Cluster

I would like to cluster my current ragnarok server to a new Valguero one for just me and my friends to play on however everything I read says that you can't password protect your servers when creating a cluster so I am very concerned about random people joining my servers and ruining it for us. Any help and advice is very much appreciated as I have searched all over for answers and turned up very little. Thanks

I'm aware they cause issues which is why I'm concerned about doing this, I am not able to monitor my servers constantly as I work fulltime as do my friends and we aren't on all that much. As for saying it's unlikely someone would join having played on nondedicated servers before renting one I can say from experience that people certainly do join random servers just to annoy and troll the other members which as we don't play often they would have ample opportunity to do so. Is there no way to secure my server at all so it is only accessible to those who I wish? If not then I'm very disappointed.