I have been playing with Nexenta GNU/OpenSolaris to get familiarized with dtrace. This document is a good explanation of how to configure the system with a fixed IP address: docs.sun.com: System Administration Guide: IP Services
I would add the following: if the system is currently configured to use DHCP, you also have to remove the corresponding /etc/dhcp.* files for the interfaces you want to set with a fixed IP address.