Open Stack

I'm working with OpenStack Grizzly, and I'm looking to be able to remove
an assigned IP address and reassign it fairly quickly (in the course of
several seconds). However, it looks like Grizzly will hold on to an IP
address in accordance with the DHCP lease time. Right now, my solution
is to delete the row from the ipallocations table, but this doesn't
quite work. I believe that I need to modify the ipavailabilityranges
table as well in order to get it to work. It seems like there should be
a better way to do this, though. Is there some way of manually freeing
up an IP address and reassigning it?