Problem solved:
Even if you don't want to use secure connection, the port 7711 MUST be reachable and WILL BE USED. Also while 7611 is listening in ALL the IP addresses of the BAM server, 7711 is only listening in the configured management IP.
Since this two features are not documented (yet), it's worthy to mention here for other people that could face a similar issue. Thanks to WSO2 team for the support.