Thanks for your answer Fulvio.
Well, finally I got it working. There was a very strange hardware problem with one NIC. I changed it and everything started working.
However, is not perfect (I’m still in beta5. I’ll post my results here after trying with beta6). Quite often, after a restart of one box, I have to restart two or three more times, the same box (not the other), in order to get it working.
This is not an Internet-related problem cause, when it occurs, I’m not able to ping Zeroshell box even from the same LAN.
By the way, I write my conclussions for my other questions:
* Is not necessary to have more than one certificate at each zeroshell box.
* Is not necessary to assign IP configuration to VPN tunnels before making the bond.
* Is not necessary to assign IP configuracion to the bond before making the bridge