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Wednesday, May 18, 2005

Cisco tip: Restore an IOS image on a 2600

We recently had a classroom situation that required us to copy an IOS image to a router in rom monitor mode using TFTP. I hope you never have to do this, but if you do, it’s helpful to know how. We had copied a new IOS image onto the router which turned out to be corrupted. The old IOS image had already been erased, so the router had no IOS image available for its use. The router returned a rommon > prompt. By using the following series of commands, we were able to download a good IOS image from a TFTP server located at 10.16.0.13 and we were back up and running in about 15 minutes. This procedure uses the first LAN port (in our case ethernet 0/0) and can only be used for downloading a file. It cannot be used to upload a file from the router.

A tip: After you finish configuring the IP address and various related parameters, issue the sync command to copy the settings to NVRAM. That way, if you have to repeat the procedure, at least you won’t have to reenter all the settings.

You can see what settings are already in place by using the set command in ROM monitor mode.

Here’s a step-by-step guide to what you need to do:

rommon 10 > IP_ADDRESS=10.16.0.14
rommon 11 > IP_SUBNET_MASK=255.240.0.0
rommon 12 > DEFAULT_GATEWAY=10.16.0.1
rommon 13 > TFTP_SERVER=10.16.0.13
rommon 14 > TFTP_FILE=c2600-c-mz.123-3h.bin
rommon 15 > tftpdnld
IP_ADDRESS: 10.16.0.14
IP_SUBNET_MASK: 255.240.0.0
DEFAULT_GATEWAY: 10.16.0.1
TFTP_SERVER: 10.16.0.13
TFTP_FILE: c2600-c-mz.123-3h.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]: y

Receiving c2600-c-mz.123-3h.bin from 10.16.0.13..!!!!!!!!!!!!!!!!!!!!!!!!!!!!…File reception completed.

Copying file c2600-c-mz.123-3h.bin to flash.

Erasing flash at 0×607c0000program flash location 0×60440000

rommon 16 >reset[enter]

Want to know more about troubleshooting a Cisco router? Register for any of our upcoming Cisco router training classes. Whether you’re new to routers or have been working with them for years, our Cisco training seminars and workshops offer lots of real world hands-on experience in installing, configuring, optimizing, and troubleshooting. You can attend a public seminar or, for groups of four or more, bring us onsite to your location at the date and time of your choosing. Click here or call 206.988.5858 for details.

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