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Community Member

NVRAM 2KB in size

Hi all,

In 3660 router, after configuring the router while saving to NVRAM by wr mem or copy run start I am getting the message failed to save.See the below sh ver shows -2K bytes of NVRAM.

What went wrong and If the nvram faulty is it field replaceable or it is builtin memory so that we have to buy the whole router unit.

------------------ show version ------------------

Cisco IOS Software, 3600 Software (C3660-I-M), Version 12.4(2)T3, RELEASE SOFTWARE (fc4)
Technical Support:
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Wed 11-Jan-06 22:10 by ccai

ROM: System Bootstrap, Version 12.0(6r)T, RELEASE SOFTWARE (fc1)

Router uptime is 6 hours, 16 minutes
System returned to ROM by unknown reload cause - suspect boot_data[BOOT_COUNT] 0x0, BOOT_COUNT 0, BOOTDATA 19
System image file is "flash:c3660-i-mz.124-2.T3.bin"

Cisco 3660 (R527x) processor (revision 1.0) with 120832K/10240K bytes of memory.
Processor board ID JAB0436C05W
R527x CPU at 225MHz, Implementation 40, Rev 10.0, 2048KB L2 Cache

3660 Chassis type: ENTERPRISE
1 FastEthernet interface
4 Serial interfaces
1 Channelized (E1 or T1)/PRI port
DRAM configuration is 64 bits wide with parity disabled.
-2K bytes of NVRAM.
32768K bytes of processor board System flash (Read/Write)

Configuration register is 0x101 (will be 0x0 at next reload)

Hall of Fame Super Silver

Re: NVRAM 2KB in size

Hello Arumugasamy,

have you solved this strange issue?

the show ver shows a negative -2K NVRAM size that is not real.

How big was your running-configuration (copied to a txt file in your PC can tell you its size)?

NVRAM is somewhat limited I guess to 64 or 128 kB on a C3660.

if you need to use a config file that cannot fit in NVRAM you can consider compression or pulling config file from a TFTP server (older method)

To compress startup configuration files, use the service compress-config command in global configuration mode. To disable compression, use the no form of this command.

service compress-config

no service compress-config

I've found the following, but there is no mention about NVRAM it explains how to change RAM and internal flash

Hope to help


Community Member

Re: NVRAM 2KB in size

Dear Giuslar,

Thank you for your information.

The running config of the router is very small im size. The router is being used for the ISDN backup for the serial link.

Shall I go ahead with replacing that whole router itself since that NVRAM is not separatly orderable?



Hall of Fame Super Silver

Re: NVRAM 2KB in size

Hello Swami,

I may be wrong but for me this looks like a sw error because NVRAM size cannot be negative!

If possible, I would consider to reload the device (if you are in the conditions to recover from a possible missing startup config)

Hope to help


Re: NVRAM 2KB in size

Hi Swamy

Do you see any messages on the "show log" ? something like "%C3600-3-BADNV:" ? or anything else similar to this ? As Guisseppe posted, Im really not sure if this is a hardware issue, though not isolating this fact ! Is this router on support contract  - for TAC & replacement?



Community Member

Re: NVRAM 2KB in size

Hi All,

My customer has similar problems with their 3640 router...

System is instable, and reports error messages like:

-2K bytes of non-volatile configuration memory.

ERROR in NVRAM sizing. NVRAM could be bad!

Hardware indicated 131072 bytes. Software detected 0 bytes.

Using 0 bytes.

00:00:01: %C3600-3-BADNV: Detected invalid NVRAM size: -2056 bytes

00:00:01: %IFS-3-FS_CREATE_FAIL: Failed to create nvram file system, no NVRAM present"

I suppose its faulty NVRAM module, but I sugested few checks to be done before we declare hardware failiure:

  • Try to compress running confuguration
  • Delete any IOS images that are not supported by means of memory resaurces ot he router (customer has 1 IOS that requires more DRAM memory than the router really has)
  • Perform these sh commands:
  • sh process cpu

    sh process memory

    sh memory sum

    sh stacks

  • Backup stratup config to local computer
  • perform erase startup command
  • reload router
  • Track if problem reocurres

If problem still exists, modify confreg and set x2142 to override reading startup configuration from NVRAM...

I do not know if this last step is going to help, because confreg values should be stored in NVRAM intself, but it's worth trying :)...

After we go throw all suggested steps with no luck, I'm about to conclude that we have NVRAM chip hardware failiure...

I'll keep you informed.

Best regards,


Community Member

Re: NVRAM 2KB in size

HI ,

Please check the following thread might help!;jsessionid=32A0378853AE595143ED71163210E749.node0



Community Member

Re: NVRAM -2KB in size

Actually, as I can see from my and arumugasamy's logs, the cause of the problem is not large cofiguration, but system that shows negative NVRAM size !! Arumugasamy sad that he has basic configuration that certainly does not exceed NVRAM size. Of course, startpup config compression can do no harm , but unfortunately it will not solve the issue .

Bug toolkit is not helpfull this time (no documented issues)...

The main problem is - where to search for the problem cause - in IOS software, or in NVRAM hardware ?!

The fact that software is interpreting  NVRAM size wrong can easily lead you to both of the conclusions :).

So, do you agree that if non of the sugessted steps in all previous posts solves the problem, we have two options:

1. Try with IOS upgrade (if this is some non documented bug), or

2. If ugrade do not help, this is definatelly hardware failiure (faulty NVRAM chip) - we'll do RMA if customer has valid service contract.



Community Member

Re: NVRAM -2KB in size

Hi All,

We have opened and performed hardware testing 3640...

We put new NVRAM module, and we still got the same errors...

The conclusion is that NVRAM memory controller is broken, so either RMA should be performed, either whole matherboard should be changed...

I hope this will help you all !



Hall of Fame Super Silver

Re: NVRAM -2KB in size

Hello Ana,

thanks for your feedback on this quite uncommon issue it will be of help for somebody else that may face the same issue.

Best Regards


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