Web site Maintenance Page MVC 3

Revision 2
Hi,

Can anyone tell me how re-direct to web site down Maintenace page in MVC3, so whenever users log in they should be re-directed to Maintenance down page, when site is down

Note :- Some users should be able to access the application for testing purpose, remaining all user should be denied access and redirected to Down page.
Authentication Used : Windows

Thanks
Vikram