CRM 2011 IFD : single URL instead of internal and external URLs ?

Hi,

Instead of defininginternalandexternalURLsfor access toCRM 2011 (IFD), I would like to knowhow to define asingle URLand :

1. whenthe user accessesbyinternal access, he isautomatically authenticatedby his accountand password
   
2. when theuser accessesfromthe outside, heisredirected tothe login pagein order to providehis account andpassword.

Thank youin advance foryour cooperation

Noureddine