Q: How do I break the boot sequence on a Catalyst 3850

[lyle.cameron]

Should be a pretty simple question, but I can't seem to find an answer and I've tried all of the old tricks.

What I want to know is simple, using a terminal emulator (or in my case a Cisco router as a terminal server) how can I issue a 'break' to interrupt the boot process of a Cat 3850?

I know that if I have physical access to the switch, you just hold the 'mode' button down until the boot process is interrupted, but what if you don't have physical access?

I've changed the ENABLE_BREAK variable to 1 (using the boot enable-break switch 1 command in IOSXE), but I still can't seem to interrupt the boot process without physical access.

Is there something obvious I'm missing here?

[Richard Primm]

If I dont have access to the mode button on front, I prefer to just change the "manual boot" variable to yes. Dont forget to change it back once you are done

::Example

Switch#show boot system switch 1

---------------------------

Switch 1

---------------------------

Current Boot Variables:

BOOT variable does not exist

Boot Variables on next reload:

BOOT variable = flash:packages.conf;

Manual Boot = no  <------- Default

Enable Break = no

Switch#config t

Enter configuration commands, one per line.  End with CNTL/Z.

Switch(config)#boot manual switch 1

Switch(config)#exit

Switch#show boot system switch 1

---------------------------

Switch 1

---------------------------

Current Boot Variables:

BOOT variable does not exist

Boot Variables on next reload:

BOOT variable = flash:packages.conf;

Manual Boot = yes <--------------- now will pause on boot

Enable Break = no

++++ Dont forget to turn it off

Switch(config)#no boot manual switch 1

[lyle.cameron]

Thanks for the answer. Will definitely keep that one in mind for the future, but it doesn't help me when I can't log into a switch because of eg. mis-configured aaa config.

Cisco has seen fit to add an ENABLE_BREAK option, but I can't find how to actually send a 'break' command to the switch during bootup.

[Rasika Nayanajith]

See whether these helps

http://www.cisco.com/en/US/docs/switches/lan/catalyst3850/hardware/quick/guide/cat3850_gsg.html#wp46478

http://www.cisco.com/en/US/docs/switches/lan/catalyst3850/software/release/3.2_0_se/system_management/configuration_guide/b_sm_32se_3850_cg_chapter_010001.html#concept_6E610BCFF5174E498454F09CB6489799

Rasika

[omejia]

You can try these steps:

1. Console into the switch
2. Power cycle the switch
3. Press and hold the Mode button until it glows amber
4. When in the Switch: prompt (boot loader)
Create a new boot variable:
Switch: SWITCH_IGNORE_STARTUP_CFG=1
Verify the disable password recovery variable is not set to 1

[Aref Alsouqi]

Hi Iyle,

What emulator software are you using to access your terminal server?, also, please try to issue the command "boot enable-break" in global config mode and try again.

Here are listed some combination to send a break from different emulators:

http://www.cisco.com/c/en/us/support/docs/routers/10000-series-routers/12818-61.html

Regards,

Aref

[sbhadrav@cisco.com]

Console to the switch.  Turn off the switch and hold the mode key button in front of the switch and turn the switch on.
http://www.cisco.com/en/US/products/hw/switches/ps628/products_password_recovery09186a0080094184.shtml.

Must hold the mode switch until Syst led turns solid green at which point the switch will be at the "switch:" prompt or rmon mode.

[MichaelCole77757]

I realise this is an old post but it's still very, VERY relevant. I upgraded a pair of Cat 3650s in our data center which is a two hour drive away. The upgrade (IOS XE 16.9 - my manager likes Cisco recommendatoned) kernel panicked and rebooted, over and over until I made the frantic drive, consoled in and hit the mode button.

You know what would be really nice? An ability to do the failed upgrade, the remote terminal access and the send break boot and go direct to ROMMON without driving for hours and hours. (I can do the upgrade & the terminal access, what I cannot do is send a break.) Cisco please, give us a way to do that via terminal session.