It can take up to 6 minutes (or as little as 1.5 minutes) to determine that a host is offline. Hosts are checked, currently, every 5 minutes, and, failing a check, they are rechecked 1 minute later and if still unavailable, an event is generated.
One thing you might also want to confirm is that the device is pingable from the ON100 initially, you can do this via the tools icon towards the left side of the customer's Dashboard view.
Article ID:4018 Monitor Web Services on a Device on Cisco OnPlus Portal
Objective Event Monitors are mainly used to monitor the device in order
to provide notifications to the technicians in a timely manner if there
are any problems with the device perfor...
Article ID:3884 Monitor Duplicate IP on OnPlus100 Objective The
Duplicate IP monitor is one of the event monitors on the OnPlus100
device to check the network performance. Duplicate IP monitor checks
whether more than one device in the network uses the sa...
Article ID:3986 Monitor Host Performance with Internet Contol Message
Protocol (ICMP) for a Device on Cisco OnPlus Portal Objective Event
Monitors are mainly used to monitor the device in order to provide
notifications to the technicians in a timely manne...