If the IOS image of your Router is corrupted for some reason, or if you want to install a newer version, you can do so easily with Rommon Mode. This mode can be expressed as a disaster recovery area.
How to Recover Cisco IOS with Rommon Mode from TFTP Server
You can also use different methods to back up or restore an iOS image. However, if the IOS software is corrupted or missing, you can turn on your device in Rommon monitor and recover the IOS software after setting up the TFTP server information.
What is Rommon Mode?
Rommon Mode or Rommon monitor is a Bootstrap program. Bootstrap starts the Router hardware and then boots the IOS software. This mode is enabled each time the router is restarted or turned off and on again.
If your router is turned on in Rommon, it means that there is a problem with the IOS software. So we need to restore your robust or new IOS software again using the CLI prompt.
On a router that normally works, users cannot see Rommon monitor. When the IOS image is distorted, the device automatically turns on this mode and can then be manually restarted by the user.
The utility that performs all these operations is called Rommon. It can be compared to the POST system of a computer running at boot.
Rommon is also known as ROM Monitor Mode, Boot Software, Boot Image, and Boot Helper.
How to Use Rommon Mode on Router
In this article, we will restore an deleted iOS software from the TFTP Server using ROM Monitor.
After opening your Packet Tracer software, create a simple network topology as follows. And add one TFTP server to the workspace.
Configure the TCP/IP settings of the TFTP Server.
In the Packet Tracer, click on TFTP Server and from the pop-up window, click on the Services tab and then on TFTP. If there are files in the server, delete them to avoid confusion.
Open the Cisco Router CLI tab and configure the GigabitEthernet 0/0 interface as follows.
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#interface gigabitethernet 0/0
R1(config-if)#ip address 192.168.10.1 255.255.255.0
%LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up
Before uploading the IOS software to the TFTP server, browse to the files on the Router with the show flash: command.
To upload IOS, follow the instructions below. Be sure to include the full name of the IOS software in the Source Filename section.
R1# copy tftp: flash
Source filename ? c1900-universalk9-mz.SPA.151-4.M4.bin
Address or name of remote host ? 192.168.10.100
Destination filename [c1900-universalk9-mz.SPA.151-4.M4.bin]?
IOS software successfully backed up to the TFTP server.
When you check the TFTP server in the Packet Tracer workspace, you can see the file you copied.
After this step, we will explore how to recover IOS through Rommon.
First, to delete the IOS software from the Router, execute the delete flash: command and type in the full name of the file, then press Enter to confirm.
After you set the Rommon settings, use the tftpdnld command to upload the backed up IOS software to the Router.
rommon 6 > tftpdnld
Invoke 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]:
Press Y (Yes) to confirm.
After successfully copying the iOS to the device, you must configure the Router to open it from Flash.
In rommon mode, execute th confreg-register 0x2102 command and then restart the device with the reset command.
rommon 2 > confreg 0x2102
rommon 3 > reset
Cisco Router restarts …
Bootstrap has successfully installed IOS!
Now, you can check the files with the show flash: command on the router.
To restore the IOS software of a Cisco Router on the network from TFTP, you can watch the video below and also subscribe to our YouTube channel to support us!
In this article, we have examined how to easily restore the IOS problems that occur in the Routers from Rommon mode. In real scenarios, you may need TFTP software, such as SolarWinds. Thanks for following us!