From OpenNMS

newSuspect events are generated by the Discovery Process using ICMP pings to the include-range and include-host lists in etc/discovery-configuration.xml. New suspects are then passed on to capsd for capability determination.

If the host you wish to monitor is not accessible by ICMP you can create your own newSuspects.

To generate newSuspects yourself:

WEB-CONSOLE > Admin > New Interface. Type in an IP address and it will be added to the list of hosts to consider (there must be a listening port on the host that ONMS understands for the host to be added. Watch your Events to see the state of play.)

You can also use a provided Perl script to do this from the command line eg:

bin/send-event.pl --interface 192.168.100.10 uei.opennms.org/internal/discovery/newSuspect

The above is correct for v1.2.2 and later versions. Previous versions used a different UEI, which can be found by looking for newSuspect in eventconf.xml