IP setting can be done temporary or persistent.
in the fist case, the interface must be plumbed in the following way:
# ifconfig nxge0 plumb
# ifconfig <intferface> <ip address> broadcast <bcast address> netmask <netmask>
If you want your configuration to persist across reboots you'd need to do the following... Each machine on a TCP/IP network gets its configuration information from the
following TCP/IP configuration files and network databases:
/etc/hostname.interface Read more...