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Traffic sensor, percentage erroneous calculation. Bug?



Hello team,

I asked this question about a week ago, because the percentage calculation in SNMP traffic sensor for Traffic In and Out channel is not working well.

I was advices to upgrade PRTG, since then I upgraded it twice, the last time was yesterday, upgraded to x64, but the problem persists


Sometimes when the GigabitEthernet reaches 5% of utilization for Traffic In, PRTG for some reason shows 332% of 900% for example..

I tried to delete SNMP traffic sensors and add them back, the percentage according to my settings changed well, but then suddenly showed this 332% alarm and the percentage (red alarm) jumped from 84% to 600%..

I have about 8 SNMP traffic sensors for 3 different devices that work like this and the Cisco 1900 routers have no difference to others (in IOS of configuration), nevertheless it happens..

Thank you.

channel percentage snmp-traffic-sensors traffic-sensor usage-percentage

Created on Feb 5, 2014 2:19:04 PM

5 Replies



From your screenshot it looks like you are setting up this channel with the setting to show in percent of the maximum and are then setting the maximum at .097 Gb which is likely why this is showing as 665%. You are also setting your error limit to 0.078125 Gb and if this is a Gigabit connection, this wouldn't be hard for the sensor to run over.

If you wanted to set the maximum to 1 gbit you would want to set up the channel to be a percent of 1048576 kbit.

Created on Feb 5, 2014 9:12:03 PM by  Greg Campion [Paessler Support]



Hello Greg, this screenshot is taken from Fa 100mbit interface, so the percentage of 102400 kbit/s is correct, based on 102400 the 80 and 60% is calculated correctly. I just checked one of my Gb interface and it shows 1048576 value as 100%

What would you suggest?

Created on Feb 6, 2014 1:48:43 PM



The best way to see why this is happening would be to check the values that are given out by SNMP. You can do this by running an SNMP interface scan with the SNMP tester and then take the OID for the inbound or outbound for one of the interfaces and set this up to scan on a similar interval as the PRTG sensor. Then compare the values you get in the SNMP tester to what is shown in PRTG. It may that SNMP is giving out false values from the device.

Created on Feb 7, 2014 1:57:24 PM by  Greg Campion [Paessler Support]



Greg, I understand, but the percentage calculation is independent from what SNMP is giving you. If you put 10 as your 100% part and then set 8 and 6 as threshold values, this is independent from SNMP, but local to PRTG or I am missing something?


Created on Feb 7, 2014 2:02:17 PM



If you put the 10 value as your max and 8 and 6 as your thresholds, the values given by SNMP will be judged by PRTG based on those so if SNMP returns 100, you will see spikes like you are seeing which happens from time to time because of bugs in the counters and things like that which is why I would recommend checking what is being given out by SNMP with the tester.

Created on Feb 7, 2014 2:59:44 PM by  Greg Campion [Paessler Support]

Last change on Feb 7, 2014 3:00:08 PM by  Greg Campion [Paessler Support]

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