Upload Cisco IOS from ROMmon Mode using Boot Image

What is Cisco Boot Image?:

The boot image is a subset of the Cisco IOS® software that is used to download main Cisco IOS software images to the router via TFTP in recovery situations. The user can interact with this image through a command line interface signified by the prompt Router(boot)#. This image called as xboot image, rxboot image, bootstrap image, or boot loader or helper image, which depends on your platform. The boot image has limited capabilities. For example, it does not contain routing information.

Note: Don’t save your configuration while in boot mode, as part of the configuration (such as the routing part) is lost if saved this way.

Change Configuration Register to Load the Boot Image:

If your Router contains a valid boot image, it can be used to download a valid Cisco IOS Software image into the Flash using TFTP. In order to do this, perform below steps:

1. Change the configuration register to boot the boot image by changing the configuration register as follows.

rommon 1 > confreg 0x2101 or > o/r 0x2101

2. You must reset or power cycle for the new configuration to take effect. Boot the boot image by resetting the router:

rommon 2 > reset or > i

3. The System Bootstrap message appears and the router boots its boot image. On the screen, you should see something like this:

System Bootstrap, Version 11.1(10)AA, EARLY DEPLOYMENT RELEASE      SOFTWARE (fc1)
Copyright (c) 1997 by cisco Systems, Inc.
C1600 processor with 18432 Kbytes of main memory
program load complete, entry point: 0x4018060, size: 0x1e1568
Restricted Rights Legend

You should now have a prompt similar to Router(boot)>


Upload Cisco IOS Image using Boot Image:

4. Connect the Ethernet interface 0 of your router to the network, through which you can reach the TFTP server. Configure the IP address on the Ethernet interface of the router.

Router(boot)#configure terminal
Router(boot)(config)#interface ethernet 0
Router(boot)(config-if)#ip address
Router(boot)(config-if)#no shutdown

5. Routers that run boot images do not have routing capabilities. Therefore, a default gateway for this router must be configured. This should point to the IP address of the router attached to the same subnet as your Ethernet 0 interface.

Router(boot)(config)#ip default-gateway

6. Before you copy the Cisco IOS image from the TFTP server, make sure that the router has connectivity to the TFTP server.

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echoes to, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms

7. Copy the Cisco IOS image from the TFTP server to the Flash memory on the router.

Router(boot)#copy tftp flash
PCMCIA flash directory:
No files in PCMCIA flash
[0 bytes used, 16777216 available, 16777216 total]
Address or name of remote host []?
Source file name? c1600-y-l.122-10d.bin
Destination file name [c1600-y-l.122-10d.bin]?
Accessing file ‘c1600-y-l.122-10d.bin’ on…
Loading c1600-y-l.122-10d.bin from (via Ethernet0):
! [OK]  Device needs erasure before copying new file
Erase flash device before writing? [confirm]y
Copy ‘c1600-y-l.122-10d.bin’ from server as ‘c1600-y-l.122-10d.bin’
into Flash WITH erase? [yes/no]yes
Erasing device…
eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee  …erased
Loading c1600-y-l.122-10d.bin from (via Ethernet0):
[OK – 7220632/16777216 bytes]Verifying checksum…  OK (0x6526)
Flash device copy took 00:05:57 [hh:mm:ss]

8. Change the configuration register value back to x2102 for the router to boot with the newly uploaded Cisco IOS image during the next reload.

Router(boot)#configure terminal
Router(boot)(config)#config-register 0x2102

9. Reload the router by issuing the reload command.

System configuration has been modified. Save? [yes/no]: no
Building configuration…
Proceed with reload? [confirm] -–Press Enter —

10. After booting the Router you can verify image has been loaded into the router is correct or not by using the show version command.

Router>show version

Filed Under: Cisco General


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