Many thanks for your answers!
I'm not on site right, i'll plan to double check it on site.
Yes it is the admin page right.
To be sure :
You need at leat 2 policies ? the initial one and the authentification ?
If i understand, it's means that i can get access to the CP page because the initial role doesn't works.
For example, if i get access to the CP page authenticated and i cannot get acess to internet the Authentification role doesn't work.
Is it right ?
In my case, i've got the DNS error when i want to get access to internet but before the CP page...
I can get it thru the IP address...
Which role is it ? i'm little bit lost ...