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Nodes are split into groups of size fastping_node_poll and then fping is run on these sets, one after another. After all the pings are complete fpingd takes the results and updates the NMIS event table, when that is complete NMIS escalations are run and then the daemon will sleep for fastping_sleep + a random value between 0 and 10.
fastping_timeout is an important configuration variable when investigating ping loss, as any ping value higher than this number will be considered loss, 300 ms may be too low if you have a high latency network and are experiencing high ping loss on nodes that appear pingable.
Here is a table of the config variable and what it controls, these are all set in Config.nmis where you can find the default values:
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