From: Sam Munzani (sam@munzani.com)
Date: Mon May 12 2003 - 11:34:39 GMT-3
In 2500 series there used to be 2 different kind of routers. 2500 and
2500-R. The second kind of routers had enough RAM to run whole IOS from the
RAM. It needed flash only during boot up and after that whole image was
loaded in the RAM. These routers you can upgrade without config-register
changes. All others required config register changes.
Sam Munzani
CCIE # 6479
> Hey Kym,
>
> That has to be one of the best technical explanations I've ever seen.
It's
> certainly the only one on this topic that's ever made total sense. Thank
> you for taking the time to put in all the details. I'm sure many people
> here on group study besides myself will greatly appreciate being able to
> understand this.
>
> There is one thing, however, that I still don't understand. At least half
a
> dozen times I've upgraded the ios on 2500's without changing the register.
> I would do a copy tftp flash, then enter the source ip address, file name,
> etc. and the router would just copy the new ios into flash and then
reboot.
> When the router came back up it had the new ios. So, why does the
register
> sometimes have to be changed to upgrade the ios but not other times?
>
> This method worked on some routers even when the new ios was almost 16mb
in
> size and the old ios was erased first. Is there a way to know beforehand
> which method has to used?
>
> Thanks once again. Jim
>
> ----- Original Message -----
> From: "kym blair" <kymblair@hotmail.com>
> To: <ccie2be@nyc.rr.com>
> Sent: Saturday, May 10, 2003 9:41 PM
> Subject: Re: IOS Upgrade problem
>
>
> > Jim,
> >
> > Most cisco routers copy the IOS into DRAM and run from DRAM, so flash is
> > READ-WRITE. 2500 routers execute from flash, so flash must be
READ-ONLY.
> > When you would like to erase and upgrade the image in flash, you need to
> > boot from BOOTFLASH (an older IOS version burned into BOOTFLASH chip).
> >
> > The config-register is a 16-bit register where each bit controls some
boot
> > option. For normal operation, boot to 0x2102 (i.e., 0010 0001 0000
0010;
> > bit "15" is on the left; bit "1" is on the right).
> >
> > For maintenance, you may want to change the config-register and reload.
> >
> > FIRST DIGIT: You will probably always want to keep the first digit set
to
> > "2" so bit 13 instructs the CPU to "boot from ROM if all else fails".
> >
> > SECOND DIGIT: You will probably also want to always keep the second
digit
> > set to "1" so bit 8 instructs the CPU to "disable [BREAK] after bootup".
> >
> > THIRD DIGIT: you may want to change the third digit to "4" ... bit 6 set
> to
> > '0' says "copy startup-config into running-config during bootup", where
> bit
> > 6 set to '1' says "don't use startup-config during the next bootup". If
> you
> > set bit 6, you won't load the startup-config, but it will still be there
> in
> > NVRAM. During operation, you could still "copy startup-config
> > running-config".
> >
> > FOURTH DIGIT: Most importantly, you can instruct the router to boot
> full-up
> > using the image in flash (0x2102), or boot from older image in bootflash
> > (0x2101 or 0x2141), or boot into near-braindead ROMMON mode (0x2100).
> Here
> > are the various "show versions":
> >
> >
> > ========== 0x2102 full boot from flash =================
> >
> > R3#sh version
> > <snip>
> > System image file is "flash:c2500-js-l.122-1.bin""
> > <snip>
> > 16384K bytes of processor board System flash (Read ONLY)
> > <snip>
> > Configuration register is 0x2102
> >
> > ========== 0x2101 boot from bootflash ===================
> >
> > R3(boot)#sh version
> > <snip>
> > System image file is "bootflash:"
> > <snip>
> > 16384K bytes of processor board System flash (Read/Write)
> > <snip>
> > Configuration register is 0x2101
> >
> > ========== 0x2100 boot into ROMMON mode =================
> >
> > >sh version
> > ------ <nothing returned> -----
> > >?
> > $ Toggle cache state
> > B [filename] [TFTP Server IP address | TFTP Server Name]
> > Load and execute system image from ROM or from TFTP server
> > C [address] Continue execution [optional address]
> > D /S M L V Deposit value V of size S into location L with modifier M
> > E /S M L Examine location L with size S with modifier M
> > G [address] Begin execution
> > H Help for commands
> > I Initialize
> > K Stack trace
> > L [filename] [TFTP Server IP address | TFTP Server Name]
> > Load system image from ROM or from TFTP server, but do not
> > begin execution
> > O Show configuration register option settings
> > P Set the break point
> > S Single step next instruction
> > T function Test device (? for help)
> >
> > Deposit and Examine sizes may be B (byte), L (long) or S (short).
> > Modifiers may be R (register) or S (byte swap).
