Some firewalls (CSF for instance) have a limit of maximum overall PING requests per second that your server can receive.

The default limit is set to 1/s, meaning one request per second, so if 3 or 6 of our monitors all ping your server at the same time, then some/most of them will fail due to this limit.

If you select PING monitoring type, then please remove or increase this limit in your CSF to avoid false alarms.

Here’s how you can raise or remove the PING per second limit in your CSF firewall:

1. Open “/etc/csf/csf.conf” with your favorite text editor
2. Find “ICMP_IN_RATE”
3. Either set it higher than 1/s (which is the default) or set it to 0 to remove the limit completely
4. Save the file
5. In SSH run: “csf -r” to reload the CSF configuration

You’re all done. Now all of our monitors will be able to properly ping your server.

* The above mentioned limit only applies to PING .You can safely monitor ports like HTTP 80 without any changes required on your server.
** If you cannot (or don’t want to) modify your server’s firewall, then you should monitor a port number in order to avoid false positives.

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