stating that the router is unable to find a file in flash.

So, we find ourselves in with a router that has booted into ROMMON what do we do next, the following steps will assist in recovering the routers IOS

1. Type the following command into the Router:ROMMON>tftpdnld

At this point you will receive an output onto the console2. Make sure that you have a laptop connected to the router either directly or via a switch with a TFTP program open and showing an address that will be an address within the same subnet that you will assign to the router in a moment.

3. Enter an address for the routerROMMON>IP_ADDRESS=10.1.1.4

4. Enter the subnet for the routers interface ROMMON>IP_SUBNET_MASK=255.255.255.0

5. Enter a default gateway for the router, at this point it is good practice to simply type in the address of the laptop. DEFAULT_GATEWAY=10.1.1.100

6. Enter the IP address of the laptopTFTP_SERVER=10.1.1.100

7. Enter the name of the file that you are attempting to load into the router. Make sure that the TFTP application on the laptop has been "browsed" to the location where this IOS image resides.TFTP_FILE=c1841-advsecurityk9-mz.124-15.T1.bin

8. Press return, at this point the router will ask you is you wish to continue with the download type "yes", the routers Ethernet LED will now turn on and attempt to locate the TFTP server. If you are successful you will see a series of exclamation marks issue across the screen.

Once the router has downloaded the complete IOS to flash it will perform a lengthy checksum when complete will present the ROMMON> prompt to you, at this point type reset forcing the router to reboot and load the new IOS into RAM and booting correctly.

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