multiple ips with tomcat?

Hi

I's like to setup different webs with different ips
on one single server. does anyone know how to configure
that in the tomcat server.xml? if I use the <Host> tag
with a given host name and configure a context in that
<host>-tag with the path set to "" there appears always
a "No Context configured to process this request" error.

I use tomcat 4.0.4.

mike