> > Register names are: D0-D7, A0-A6, SS, US, SR, and PC
> > >
> > >o
> > Configuration register = 0x2100 at last boot
> > Bit# Configuration register option settings:
> > 15 Diagnostic mode disabled
> > 14 IP broadcasts do not have network numbers
> > 13 Boot default ROM software if network boot fails
> > 12-11 Console speed is 9600 baud
> > 10 IP broadcasts with ones
> > 08 Break disabled
> > 07 OEM disabled
> > 06 Ignore configuration disabled
> > 03-00 Boot to ROM monitor
> > >
> > >o/r 0x2102 <--- sets back to 0x2102
> > >b
> >
> >
> > One last item that is probably not useful on a 2500 router ... instead
of
> > setting the last digit to "2" for full-up operation, you could set the
> last
> > digit to "3", "4", ... "F". The "2" means to run the image in flash
named
> > "cisco2-2500" or the first image found. If you reconfigured to "0x2103"
> you
> > would be instructing the router to run the image in flash named
> > "cisco3-2500" or the first image found. This allows you to store
several
> > images in flash (memory permitting), and boot whichever you need today.
> >
> > HTH, Kym
> >
> >
> >
> >
> > >From: "ccie2be" <ccie2be@nyc.rr.com>
> > >To: "Group Study" <ccielab@groupstudy.com>, "kym blair"
> > ><kymblair@hotmail.com>
> > >Subject: Re: IOS Upgrade problem
> > >Date: Sat, 10 May 2003 20:10:05 -0400
> > >
> > >Hey Kym,
> > >
> > >Thank you so much. I don't understand why these register settings
work,
> > >but
> > >so far, it's seems to be working fine. Right now the router is in the
> > >process of copying over the new ios.
> > >
> > >I looked up the register settings in Solie's Practical Studies and he
> > >doesn't mention anything about bit 6 or bit 1 changing the flash from
> read
> > >only to read/write. Instead, he says setting bit 6 to 1 (4 decimal)
> causes
> > >the rtr to ignore nvram and bit 1 means to boot to boot mode. So, if
you
> > >could explain it, I'd like to understand why this works.
> > >
> > >But, in any case, this does work and I very much appreciate you help.
> Jim
> > >
> > >----- Original Message -----
> > >From: "kym blair" <kymblair@hotmail.com>
> > >To: <ccie2be@nyc.rr.com>; <ccielab@groupstudy.com>
> > >Sent: Saturday, May 10, 2003 6:50 PM
> > >Subject: Re: IOS Upgrade problem
> > >
> > >
> > > > Jim,
> > > >
> > > > Set your config register to 0x2141 and reload. After installing
your
> > >new
> > > > IOS, change the config register back to 0x2102:
> > > >
> > > >
> > > >
> > > > R1(boot)#sh version
> > > > <snip>
> > > > 16384K bytes of processor board System flash (Read ONLY)
> > > > Configuration register is 0x2102
> > > >
> > > >
> > > > R1#conf t
> > > > R1(config)#config-reg 0x2141
> > > > R1(config)#end
> > > > R1#reload
> > > >
> > > > System configuration has been modified. Save? [yes/no]: no
> > > > Proceed with reload? [confirm]
> > > >
> > > >
> > > > Router(boot)#sh version
> > > > <snip>
> > > > 16384K bytes of processor board System flash (Read/Write)
> > > > Configuration register is 0x2141
> > > >
> > > >
> > > >
> > > > HTH, Kym
> > > >
> > > >
> > > >
> > > > >From: "ccie2be" <ccie2be@nyc.rr.com>
> > > > >Reply-To: "ccie2be" <ccie2be@nyc.rr.com>
> > > > >To: "Group Study" <ccielab@groupstudy.com>
> > > > >Subject: IOS Upgrade problem
> > > > >Date: Sat, 10 May 2003 16:01:11 -0400
> > > > >
> > > > >Hi group,
> > > > >
> > > > >I'm trying to upgrade from ios 12.0 to 12.1 on a 2501 with 16 mb
> flash.
> > > > >The
> > > > >router to be upgraded also has version 11.0 bootstrap. The flash
> isn't
> > > > >partitioned and the version of ios I'm trying to copy is running
fine
> > >on
> > > > >another 2501. I've tried copying the ios from both a PC running
> > >Cisco's
> > > > >TFTP
> > > > >server s/w as well as another 2501 configured as a TFTP server. It
> > >doesn't
> > > > >work in either case.
> > > > >
> > > > >I go through the tftp process but shortly after it starts, it
fails.
> (
> > >I
> > > > >can
> > > > >ping the tftp server just fine.)
> > > > >
> > > > >I also noticed that with sho version, it says, 16384k bytes of
> > >processor
> > > > >board
> > > > >system flash (read only)
> > > > >
> > > > >
> > > > >On some of my other 2501's, it says, (read/write) instead of (read
> > >only).
> > > > >Could this be the problem? And, how do I change the flash from
(read
> > >only)
> > > > >to
> > > > >(read/write)?
> > > > >
> > > > >Thanks in advance, Jim
> > > >
> > > > _________________________________________________________________
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