by logan » Feb 12 09 4:43 pm
Having the client actually call up the DHCP server and cancel it's lease sounds like an awesome idea in theory, but unfortunately, to maintain interoperability between devices (i.e. supporting every serving all the other DHCP enabled devices in the world), you have to adhere to the practices and functionality already defined by the DHCP RFC. To think outside the box or add more functionality would require defining a new DHCP protocol which would then break interoperability with existing DHCP enabled servers and devices. This is the dillema of the established internet I'm afraid.
In saying that, what you COULD try is shortening the lease times. I think, by default, WinGate will hold a lease for 30 days. This means if a client gets an IP from WinGate, that client effectively owns that IP for 30 days and it won't be offered to any other clients. If the client leaves the network, and somebody else manually assigns that clients IP, then the new client with the manual IP will be seen as the original computer that obtained the DHCP lease by WinGate.
If you shorten the lease time to 1 hour, then after an hour is up and the client leaves the network, that IP address is then free to be used by somebody else. Ultimately, as long as all the clients use DHCP and none are set manually (or at least make sure the IP's that are manually assigned are exempt from DHCP in WinGate) then there should be no problems at all since WinGate will keep track of all the IP's it's assigning ;).