Device Down - False Positive

fmoreira86 · Post by **fmoreira86** » Mon Jul 28, 2014 10:25 am

Hello good people,

I've noted a strange behaviour with a set of devices.

I receive from times to times mail alerts saying that those devices are offline (though it goes online in matter of minutes).

It's strange because it doesn't look like to go offline.

I tried to do a constant ping running from my cacti server to those machines... and with that ping running I receive no mail alerts with false positives.

Any hints to debug this?

Thanks!

cigamit · Post by **cigamit** » Mon Jul 28, 2014 11:53 am

What type of device is it?
What is your "Downed Device Detection" set to for that device?
What are your various timeouts set to for that device?
Under Settings >> Poller, what is your Failure Count and Recovery Count set to?
Have you checked the logs and looked if Cacti reported a timeout to that device?

fmoreira86 · Post by **fmoreira86** » Mon Jul 28, 2014 3:07 pm

Those devices are two Ubiquiti AP, 1 Switch, etc...

Detection: Ping or SNMP Uptime (ICMP Ping)

Ping timeout 500
Ping Retry 3

Failure Count = 2
Recovery Count = 3

Log:

ERROR: HOST EVENT: Host is DOWN Message: SNMP not performed due to setting or ping result., ICMP ping Timed out

cigamit wrote:What type of device is it?
What is your "Downed Device Detection" set to for that device?
What are your various timeouts set to for that device?
Under Settings >> Poller, what is your Failure Count and Recovery Count set to?
Have you checked the logs and looked if Cacti reported a timeout to that device?

cigamit · Post by **cigamit** » Mon Jul 28, 2014 3:24 pm

Ok, so it is showing a Ping Timeout. Your 2 options are really to raise the Ping Timeout, or more preferably change the Down Host Detection to "Ping and SNMP Uptime" and see if that helps. It will still attempt SNMP after the Ping fails, and only alert if both fail.

I would also track down and try to determine why the Ping is failing to begin with. It could be they are slow to respond, or since it is multiple devices, it could be a device in between the cacti server and them that is causing it (network, firewall, etc..)

fmoreira86 · Post by **fmoreira86** » Mon Jul 28, 2014 3:35 pm

Same lan, no fws.

The odd thing is that this doesn't happen when I keep a continuous ping running.

Cacti

Device Down - False Positive

Device Down - False Positive

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