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New Member

Config register changed to 0x0 on two 6506

Over the weekend our AC system failed in our datacentre.  Temperatures were very high.  Our tech crew was called in and restored the AC and the room cooled down.  All our equipment was ok (phew) except for our two main Catalyst 6506 switches which are setup with HSRP.  I came in and found that both switches had their config registers changed to 0x0 so they were loading into rommon.  I changed the registers and reloaded them and they both worked fine (double phew!).  My question however is why did both get their registers changed?  Is this a safety feature of some sort?  Does anyone know or has anyone seen something similar?

Everyone's tags (2)
Hall of Fame Super Gold

Maybe the line cards came

Maybe the line cards came from RMA and someone forgot to change the config-register.  

Cisco Employee

This is not expected

This is not expected behavioral.

Config register values would not get changes automatically. I am suspecting that the Conf-reg value has never been changed on this box. (To prove that if you can share the show tech or show version outputs if you have backup I can show u the same or you can view the same.)

It may also happen that you might have received the Sup modules and replaced it sometime but forgot to change the default values on it.




New Member

Thanks for the response.  I

Thanks for the response.  I can tell you that these boxes have been running for the past three years with no additional hardware added or removed.  If the confreg value was always 0x0 and hadn't been changed, how were the switches loading their ios and config files in the first place?  They've been restarted before and have always started normally.  The conf reg changed on both boxes specifically after the event I described.


Below you can see my show version output.  I'm not quite sure what you want to see in it, please let me know.


Cisco IOS Software, s3223_rp Software (s3223_rp-ADVIPSERVICESK9_WAN-M), Version 12.2(33)SXJ1, RELEASE SOFTWARE (fc2)
Technical Support:
Copyright (c) 1986-2011 by Cisco Systems, Inc.
Compiled Wed 22-Jun-11 17:11 by prod_rel_team

ROM: System Bootstrap, Version 12.2(17r)SX3, RELEASE SOFTWARE (fc1)

 CORE_6506_A uptime is 3 days, 22 hours, 51 minutes
Uptime for this control processor is 3 days, 22 hours, 51 minutes
Time since CORE_6506_A switched to active is 3 days, 22 hours, 50 minutes
System returned to ROM by power on (SP by reload)
System restarted at 12:43:46 EET2DST Mon Sep 8 2014
System image file is "sup-bootdisk:s3223-advipservicesk9_wan-mz.122-33.SXJ1.bin"
Last reload reason: Reload Command


This product contains cryptographic features and is subject to United
States and local country laws governing import, export, transfer and
use. Delivery of Cisco cryptographic products does not imply
third-party authority to import, export, distribute or use encryption.
Importers, exporters, distributors and users are responsible for
compliance with U.S. and local country laws. By using this product you
agree to comply with applicable laws and regulations. If you are unable
to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

If you require further assistance please contact us by sending email to

cisco WS-C6506-E (R7000) processor (revision 1.2) with 458752K/65536K bytes of memory.
Processor board ID SAL16138ELZ
R7000 CPU at 300Mhz, Implementation 0x27, Rev 3.3, 256KB L2, 1024KB L3 Cache
Last reset from power-on
28 Virtual Ethernet interfaces
17 Gigabit Ethernet interfaces
2 Ten Gigabit Ethernet interfaces
1915K bytes of non-volatile configuration memory.

65536K bytes of Flash internal SIMM (Sector size 512K).
Configuration register is 0x2102

Cisco Employee

Could you please share te

Could you please share te show tech when it was working fine if you have?

New Member

Hello.  Unfortunately I don't

Hello.  Unfortunately I don't have a show tech from when the system was working before the incident or a show version for that matter.  Is there any other way to find out what happened?



Cisco Employee

0x0)At the next power cycle


At the next power cycle or reload, the router boots to the ROM monitor (bootstrap program). To use the ROM monitor, you must use a terminal or PC that is connected to the router console port. For information about connecting the router to a PC or terminal, see the hardware installation guide for your router.

In ROM monitor mode, you must manually boot the system image or any other image by using the boot ROM monitor command. See the section "Booting an Image (boot)" in "Using the ROM Monitor."