[mrtg] Measuring RSSI

McDonald, Dan Dan.McDonald at austinenergy.com
Wed May 6 19:34:44 CEST 2015

From: Steve Shipway <s.shipway at auckland.ac.nz<mailto:s.shipway at auckland.ac.nz>>
Date: Tuesday, May 5, 2015 at 6:26 PM
To: Rick Silacci <rick at velociter.net<mailto:rick at velociter.net>>, "mrtg at lists.oetiker.ch<mailto:mrtg at lists.oetiker.ch>" <mrtg at lists.oetiker.ch<mailto:mrtg at lists.oetiker.ch>>
Subject: Re: [mrtg] Measuring RSSI

You’re returning the SNMP OID rssi.0

Can you do an SNMPwalk from the command line, and retrieve this – it may be that the OID returns the value as a positive integer, or in a different form to how you expect?  You may need to modify your Target line to do some sort of post-processing (for example, some devices return temperature as an integer in centidegrees Celsius, and so need to be divided by 10 (or even converted to Farenheit in certain unenlightened countries:))

You do not give the entire MRTG configuration stanza here for comparison, but I’ve seen it in a separate communication, so I can verify that you do not have the ‘bits’ option enabled (which would multiply by 8).

More than likely, the units are centiBels.  You can fix that for display using Factor[] 0.1

Also, by default, MRTG assumes positive values.  If using RRDTool as the backend, you need to manually tune the .rrd file to allow negative values; I think they might be rejected by native mode MRTG.

Correct.  I have to tune my radio readings with:
for k in *signal.rrd ; do rrdtool tune $k –I ds0:-800 –I ds1:-800; done


Steve Shipway
s.shipway at auckland.ac.nz<mailto:s.shipway at auckland.ac.nz>
(GNU Terry Pratchett)

From: mrtg [mailto:mrtg-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch] On Behalf Of Rick Silacci
Sent: Wednesday, 6 May 2015 11:11 a.m.
To: mrtg at lists.oetiker.ch<mailto:mrtg at lists.oetiker.ch>
Subject: [mrtg] Measuring RSSI

I’m using the parameters below to measure rssi.  I’m supposed to be getting a negative number expressed in decibels, but this is what I’m getting:

Variable Name: RSSI
Variable Description: Radio Signal Strength
IndexSNMP/MRTG Variable Name rssi.0
Example: Target[Var]:rssi.0&rssi.0:Canopy at MyDevice:::::2

[cid:image001.png at 01D087EF.84044430]

Rick Silacci
Velociter Wireless
1525 Second Street
Escalon, CA 95320
Office: 209.838.1221
Phone: 209.838.1800

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