I'm not a ClearPass expert but if you have a pair of CPPM devices make sure to think about the VIP address. Also you could have several different IP interfaces for data, some for internal clients and other for guest traffic, depending on your design. In my setup the CPPM IP's are also mentioned in the controller, for the purposes of pointing to the guest login page.
Anywho like the other poster mentioned, the auth is never based on the IP so I can't imgine your clients would need to authenticate again.