Ntop probing alerts

[Ofloo]

I get a lot of these messages:

1491471007|1|3|10|Probing or server down: [ .......](/lua/host_details.lua?host=192.168.1.40&ifname=igb2)
``` [Anyone any idea's what could be wrong?](/lua/host_details.lua?host=192.168.1.40&ifname=igb2)