Thank you very much Christian.

Now we understand more precisely how remote nodes are launched.
Adding the ROS_HOSTNAME vairable to the machine file solved the issue.
This is how it looks like now:
> <launch>
> <machine name="fugu-c" address="fugu-c.local" user="user"
>            ros-root="/opt/ros/diamondback/ros/"
>            ros-package-path="/home/user/ros:/opt/ros/diamondback/stacks" >
> <env name="ROS_HOSTNAME" value="fugu-c.local" />
> </machine>
> </launch>

Following Tully's advice, I am going to repost the questions to 
answers.ros.org,
with a link to this thread, to help spread out the answer.

Thanks again!

-- 
Joan Pau Beltran
Grup de Sistemes, Robòtica i Visió - DMI
Universitat de les Illes Balears