From: Jay Hennigan (jay@west.net)
Date: Sun May 11 2003 - 23:36:42 GMT-3
On Sun, 11 May 2003, ccie2be wrote:
> Between you and Kym Blair, my heretofore nebulus understanding of this topic
> is becoming much clearer. You guys are great and there's hardly a day that
> goes by where I don't pick up some valuable nugget of knowledge because of
> Group Study and the generous contribution of people like yourself, Kym,
> Brian Dennis, Scott Morris ( he's an expert on Mobile IP) and many, many
> others.
>
> I think I understand what you explained to me but let me restate it in
> simple terms just to be 100% sure I got it.
>
> Some 2500 routers have code Cisco's calls, Flash Load Helper. So, those
> routers with that code don't require the register to be manually reset
> because that code causes the router to reboot into the mini ios boot mode
> automatically when the copy tftp flash command is entered. Then, after the
> router reboots, it does the copy operation, reboots again and everything is
> back to normal, except the router now has a new copy of ios.
Correct. If you're on console, you'll see the whole process. If you're
remote (dangerous if you're far remote), you'll lose the telnet session
and then (if all goes well) be able to reconnect after the upgrade.
> Other 2500 routers, don't have this code. For these routers, one has to
> manually reset the registry appropriately to have the router boot to the
> mini ios in the boot rom where once in this mode, the flash is made
> (read/write) and you can now run the copy tftp flash command. And, once the
> copy is complete reset the registry to it's normal value of 2102.
>
> If this is correct, then the logical next question is, How does one know in
> advance if the registry has to be manually reset?
Try upgrading without it.
> Apparently, having newer ios versions isn't a sure fire way to know. The
> router that wouldn't upgrade yesterday without the manual setting of the
> register was running version 12.0 something, and yet I upgraded routers
> running earlier ios versions such as 11.0, 11.1 and 11.2 without touching
> the register. I sure did get spoiled. Obviously, it's clear that if
> everthing else is OK and the copy tftp flash doesn't work, then one knows
> that the register has to be reset before proceeding, but it wouldn't
> surprise me if there's a better, less time consuming way to know which
> method needs to be used. And, assuming there is, I'm hoping you'll let me
> know.
I don't know myself specifically where all of the elements are, but would
suspect that it's a combination of new enough IOS and new enough boot ROMs.
As you start out running the full from-flash IOS, that image has to be
capable of entering flash-load-helper mode. It would have to retain in a
specific place in RAM the address of the TFTP server, the IOS filename,
and a flag to tell the boot ROM to complete the process.
Once the router has rebooted into boot ROM mode, the boot ROM mini-IOS
needs to be able to interpret the flag set by the main IOS, retrieve the
filename and TFTP IP address, complete the erase and rewrite, and reboot
to normal running configuration.
If either of these pieces aren't there, then that router won't be able
to use flash-load-helper. Caveat: This is my speculation and not from
a Cisco-verified source. It just makes sense to me. There may be something
on the CD in release notes that gives a definitive answer.
-- Jay Hennigan - CCIE #7880 - Network Administration - jay@west.net NetLojix Communications, Inc. - http://www.netlojix.com/ WestNet: Connecting you to the planet. 805 884-6323
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