[mrtg] Re: dealing with transient interfaces, and adding several transients, how to ?

[Kruepke]

I can answer one of your questions.

To zero out sections of a graph (after the fact), check out http://buckaroo.xo.com/MRTG/ for some MRTG helpers by Matt Petach.  He has a script that will zero out sections of a log file.  Check it out.

Unfortunately, that solution will only work by manually running it after a transient interface comes back up.  I think the "horizontal line syndrome" from interfaces being down/unavailable is a design decision and cannot be changed in the config.  (Someone correct me if I'm wrong...)  However, since MRTG is open source, one of its powers is that you can get it to do anything you want.  I'm sure it is possible to find the code that deals with SNMP errors and change that to make those data points zero.  I know this is extra work, but sometimes hard work is the only way to harness the power of open source.

As far as getting MRTG to look for all (up to the max) interfaces dynamically, I doubt that functionality exists.  One option would be to run a hacked cfgmaker script to generate the config for those interfaces dynamically.  Another option depends on the response that you get.  If you get an error message from the device, then you know that interface is not up at that time.  (This may not be ideal, but it is faster than waiting for a timeout.  I'm not sure if MRTG retries in this case, but you can change the retry value.  If the device just doesn't answer, you can specify a lower timeout and prevent it from retrying.

I hope some of this input helps.

Keith

----- Original Message ----- 
From: "Voytek Eymont" <voytek at sbt.net.au>
To: <mrtg at list.ee.ethz.ch>
Sent: Sunday, April 16, 2000 8:33 PM
Subject: [mrtg] dealing with transient interfaces, and adding several transients, how to ?


I have a system acting as a 'terminal server', it's a PC with multi i/o
cards and a bunch of analogue modems attached to com ports.

I would like to mrtg all these PPP sesions, individually, and, all together
as well.

 *when* there are calls/PPP sessions estabilished, mrtg can see
these 'transient' interfaces, and, charts them properly.

trouble is,, IF an interface is running at, say, 1000 b/s, and, at next
pass, after 5 minutes, the session is disconnect/gone, then, on subsequent
passes, mrtg doesn't see that i/f, UNITL another PPP sesion is
estabilished, then I end up with a horizontal 1000 b/s line in between
these two sessions.

is there a way to 'drop' reading to zero when an interface 'dissapeared',
rather, than 'extrapolate' it at last know reading ....?

also, my 'SUM of I/F' fails to chart, unless all targets exists, is there a
way to sum up 'only the i/f that exist, up to maximun of all exists ?

mrtg 2.8.8

mrtg.ppp has:
=========================
# this charts OK
Target[ts.sbt.net.au]: 1:my-pass at ts.sbt.net.au
MaxBytes[ts.sbt.net.au]: 1250000
Title[ts.sbt.net.au]: echidna.sbt.net.au (ts.sbt.net.au): DIX+802.3
PageTop[ts.sbt.net.au]: <H1>Traffic Analysis for DIX+802.3
 </H1>
 <TABLE>
   <TR><TD>System:</TD><TD>ts.sbt.net.au in Chippendale,
NSW</TD></TR>    <TR><TD>Maintainer:</TD><TD>admin at sbt.net.au</TD></TR>
   <TR><TD>Interface:</TD><TD>DIX+802.3 (1)</TD></TR>
   <TR><TD>IP:</TD><TD>ts.sbt.net.au (203.41.6.3)</TD></TR>
   <TR><TD>Max Speed:</TD>
       <TD>1250.0 kBytes/s (ethernetCsmacd)</TD></TR>
  </TABLE>

#---------------------------------------------------------------
# this doesn't chart
Target[ts.sbt.net.au.ppp]: 2:my-pass at ts.sbt.net.au
  + 3:my-pass at ts.sbt.net.au
  + 4:my-pass at ts.sbt.net.au
+ 5:my-pass at ts.sbt.net.au
  + 6:my-pass at ts.sbt.net.au
+ 7:my-pass at ts.sbt.net.au
MaxBytes[ts.sbt.net.au.ppp]: 28800
Title[ts.sbt.net.au.ppp]: echidna.sbt.net.au (): Serial Interface ppp0-ppp6
PageTop[ts.sbt.net.au.ppp]: <H1>Traffic Analysis for All Serial Interfaces ppp0-ppp6
 </H1>
 <TABLE>
   <TR><TD>System:</TD><TD>ts.sbt.net.au in Chippendale,
NSW</TD></TR>    <TR><TD>Maintainer:</TD><TD>admin at sbt.net.au</TD></TR>
   <TR><TD>Interface:</TD><TD>All Serial Interfaces ppp0-ppp6 </TD></TR>
   <TR><TD>IP:</TD><TD> ()</TD></TR>
   <TR><TD>Max Speed:</TD>
       <TD>28800.0 Bytes/s (slip)</TD></TR>
  </TABLE>

#---------------------------------------------------------------
# this charts OK WHEN that session exist

Target[ts.sbt.net.au.2]: 2:my-pass at ts.sbt.net.au
MaxBytes[ts.sbt.net.au.2]: 4800
Title[ts.sbt.net.au.2]: echidna.sbt.net.au (): Serial Interface ppp0
PageTop[ts.sbt.net.au.2]: <H1>Traffic Analysis for Serial Interface ppp0
 </H1>
 <TABLE>
   <TR><TD>System:</TD><TD>ts.sbt.net.au in Chippendale,
NSW</TD></TR>    <TR><TD>Maintainer:</TD><TD>admin at sbt.net.au</TD></TR>
   <TR><TD>Interface:</TD><TD>Serial Interface ppp0 (2)</TD></TR>
   <TR><TD>IP:</TD><TD> ()</TD></TR>
   <TR><TD>Max Speed:</TD>
       <TD>4800.0 Bytes/s (slip)</TD></TR>
  </TABLE>


#---------------------------------------------------------------

# several more as above

Voytek Eymont
SBT Information Systems Pty Ltd
http://www.sbt.net.au/links/
phone +61-2 9310-1144 fax +61-2 9310-1118 

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