>Is there another possibility to reassign the same ip-address to the user again?
Not while first connection is still active. That can't possibly work. NAS will reject such IP. Are you trying to create a multilink? That is NAS, not radius capability. Ivan Kalik Kalik Informatika ISP - List info/subscribe/unsubscribe? See http://www.freeradius.org/list/users.html

