Some more informations,

My goal is to find a technic to keep the different directives as it is,
and to surround them with a proxy or something like that. I want to
avoid to duplicate all the directives. I don't want a directive from
intranet and another one for this range of address.

The authentication is "just" to validate the incoming user. All those
incoming users are registered within a central ldap server.

Bruno