I have added a new subnet on our network so we can add more wireless devices (iPads, Cellphones, etc. are all now needing IP addresses)

Everything is working fine except that the addresses are not releasing after 3 days. If someone with a Laptop comes into our building with a cell phone or laptop they are picking up an IP address automatically. Then once they leave (and the 3 day lease time expires) DNS/DHCP is not making that address available for another device.

Now we are quickly running out of local IP addresses on this new subnet. How can I get DNS/DHCP management console to hand out previously used expired IP addresses to new devices?

Thanks in advance!