Breaking 3750/3560 remotely (only serial and power access)

Unanswered Question
Jan 27th, 2010

Hi all,

I'm trying to set up a remote lab and I'm stuck on a very stupid problem:

I need to ensure I'll still have an access to the devices in the lab even after studends possibly set/change passwords / play with aaa, etc.

So, I need to be able to drop into rommon with just a remote power switch and a serial line. No physical access at all.

This is ok for Routers, A break tunneled through the terminal server to the serial port of the router during the bootup will do it.

It is ok too for some switches(i.e. 2960): I found the command "boot enable-break" that (surprinsingly) allows to drop into rommon from serial during bootup using a break. fine.

It seems to be ok for yet some other switches (i.e. 6500 hybrid...): removing 0x0100  from the config-register removes the "ignore-break" flag.

It is not ok with the switches I mainly deal with: 3560 and 3750:

- using "(config)# boot enable-break" will correctly set the variable ENABLE_BREAK, but the device will not be breakable (break is just ignored: furthermore, the boot enable-break which is in all documentation for these devices is also in the Unsupported commands list...).

- using "rommon> confreg 0x..." won't work as there is no such keyword available in rommon.

- using "(config)# set boot config-register 0x..." won't work, the command is not recognized by IOS.

- using "rommon> set CONFIG_REGISTER 0x... doesn't seem to have any effect. and the config-register in show ver is still 0xF

Is there a savior out there that would know an alternative ? the only solution I'm left with would be a robot moving along the rack pushing "mode" buttons while rebooting devices... I'm kind of depressed ;-)

Thanks in advance for any idea,


I have this problem too.
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bxnetworx Sun, 06/12/2016 - 01:16

Did you ever find a solution to this problem?  I'm in a similar boat.  We have 3560 switches all around our plant, many of which are only accessible via a scissor lift.  True out of band management shouldn't necessitate that one resort to desperate hacks like using solenoid actuators to push buttons.


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