Linux, how to ask DHCP to assign a specific IP address
Solution 1:
posting a section of debian man page for dhclient.conf :
fixed-address ip-address;
The fixed-address statement is used
to set the ip address of a particular
lease. This is required for all
lease statements. The IP address
must be specified as a dotted quad
(e.g., 12.34.56.78).
so by modifying /etc/dhclient.conf you should be able to request a fixed IP if the dhcp server doesn't reject such request.