Hi you all,
== this is not a question, but an answer ==
I went through an issue, in order to help others who might had the same problem I'm writing down the problem description and the solution. Actually I found the solution while writing the "question" e-mail.

TL;DR:
Ibr-dtn nodes discover each other but do not ping, neither send to another ?
Make you sure you stopped the service: #service ibrdtnd stop


When you dtnsend, if the service is running, in the same time that your dtnd -i <nic>, the dtnsend use the service and then, maybe, the wrong interface and the wrong configuration file -as far as I understand-. Make sure you're using your own conf file with dtnd command (and the option -c <path to conf file>) and the right interface by shutting down the service.

Environment:

I do not know if it worth adding this in the FAQ, that's up to you to choose.

Have a nice day!