I have a firewall forwarding the port to my mail server. Do I still forward it to the "Master" server or do I forward to the "Slave" server. "Installing A Web, Email & MySQL Database Cluster On Debian 6.0 With ISPConfig 3" Is the slave just a mirror of the master in-case of failure? Or should the first stop in the port forward be the slave and then the master???? Does it matter?