We have a two server multiserver setup with two webservers. The main server has an IPv4 address with several websites on it, main.example.com. The secondary one has only an IPv6 address and one website, other.example.com. They are part of the same internal network. I can't figure out how to configure the sites using ispconfig to have requests to other.example.com go to the webserver on other.example.com rather than main.example.com.