[mrtg] Re: Blank graphs

[Garry Cook]

This sounds similar to a problem we had last year. After upgrading from RH 7.0 to 7.1, when one of our routers would fail all of the graphs would start appearing blank. One of our admins tracked it down as a bug in the kernel and wrote the following script to flush the IP routing cache. This script was then placed in /etc/cron.hourly and the problem was 'corrected'.

##################################################################################
#!/bin/sh
#
#  There is a bug in the kernel that trips up SNMP operations when hosts are down.  Therefore,
#  we reset the IP routing cache every hour to cover up this problem until the appropriate
#  kernel fix is available.
#

ip route flush cache
##################################################################################

I don't know if this is your issue, but as I mentioned, it sounds similar.
I've since upgraded to the latest kernel and killed the script. The problem seems to have been corrected. I say 'seems to' because it's only been about a week, although I have had several outages and no blank graphs.

Garry W. Cook, CCNA
Network Infrastructure Manager
MACTEC, Inc. - http://www.mactec.com/
303.308.6228 (Office) - 303.881.5157 (Mobile)


> -----Original Message-----
> From: Jason Lixfeld [mailto:jlixfeld at andromedas.com]
> Sent: Wednesday, July 17, 2002 7:52 AM
> To: mrtg at list.ee.ethz.ch
> Subject: [mrtg] Blank graphs
> 
> 
> 
> Greetings,
> 
> 	I've been using MRTG w/RRDTools just fine for a couple of months
> on a RedHat box running 2.4.11, but then all of a sudden my 
> graphs just
> started appearing blank.  I've checked a bunch of things and upgraded
> MRTG and RRDTool both to the latest versions but I still can't get the
> graphs working again.  I thought it may have been a load issue on the
> box it's running on as I have some other monitoring 
> applications running
> there aswell.  As a test, I commented out all mrtg config 
> file includes
> except for a config for graphing a few interfaces on one router --
> still, no dice.
> 
> I can restart mrtg with no errors or anything either in daemon mode or
> standard mode.  The data from the graphs is still present, so 
> if I click
> on one of the yearly graphs, I see the data just fine.  The .rrd files
> are all current aswell.
> 
> Can anyone else give me some insight on what to look for to try and
> solve this problem.
> 
> Thanks in advance.
> 
> Regards,
> --
> 
> Jason Lixfeld
> Senior IP Network Engineer
> Fastvibe Corporation
> 
> --
> 
> tel://416.341.0099:223
> fax://416.341.0088
> mailto:jlixfeld at fastvibe.com
> 
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