Configure the web portal on one interface, configure self-service on secondary interface

How can I configure the web portal to work only on one interface, and have the web portal listen on a secondary interface?

I have all other samba / ntp / services listening on both which I still need.

This is an apache2 configuration but I just cant figure out what to adjust to make all of /var/www/univention/self-service to listen on the secondary interface, while all other directories to listen on the other interface