[rrd-users] Invalid Graph Data

Jason Frisvold Jason.Frisvold at corp.ptd.net
Mon Feb 25 15:50:18 MET 2002

Hi all,

	I'm not sure if this is an MRTG specific question, or an RRDTool
Specific question...  However, I think RRDTool has the functionality I
need to fix this, so I'll ask here first.

	I have MRTG retrieving the in/outoctets from an ATM switch.
It's a Marconi ASX-1000.  It seems to work fine.  The values are stored
in an .rrd, and then I have a custom program that displays the data.
However, I am experiencing a problem.  Once in a while, the traffic
spikes to some ridiculous amount.  Last time, it spiked to 5 Gig.  I'm
thinking about patenting the technology that lets me get 5 Gig via and
OC-3, but that's another story  ...  :-)  Anyways, these values are,
obviously, wrong.  The problem is that RRD creates the graphs and sets
the scale so these values are visible.  It's throwing the entire scale
off!  I know I can specify the upper-limit, but it seems that when I do
that, it always scales to that upper limit.  In some cases, that is a
problem as well.  We don't always max out the OC-3's and in some cases
have very little traffic on them.

	Is there some way with RRDTool to create the graph to ignore
these large spikes?  Is there some way to remove these spikes from the
existing .rrd's?  And does anyone have a suggestion as to why this is
happening to begin with?  The only thing I can think of is that it's
getting screwed up during a rollover...  But, I'm not completely sure if
that's the case...  I have MRTG set up with only the "unknaszero"
option...  I thought the default options handled rollovers?  And this
happens pretty rarely...  It's not something that happens on a

Jason H. Frisvold
Senior ATM Engineer
Engineering Dept.
CCNA Certified - CSCO10151622
friz at corp.ptd.net
"I love deadlines.  I especially like the whooshing sound they make as
they go flying by." -- Douglas Adams [1952-2001]

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