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morbiddog2
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SNMP Data loss

Fri Mar 09, 2012 3:13 am

this problem occurs for me in dude 3.6 as well as the most recent 4.0 beta, I have also recreated it in a smaller instance of the dude monitoring only the afflicted devices

I am using packetflux site monitors for monitoring voltages at remote sites using snmp I have the device label set up to display the snmp values associated with voltage as well as custom data sources for voltage graphs. The problem is that the reported value will often drop to 0 when there is in fact still a consistent voltage. This happens on the label as well as on the data chart. The probe intervals are set to 1 minute with a 2 minute timeout and a 1 minute interval on the data sources I have tried all variety of times for all the settings and none of it seems to make a difference.

Please can anyone help me with this.

EDIT: I have so far been unable to recreate this problem in PRTG Network Monitoring Tool, all values report accurately with 30 second intervals.
 
lebowski
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Re: SNMP Data loss

Fri Mar 09, 2012 4:33 pm

Change the negative cache timeout. This will let the label return to normal after a failed read. As for the reason for failed reads there is some discussion on the beta 4 thread. It is not well understood but it is a known problem... hopefully they will decide to look into it.

Here is an example label for cisco wireless 2.4 ghz users...
Users:[oid("1.3.6.1.4.1.9.9.273.1.1.2.1.1.1",10 ,5)]
Notice the cache time of 10 seconds and the negative cache time of 5 seconds.

The description from the oid function...
returns value of given snmp OID. Only first parameter mandatory. First parameter - oid string, second - cache time - default 5 seconds (5.0), third - negative cache time - default 5 minutes (300.0), forth - ip address (overrides context device), fifth - snmp profile (overrides context device)

I believe the negative cache time should not be set in the first failed read which is what is happening. I can't think of any good reason for negative cache time except for forcing a failed device off the network so you won't hear from it again for a while.

HTH
Lebowski.
 
morbiddog2
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Re: SNMP Data loss

Fri Mar 09, 2012 10:20 pm

Thanks for the reply you were able to resolve almost all of my issues and its much appreciated, however, I'm still having one issue. On the output graph for these snmp data sources there are periodic drops to zero, i have done the same thing to the oid on the data sources but it did not completely resolve the issue. Furthermore when i open the individual graphs of the data sources many of these drops don't appear. Any thoughts?

Thanks again
 
lebowski
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Re: SNMP Data loss

Sat Mar 10, 2012 12:26 am

I am stumped...

The things that screwed me up the most is the "available" line being "true" when it should not be. Always use 0 or "False" as your comparator in an available line otherwise a probe with a broken available line would install on any device.

When the value returned by SNMP is actually 0 the probe shows down, get around this by adding 1 then subtracting 1 later.

If you look for probes based on functions and using the function to do your collection you can have a probe that complains when it can't read the data and a complains when the data is not within specification. Any of the newer probes I have posted will be function based.

Also search for gsandul's posts he hasn't been around but he wrote some great stuff.

Glad that it is working better.
Lebowski.
 
odge
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Re: SNMP Data loss

Mon Aug 27, 2012 4:19 pm

Is there a way to make other funtions have cache.

For example a function that executes a command, may be called more than once, but it isn't necessary to call the command so many times.

I cant seem to get my output to be treated as an integer, and so I can't functionlise it (i always ends up = 0), but if I used it directly in a prove it works.
 
digicomtech
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Re: SNMP Data loss

Mon Nov 19, 2012 5:12 pm

Hi,
I don't know if someone else got the problem, but on some device (often RB493G) the voltage monitor stop to work. /system health show 0.0 V value, so voltage probe failed even if snmp seems to work as in the snmp tab in the dude interface is still showned.

Any idea ?

Regards,

Michael

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