The problem is that it keeps using an IP address after the lease has run out and the address may have been given out to another device. The difference between u

The problem is that it keeps using an IP address after the lease has run out and the address may have been given out to another device. The difference between universities that see this problem and those that don't is probably that the latter assign the addresses for WLAN clients from a large pool (try 10.0.0.0/8) that allows them to keep the association between mac address and IP address for the whole term or even longer.