when installing on multiserver, each server has a role. One control panel (solely CP!) that uses interfaces One or many other servers that do not have a control panel It doesn't make sense to install the server part on a pure CP, and it doesn't make sense to install interfaces on pure servers
So far that I know you'll only need to enable ISPConfig interface in the master server which is only one and other ISPConfig installations doesn't need the ISPConfig interface to be enabled. The ISPConfig installation on other servers is necessary to link them to ISPConfig master server database. Unless you mean to separate that master server and all other ISPConfig servers from their own database by using separate database server(s), that although not advisable, can already be achieved with some technical knowledge.
