Open Stack

Hello,

does it possible assign IP when build VM? We have flat network setup
with DHCP=false, but i have created start/end IP range so openstack
assign IP when VM start.

Yesterday one of my application crash and i was planing to rebuild VM
with new OS, but problem is how do i assign existing IP?  that IP is
configured in all firewall,DNS, SSH key list etc.. it is total mess if
i change IP :(

can i grab old IP for that instance or just reserve that IP for that VM?