Hi Davide,
You need to tell ONOS the INT collector IP address and port, the way to do that is to send the JSON config from my previous email.
You can use this command to push the config to the ONOS
curl --fail -sSL --user onos:rocks -X POST -H 'Content-Type:application/json' http://[your onos IP]:8181/onos/v1/network/configuration -...@int.json
Note that you need to replace "[Your ONOS IP]" with your ONOS IP address.
You also need to modify the "int.json" file since you can use a different IP address for your INT collector.
Yi