Logging anonymous and Active Dir users without login form

[pv]

Hi everyone,



I need help with following scenario, please:



Users are accessing same web server from intranet (users previously
authenticated in Active Dir) and from extranet (common public users). If
user is from intranet, web server should recognize it and application should
create additional options in controls regarding groups the user belongs to.
If user is from extranet it should be logged in as anonymous and a link to
login page should be created. The goal is to have login page only when user
request it.



I have tried to achieve this by using both windows and forms authentication
but I still did not find the way to avoid IIS login form.



Thanks in advance.

PV