How to Recover Cisco Router IOS using Rommon Mode in Cisco Packet Tracer

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 Router IOS Using Rommon Mode in Cisco Packet Tracer

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.

   Step 1

After opening your Packet Tracer software, create a simple network topology as follows. And add one TFTP server to the workspace.

A Switch and TFTP Server Connected to Cisco Router

   Step 2

Configure the TCP/IP settings of the TFTP Server.

TFTP Server TCP/IP Settings

   Step 3

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.

Enabling TFTP Service

   Step 4

Open the Cisco Router CLI tab and configure the GigabitEthernet 0/0 interface as follows.

Router> en
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname R1
R1(config)#
R1(config)#interface gigabitethernet 0/0
R1(config-if)#ip address 192.168.10.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#
%LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up
R1(config-if)#exit
R1(config)#

 
Assigning an IP Address to the GigabitEthernet Interface

   Step 5

Before uploading the IOS software to the TFTP server, browse to the files on the Router with the show flash: command.

Show Flash Command

   Step 6

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]?

Writing c1900-universalk9-mz.SPA.151-4.M4.bin...

 
Copy IOS Image to TFTP

   Step 7

IOS software successfully backed up to the TFTP server.

Upload Complete

   Step 8

When you check the TFTP server in the Packet Tracer workspace, you can see the file you copied.

Checking IOS on a TFTP Server

   Step 9

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.

R1# delete flash:
Delete filename []? c1900-universalk9-mz.SPA.151-4.M4.bin
Delete flash:/c1900-universalk9-mz.SPA.151-4.M4.bin? [confirm]

 
Delete Flash Command

   Step 10

After deleting the IOS, use the config-register 0x2100 command to turn on the device in Rommon. Then restart the router with the Reload command.

R1(config)# config-register 0x2100

 
R1(config)# config-register 0x2100

   Step 11

As you can see in the image below, the Router is now in ROM Recovery.

Rommon Mode

   Step 12

You must configure the Rommon mode of the router. Set the TCP/IP information first, and then type the IP address of the TFTP server on your network.

Finally, type the full name of the file you want to copy from the TFTP server.

rommon 1 > IP_ADDRESS=192.168.10.1
rommon 2 > IP_SUBNET_MASK=255.255.255.0
rommon 3 > DEFAULT_GATEWAY=192.168.10.1
rommon 4 > TFTP_SERVER=192.168.10.100
rommon 5 > TFTP_FILE=c1900-universalk9-mz.SPA.151-4.M4.bin

 
Configuring Rommon

   Step 13

After you set the Rommon settings, use the tftpdnld command to upload the backed up IOS software to the Router.

rommon 6 > tftpdnld

IP_ADDRESS: 192.168.10.1
IP_SUBNET_MASK: 255.255.255.0
DEFAULT_GATEWAY: 192.168.10.1
TFTP_SERVER: 192.168.10.100
TFTP_FILE: c1900-universalk9-mz.SPA.151-4.M4.bin
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]:

 
tftpdnld command

   Step 14

Press Y (Yes) to confirm.

Confirming the Import of IOS

   Step 15

After successfully copying the iOS to the device, you must configure the Router to open it from Flash.

Recovering Router's Image File

   Step 16

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

 
confreg-register 0x2102

   Step 17

Cisco Router restarts …

Restarting Cisco Router

   Step 18

Bootstrap has successfully installed IOS!

Now, you can check the files with the show flash: command on the router.

c1900 IOS

   Video

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!

   Final Word


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!

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2 Comments

  1. Avatar for Alexander Alexander 15 September 2017

    Very thanks, this is the useful article.

    Reply

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