Start a non forking snmptrapd daemon accepting all incoming traps and logging them to standard output:
snmptrapd -CdfLo --disableAuthorization=yes
Send a testing trap to the host running snmptrapd daemon (in this example
10.0.0.1):
snmptrap -v 1 -c public 10.0.0.1 .1.3.6.1.6.3 "" 0 0 coldStart.0
Also make sure the host firewall is not blocking incoming UDP/162 traffic.