System configuration modified yet no config differences

[hreftools2014cisco]

This question is about a CISCO1941/K9 router, Version 15.0(1r)M15.

When I type

reload in 4

it asks me

System configuration has been modified. Save? [yes/no]:
% Please answer 'yes' or 'no'.

even though

show archive config differences system:running-config nvram:startup

gives

!Contextual Config Diffs:
!No changes were found

and

show running

gives

Current configuration : 5031 bytes
!
! No configuration change since last restart

My question is: how can I determine WHAT system configuration has been modified?

As far as I know, the only thing changed would be the terminal length which I occasionally toggle for use with session logging with Putty, i.e.

terminal length 0.

This router has been in production for months and I don't want to break anything (obviously).  I need to make one change to the access-list config and wanted to protect myself by telling it to reload in 4, and then I would most likely reload cancel in about 1 minute.  But now I am worried about this save yes/no question.

Thank you.

[Masoud Pourshabanian · Accepted solution]

Hi,

Just save both running config and startup config in text files and compare them. Have you activated any logging on router?  It might be because of that.

Just make sure your configuration register is 0x2102. You can see it by show version command

[hreftools2014cisco]

The configuration register is fine - thank you for caring enough to mention that.

Configuration register is 0x2102

I saved the output from "show running" and "show startup" and ran a comparison.  There was nothing different except the comments at the beginning listing the date/time of the last configuration change and when NVRAM config was last updated.

So - what would you do?  I would guess that answering 'no' is faster, and better because there is less risk of error when nothing is written. 

Just as a reminder, here's the yes/no question that comes up on 'reload in 4':

System configuration has been modified. Save? [yes/no]:

[johnlloyd_13]

hi,

normally you would choose NO.

if you recently made a change and issue the reload in x command, it will prevent you from locking out of the system/router.

[Masoud Pourshabanian]

Actually, I would say yes since for me the current state of router which is working properly is more important than configuration of long time ago. However, I would delay reloading for several days and monitor main features of router currently set.

Hope it helps,

Masoud

[hreftools2014cisco]

Just to follow-up: success.  Based on everything here, I decided that the save yes/no question must have come up because I toggled the terminal line length back and forth, so the configuration was "modified" but not actually different.

As an interesting side note, I am very glad that I waited to decide because when I went to paste in my actual changes (over long distance, VPN etc etc etc), Putty (or something) managed to insert some spaces into the port numbers I was trying to open.  i.e. an access-list command that was meant to end in '1234' for the port actually ended in '1   234' based on the Putty log that I saw afterwards.  After 3 pastes of access-list changes, the router freaked and rebooted itself -- fortunately to a completely valid startup configuration.

When I repeated the steps, I only pasted the first half of the line, waited to see it was okay in the terminal window, and then typed the remaining characters.  That way nothing extra was introduced and the router accepted all my changes.

In any case, THANK YOU KINDLY.

[Joseph W. Doherty · Accepted solution]

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Posting

I believe it may be possible that no effective changes were made.  For example, if you add a config statement, and then immediately remove it, I believe the router will indicate the configuration has changed, but logically it hasn't.

[hreftools2014cisco]

Makes sense. That explains it completely.