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False ping errors: Socket Error # 11001 Host not found

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On regular bases I get these false ping errors, as whenever I get the message I immediately go over to the PRTG server and ping from there without any problems. Usually the ping returns after 10-15 minutes. Since I can ping the hosts from the PRTG server, there does not seem to be any configuration problems (number of pings, response times etc.) I used to have no problems, it started about a few months ago after one of the updates of the PRTG monitor (I'm using the latest version now).

ping ping-error ping-sensor

Created on Jul 12, 2017 7:32:20 AM by  gesture (50) 1 1



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Hi there,

Is there an AntiVirus System installed on the same system? If so, please disable it temporary and observer the behavior. Some AVs are blocking automated ping requests. This could also be caused by a firewall.

Are only certain devices/sensors occurred? If so, then please open a commandline on the Core Server and issue ping for two or three of the affected hosts (ping -t HOST).

Best regards.

Created on Jul 13, 2017 2:23:24 PM by  Dariusz Gorka [Paessler Support]



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No firewall, devices are random as is the failing of the ping.

Best regards.

Created on Jul 14, 2017 6:43:10 AM by  gesture (50) 1 1



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Hi there,

Have you followed my advice by opening a commandline console with a constant ping? If so, where you able to see the same behavior as in PRTG?

Best regards.

Created on Jul 17, 2017 8:35:39 AM by  Dariusz Gorka [Paessler Support]



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I am having this issue.

This is not a ping issue, this is a 'host not found' issue. Meaning DNS is not resolving (as far as I can tell). And, for me also it resolves itself in 10-15 minutes.

We did recently install Carbon Black.

Created on Oct 15, 2018 4:05:48 PM by  SupAdmin (40) 1



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Hi there,

When PRTG complains about "host not found", does a NSLOOKUP of that hostname work manually on the PRTG Server?

Best regards.

Created on Oct 15, 2018 4:07:23 PM by  Dariusz Gorka [Paessler Support]



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Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.