针对多个提供者的表单身份验证（SQl和AD）

We have an application that is for both internal users and external customers. We would like to authenticate against AD for the internal users and against sql membership for the external customers. Has anyone taken a similar approach? Also what is the best way to authenicate against AD when in a DMZ? I would rather have a proxy of some sort that is in the dmz and handles authentication against the AD DCs on our internal network. Any suggestions?We have an application that is for both interna