In this scenario, if the user is connected for 15 minutes and then left, their IP address would still be associated with their device in the DHCP lease table.
Even if the user is offline, the DHCP server will keep the IP address reserved for the duration of the lease time (3 hours). During this time, no other device can be assigned that specific IP address.
Once the lease time expires (in this case, 3 hours after the initial assignment), the DHCP server will mark the IP address as available and it can be assigned to a new device that requests an IP address.
The Fortinet Security Fabric brings together the concepts of convergence and consolidation to provide comprehensive cybersecurity protection for all users, devices, and applications and across all network edges.