[mrtg] Re: Strange spikes with summer (router0 + router1) traffic

[Matt Walkowiak]

Do you happen to be monitoring any switches or other network devices on the
same mrtg box that you are getting spikes on the summed graphs?
My mrtg box graphs mostly switch ports - I mainly do it to catch hackers and
run-away network connections.  Anyway, SOMEtimes, when mrtg will not be able
to see a particular switch, it will graph spikes on every port of the
switch, as long as there is something plugged into the port (my .cfg files
monitor every port even if they are empty...)  Some times it happens to
every device that I monitor (like the time when the eth0 interface was
accidentally stopped for a few hours, when I started it up again, mrtg ran
and graphed spikes on ALL devices) and sometimes it happens to only one
device, which for some reason didn't respond.

Anyway, I was just wondering if you saw the spikes on other equipment also.

Matt

-----Original Message-----
From: Bill Wichers [mailto:billw at waveform.net]
Sent: Monday, May 21, 2001 11:37 AM
To: mrtg at list.ee.ethz.ch
Subject: [mrtg] Strange spikes with summer (router0 + router1) traffic



I'm seeing these strange spikes in some summed graphs (two routers added 
together with the + in the config). The usual traffic is in the several 
hundred k range on each router, but occasionally there will be huge spikes 
to 48 Mb and other very high numbers even though the graphs of the two 
routers seperatly do not show this much traffic when added together by 
hand. I have another summed graph of a router port and an SNMPd port on a 
UNIX box that behaves in a similar way, but the spikes do not line up 
time-wise between the router+router and router+server graphs.

Most of the time the graphs show the correct traffic amounts, but it looks 
like occasionally there will be a single sample to many megabits and then 
it goes back to normal. This is on MRTG 2.9.10 running on a Redhat Linux 
7.0 box (with some of their patches installed). Does anyone have any idea 
what might be causing these spikes and any suggestions for a possible fix?

	-Bill


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