Address assignment from IP pools is based on Accounting Start and Stop records. A duplicate IP address might be assigned to a user if an Accounting Stop packet is received out of order following a new access request by the same user.
If ACS receives a late Stop packet, it might erroneously mark an IP address as free, even though it has just been assigned. That might lead to a duplicate address assignment during the next connection.Such situations can happen in DSL environments where a router starts new PPP connections in less than 1 second after a previous disconnection
