DHCP and IP Numbers ?

Hi ! I have a question about how DHCP is working. You see, I try to set up a small cluster of boxes to do some parallel computing. The Name Resolution in this cluster is supposed to work with DHCP. Things seem to run smoothly, but after some time, my parallel process is interrupted, with no error message at all. I `d like to know if DHCP reassigns new IPs after a certain amount of time and if this could interrupt my parallel processes (I tried both MPICH and rsh). Any suggestions ? Thanks, Jörg