Loading the IOS onto a Cisco Router
First, you must have a tftp server. All UNIX machines
come with one but you will
probabably have to enable it. I use Sun/Solaris
so these examples use Solaris.
Make sure that you have enough flash memory to load
the new image. I had to upgrade
my flash for the new 12.0(7)T image since it has now
exceded 4M.
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In the /etc/inet/inetd.conf file, uncomment the
line:
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tftp dgram udp wait root
/usr/sbin/in.tftpd in.tftpd -s /tftpboot
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This means that your upload/download directory will be
/tftpboot.
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Put the new IOS image in this directory.
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Connect to your router, either via serial console or telnet.
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You do NOT need to change the configuration register.
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enter "enable" mode.
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enter "copy tftp flash" The router will then
prompt you for the IP address of the tftp server and the name of the IOS
image.
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enter "write mem"
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That's it!
Replacing/Upgrading the flash memory.
WARNING about memory upgrades:
Make sure that you get
memory that has been made for a Cisco router. Routers run very hot
and require hi temp memory. Some routers use PC type memory (like
72 pin DIMMs) but you probably shouldn't use anything that you bought at
the local computer store unless your are sure that it won't melt!
SMART Modular Technologies and Kingston make good memory
that is significating cheaper than "real" Cisco memory (Actually, Cisco
uses SMART memory!)
This is alittle harder than a simple IOS upgrade since
there will be no IOS and you will have to use
the ROM bootstrapper.
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Make a copy of your running-config (tftp it to the tftp
server).
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Replace the flash memory DIMM.
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Connect a serial cable to the console port.
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Turn on the power to the router.
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The router will issue serveral errors relating to the
fact that there is no IOS. Don't worry about the "can't find flash"
errrors (it's not formated yet).
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You will finally get a "rommon 1>" prompt.
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enter the "tftpdnld" command. It will tell you the
parameters that must be set (tftp server IP, image name, etc).
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Parameters are set as NAME=VALUE, i.e. "TFTP_SERVER=10.0.0.1"
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VERY IMPORTANT! Set the checksum check OFF!
Otherwise, the image will be deleted after the upload because it can't
calculate the check sum (since the IOS doesn't exist yet!)
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After the IOS uploads, tftp your config back onto the
router.
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enter "write mem"
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enter "reload" (re-boot)
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That's it!
Copyright © 1993-2001 by Robert Barnes