> Keep it simple.  Zero traffic and zero data should graph as a zero,
> not the last value.
> 
IMHO you are right about this however it does not describe your
problem. What you are saying is that if you know the data to be
zero, graph zero. No argue about that. In your case, you don't
know that the data is zero because you don't get a response.
MRTG will in that case use the last known value. Don't get me
wrong, I don't think it is the right way to go.

Most likely you have no lines that can actually go zero. For me,
zero has no special meaning. Sadly, if the last known value actually
*was* zero, I don't notice any problems by looking at the graphs
alone, I really must read my mail. (are there still people using
that horrible ">/dev/null 2>&1" ?)

Tobi already responded and recommended to use rrdtool for these
kind of wishes. I partially agree with this however I do understand
that many people would be *very* glad if someone could write an
interface from mrtg to rrdtool (as it now interfaces with rateup)
thus being able to migrate slowly.

A quick workaround for you: Poll the device using an external script,
let the script handle any timeouts or other problems by returning
the values from the 1st line in the mrtg log (and the current time).
Warning: unchecked code. Just ment as a starting point:

---cut-here---
#!/bin/bash
set `snmpget router public 2.2.1.ifInOctets.1 2.2.1.ifOutOctets.1 || echo $?`
if [ $# -ne 6 ]
then
	set `head -1 mrtg.log`
else
	set `echo noop $3 $6`
fi
DATE=`date +%s`
echo $DATE $2 $3
---cut-here---

Regards,
Alex

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